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• Troubleshooting an unstable internet connection

  - by Konrad Rudolph

  My MacBook Pro running OS X (10.9, but I had the same problem before) is connected to a Belkin router via WiFi and, using Virgin Media as the ISP, to the internet. The connection is extremely unstable – on some days, I get a ping timeout every few seconds. In addition, some domains seem to suffer general connectivity issues. For instance, I often find that while the youtube.com website loads, none of the videos (which are hosted on a separate domain) do. At other times, videos load but always fail to buffer, even though the actual connection speed is ok, even though I’ve disabled dash playback. Since I’m living in a rented room and the ISP contract isn’t actually mine I’ve got only limited possibilities of addressing the problem. In particular, I have no access to the router configuration and my non tech savvy landlady, while sympathetic, is not in a great hurry to hand the problem over to the ISP’s customer support. What’s more, I seem to be the only person in the house experiencing these problems – but I can imagine that this is simply because I’m the only one who’s using the internet continuously. I’m searching for specific tests that might be able to pinpoint – and ideally solve – the problem. So far all I’ve managed to do is establish that Virgin is routing my traffic in mysterious ways. Here’s an excerpt from traceroute google.co.uk. It’s worth mentioning that the host name doesn’t seem to matter a lot, the trace route is always the same. traceroute: Warning: google.co.uk has multiple addresses; using 62.254.36.148 traceroute to google.co.uk (62.254.36.148), 64 hops max, 52 byte packets 1 (192.168.2.1) 1.112 ms 1.300 ms 2.359 ms 2 10.100.32.1 (10.100.32.1) 11.926 ms 10.217 ms 24.987 ms 3 cmbg-core-1a-ae3-610.network.virginmedia.net (80.1.202.93) 28.809 ms * 66.653 ms 4 popl-bb-1b-ae16-0.network.virginmedia.net (212.43.163.141) 13.759 ms 126.504 ms 20.472 ms 5 nrth-bb-1b-et-010-0.network.virginmedia.net (62.253.175.57) 28.357 ms 16.398 ms 42.387 ms 6 nrth-bb-1c-ae1-0.network.virginmedia.net (62.253.174.110) 27.441 ms 15.622 ms 12.044 ms 7 lutn-icdn-1-ae0-0.network.virginmedia.net (62.253.175.82) 16.678 ms 28.463 ms 28.253 ms 8 * * * 9 * * * 10 * * * ^C If I let it, this goes on until the end of time. It never seems to reach a destination. Is this normal? A friend living in the same town who is also with Virgin Media has a more conventional traceroute output: 7 hops to google.co.uk, all of which send the ICMP TIME_EXCEEDED response. The obvious fix – rebooting the router – doesn’t seem to help. As far as I can tell, the WiFi connection is stable (I can always ping the router) so the problem is further downstream. I’ve tried using an alternative DNS before (OpenDNS) but if anything, this made things worse. In fact, it made all Google services nigh unreachable.

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• Issues connection to Ubuntu via PuTTy

  - by user1787262

  I'm not sure this is the appropriate stack exchange site to post this question on. If not, please flag this for migration. I am trying to use PuTTy ssh into my ubuntu machine which is wirelessly connected to the same network. I originally ran ifconfig to get my ubuntu machines private network IP address. I then verified that ssh was running, I even ssh'd into my school network and then into the ubuntu machine itself. No problems yet. On my windows 8 machine I ran ipconfig to get my private network IPv4 address. I then pinged my ubunty machines IP and 100% of packets were received. I figured, "OK we are ready to use PuTTy to connect to my Ubuntu Machine". Keep in mind this was my first time using PuTTy. I tried entering the IP of my ubuntu machine in the PuTTy Config GUI but I got a connection timeout. At this moment I don't really know what's going on, SSH is running on port 22 of my Ubuntu machine and I can ping the machine why is it not connecting? (I tried [username]@ip too). So I went on my Ubuntu machine and ran nmap -sP 192.168.0.1/24 and found that my windows machines IP did not show up, the host is down. I'm at a lost in something I am not very familiar with. Would anyone be able to help me or direct me to some resources that would trouble shoot my problem? Thank you EDIT (ADDITION): tyler@tyler-Aspire-5250:~$ nmap -v 192.168.0.123 Starting Nmap 6.40 ( http://nmap.org ) at 2014-06-06 01:56 MDT Initiating Ping Scan at 01:56 Scanning 192.168.0.123 [2 ports] Completed Ping Scan at 01:56, 3.00s elapsed (1 total hosts) Nmap scan report for 192.168.0.123 [host down] Read data files from: /usr/bin/../share/nmap Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn Nmap done: 1 IP address (0 hosts up) scanned in 3.14 seconds tyler@tyler-Aspire-5250:~$ nmap -Pn 192.168.0.123 Starting Nmap 6.40 ( http://nmap.org ) at 2014-06-06 01:56 MDT Nmap scan report for 192.168.0.123 Host is up (0.022s latency). Not shown: 998 filtered ports PORT STATE SERVICE 2869/tcp open icslap 5357/tcp open wsdapi Nmap done: 1 IP address (1 host up) scanned in 72.51 seconds

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• Constructing radiotap header and ieee80211 header structures for packet injection

  - by hektor

  I am trying to communicate between two laptop machines using Wifi. The structure of the radiotap header and ieee80211 header I am using is: struct ieee80211_radiotap_header { unsigned char it_version; uint16_t it_len; uint32_t it_present; }; /* Structure for 80211 header */ struct ieee80211_hdr_3addr { uint16_t frame_ctl[2]; uint16_t duration_id; unsigned char addr1[ETH_ALEN]; unsigned char addr2[ETH_ALEN]; unsigned char addr3[ETH_ALEN]; uint16_t seq_ctl; }; struct packet { struct ieee80211_radiotap_header rtap_header; struct ieee80211_hdr_3addr iee802_header; unsigned char payload[30]; }; /* In main program */ struct packet mypacket; struct ieee80211_radiotap_header ratap_header; struct ieee80211_hdr_3addr iee802_header; unsigned char addr1[ETH_ALEN] = {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF}; /* broadcast address */ unsigned char addr2[ETH_ALEN] = {0x28,0xcf,0xda,0xde,0xd3,0xcc}; /* mac address of network card */ unsigned char addr3[ETH_ALEN] = {0xd8,0xc7,0xc8,0xd7,0x9f,0x21}; /* mac address of access point i am trying to connect to */ /* Radio tap header data */ ratap_header.it_version = 0x00; ratap_header.it_len = 0x07; ratap_header.it_present = (1 << IEEE80211_RADIOTAP_RATE); mypacket.rtap_header = ratap_header; /* ieee80211 header data */ iee802_header.frame_ctl[0] = IEEE80211_FC0_VERSION_0 | IEEE80211_FC0_TYPE_MGT | IEEE80211_FC0_SUBTYPE_BEACON; iee802_header.frame_ctl[1] =IEEE80211_FC1_DIR_NODS; strcpy(iee802_header.addr1,addr1); strcpy(iee802_header.addr2,addr2); strcpy(iee802_header.addr3,addr3); iee802_header.seq_ctl = 0x1086; mypacket.iee802_header=iee802_header; /* Payload */ unsigned char payload[PACKET_LENGTH]="temp"; strcpy(mypacket.payload , payload); I am able to receive the packets when I test the transmission and reception on the same laptop. However I am not able to receive the packet transmitted on a different laptop. Wireshark does not show the packet as well. Can anyone point out the mistake I am making?

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• WinXP - Having trouble sharing internet with 3G USB modem via ICS

  - by Carlos Nunez

  all! I've been banging my head against a wall with this issue for a few days now and am hoping someone can help out. I recently signed up for T-Mobile's webConnect 3G/4G service to replace the faltering (and slow) DSL connection in my apartment. The goal was to put the SIM in one of my old phones and use its built-in WLAN tethering feature to share Internet out to rest of my computers. I quickly found out that webConnect-provisioned SIMs do not work with regular smartphones, so I was forced to either buy a 4G-compatible router or tether one of my old laptops to my wireless router and share out that way. I chose the latter, and it's sharpening my inner masochistic self by the day. Here's the setup: GSM USB modem (via hub), ICS host - 10/100 Mbps Ethernet NIC, ICS "guest" - WAN port of my SMC WGBR14N wireless router in bridged mode (i.e. wireless access point). Ideally, this would make my laptop the DHCP server and internet gateway with the WAP giving everyone wireless coverage. I can browse internet on the host laptop fine. However, when clients try to connect, they get a DHCP-assigned IP from the laptop and are able to use the Internet for a few minutes before completely dying. After that happens, they are able to re-associate with the WAP and get IP addresses, but are unable to use Internet or resolve IP addresses until the laptop and router are restarted. If they do get access, it's very, very slow. After running Wireshark on the host machine, it turns out that this is because every TCP connection keeps getting RST. DNS seems to work. I would normally think the firewall is the culprit here, but when it drops packets, it drops them completely. The fact that TCP connections are being ACK'ed by the destination rules that out. Of course, none of the event Log isn't saying anything about what's going on. I also tried disabling power management on the NIC, since that's caused problems in the past; that didn't help either. I finally disabled receive-side scaling as per a Microsoft KB (that applied to Windows Server 2003, SP2) to no avail. I'm thinking of trying it with a different NIC (will be tough; don't have a spare Ethernet NIC around for the laptop), but I'm getting the impression that this simply doesn't work. Can anyone please advise? I apologise for the length of this post; all contributions are much appreciated! -Carlos.

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• Tomcat can't talk to MySql after outage

  - by gav

  I missed a payment for my server and hey suspended my account for a day or so. When they brought the server back up all my data was in tact but for some reason Tomcat can't make a JDBC connection to my MySql server. They both run on the same machine and hence I have a bind address of 127.0.0.1. It's strange because I have reset the machine of my own accord before without issue but clearly something has been reset in the downtime. I followed this guide (Just the bits which don't concern S3, I am not on Amazon infrastructure) originally and everything worked as expected. I'm very new to being a SysAdmin and I'm not sure what to try, how would you go about diagnosing this issue? The stack trace I get is as follows; INFO: Deploying web application archive myapp-1.1.war 2010-05-26 22:07:22,221 [main] ERROR context.ContextLoader - Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'messageSource': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'hibernateProperties' while setting bean property 'hibernateProperties'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hibernateProperties': Cannot resolve reference to bean 'dialectDetector' while setting bean property 'properties' with key [hibernate.dialect]; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dialectDetector': Invocation of init method failed; nested exception is org.springframework.jdbc.support.MetaDataAccessException: Could not get Connection for extracting meta data; nested exception is org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) at org.codehaus.groovy.grails.commons.spring.ReloadAwareAutowireCapableBeanFactory.doCreateBean(ReloadAwareAutowireCapableBeanFactory.java:129) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:450) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:290) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:287) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193) at org.springframework.context.support.AbstractApplicationContext.initMessageSource(AbstractApplicationContext.java:714) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:404) at org.codehaus.groovy.grails.commons.spring.GrailsWebApplicationContext.refresh(GrailsWebApplicationContext.java:153) ... I get this error for a number of 'beans'. If I type mysql at my command prompt then I can easily login with the same credentials as my grails app which uses GORM and Hibernate to persist objects to the DB. I might not have given enough info to start with but I'm really interested to learn and will certainly provide it if asked, I just really don't know where to start on this one. Thanks, Gav

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• Solution to route/proxy SNMP Traps (or Netflow, generic UDP, etc) for network monitoring?

  - by Christopher Cashell

  I'm implementing a network monitoring solution for a very large network (approximately 5000 network devices). We'd like to have all devices on our network send SNMP traps to a single box (technically this will probably be an HA pair of boxes) and then have that box pass the SNMP traps on to the real processing boxes. This will allow us to have multiple back-end boxes handling traps, and to distribute load among those back end boxes. One key feature that we need is the ability to forward the traps to a specific box depending on the source address of the trap. Any suggestions for the best way to handle this? Among the things we've considered are: Using snmptrapd to accept the traps, and have it pass them off to a custom written perl handler script to rewrite the trap and send it to the proper processing box Using some sort of load balancing software running on a Linux box to handle this (having some difficulty finding many load balancing programs that will handle UDP) Using a Load Balancing Appliance (F5, etc) Using IPTables on a Linux box to route the SNMP traps with NATing We've currently implemented and are testing the last solution, with a Linux box with IPTables configured to receive the traps, and then depending on the source address of the trap, rewrite it with a destination nat (DNAT) so the packet gets sent to the proper server. For example: # Range: 10.0.0.0/19 Site: abc01 Destination: foo01 iptables -t nat -A PREROUTING -p udp --dport 162 -s 10.0.0.0/19 -j DNAT --to-destination 10.1.2.3 # Range: 10.0.33.0/21 Site: abc01 Destination: foo01 iptables -t nat -A PREROUTING -p udp --dport 162 -s 10.0.33.0/21 -j DNAT --to-destination 10.1.2.3 # Range: 10.1.0.0/16 Site: xyz01 Destination: bar01 iptables -t nat -A PREROUTING -p udp --dport 162 -s 10.1.0.0/16 -j DNAT --to-destination 10.3.2.1 This should work with excellent efficiency for basic trap routing, but it leaves us completely limited to what we can mach and filter on with IPTables, so we're concerned about flexibility for the future. Another feature that we'd really like, but isn't quite a "must have" is the ability to duplicate or mirror the UDP packets. Being able to take one incoming trap and route it to multiple destinations would be very useful. Has anyone tried any of the possible solutions above for SNMP traps (or Netflow, general UDP, etc) load balancing? Or can anyone think of any other alternatives to solve this?

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• Understanding packet flows over RVI

  - by choco-loo

  I'm trying to get a full grasp of firewall filters and how to apply them on a Juniper EX4200 switch - to be able to block ports, police traffic and shape traffic. The network architecture is as follows internet >-< vlan4000 >-< vlan43 vlan4000 is a public "routed" block (where all the IPs are routed to and the internet gw is) vlan43 is a vlan with public IPs with devices (servers) attached There are static routes and RVI's on the EX4200 to send all traffic via vlan4000's gateway to reach the internet. I've set up filters on both input and output of the respective RVI's and VLAN's - with simple counters, to measure traffic flow from a server inside of vlan43 and a server on the internet. Using a combination of iperf for UDP and TCP tests and fping for ICMP tests - I observed the following, icmp vlan43>internet internet>vlan43 unit4000-counter-in 0 0 unit4000-counter-out 0 0 unit43-counter-in 100 100 unit43-counter-out 0 0 vlan4000-counter-in 6 4 vlan4000-counter-out 107 104 vlan43-counter-in 101 100 vlan43-counter-out 100 100 tcp vlan43>internet internet>vlan43 unit4000-counter-in 0 0 unit4000-counter-out 0 0 unit43-counter-in 73535 38480 unit43-counter-out 0 0 vlan4000-counter-in 7 8 vlan4000-counter-out 73543 38489 vlan43-counter-in 73535 38481 vlan43-counter-out 38938 75880 udp vlan43>internet internet>vlan43 unit4000-counter-in 0 0 unit4000-counter-out 0 0 unit43-counter-in 81410 1 unit43-counter-out 0 0 vlan4000-counter-in 18 7 vlan4000-counter-out 81429 8 vlan43-counter-in 81411 1 vlan43-counter-out 1 85472 My key goals are to set up a few filters and policers, as there will be many more VLANs - that all need protecting from each other and the internet. Then globally limit/police all outbound traffic to the internet Block inbound ports to vlan43 (eg. 22) Limit outbound traffic from vlan43 (to the internet) Limit outbound traffic from vlan43 (to other vlans) Limit outbound traffic from vlan4000 (to the internet from all vlans) Route traffic from vlans via specific routing instances (FBF) The question What I want to understand is why there isn't ever any activity on unit4000 or vlan4000 inbound or outbound counter - is this because there isn't a device on this VLAN - and that the traffic is only traversing it? And with regards to the TCP test - why is there twice as many packets on unit43-counter-in, vlan4000-counter-out and vlan43-counter-in - is this counting both the inbound and outbound traffic?

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• "Hostile" network in the company - please comment on a security setup

  - by TomTom

  I have a little specific problem here that I want (need) to solve in a satisfactory way. My company has multiple (IPv4) networks that are controlled by our router sitting in the middle. Typical smaller shop setup. There is now one additional network that has an IP Range OUTSIDE of our control, connected to the internet with another router OUTSIDE of our control. Call it a project network that is part of another companies network and combined via VPN they set up. This means: They control the router that is used for this network and They can reconfigure things so that they can access the machines in this network. The network is physically split on our end through some VLAN capable switches as it covers three locations. At one end there is the router the other company controls. I Need / want to give the machines used in this network access to my company network. In fact, it may be good to make them part of my active directory domain. The people working on those machines are part of my company. BUT - I need to do so without compromising the security of my company network from outside influence. Any sort of router integration using the externally controlled router is out by this idea So, my idea is this: We accept the IPv4 address space and network topology in this network is not under our control. We seek alternatives to integrate those machines into our company network. The 2 concepts I came up with are: Use some sort of VPN - have the machines log into VPN. Thanks to them using modern windows, this could be transparent DirectAccess. This essentially treats the other IP space not different than any restaurant network a laptop of the company goes in. Alternatively - establish IPv6 routing to this ethernet segment. But - and this is a trick - block all IPv6 packets in the switch before they hit the third party controlled router, so that even IF they turn on IPv6 on that thing (not used now, but they could do it) they would get not a single packet. The switch can nicely do that by pulling all IPv6 traffic coming to that port into a separate VLAN (based on ethernet protocol type). Anyone sees a problem with using he switch to isolate the outer from IPv6? Any security hole? It is sad we have to treat this network as hostile - would be a lot easier - but the support personnel there is of "known dubious quality" and the legal side is clear - we can not fulfill our obligations when we integrate them into our company while they are under a jurisdiction we don't have a say in.

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• Latency issues over internet

  - by Stevo

  I have a Media Temple server running http://www.popsapp.com which I am having latency issues with. If I run ab -n 100 -c 10 http://www.popsapp.com/ from my local machine I get very bad stats e.g.: Connection Times (ms) min mean[+/-sd] median max Connect: 179 3375 2185.4 2837 12525 Processing: 0 505 693.3 229 4564 Waiting: 0 50 115.4 0 415 Total: 964 3880 2094.5 3159 12608 Whereas if I run it from a rackspace server I have I get this: Connection Times (ms) min mean[+/-sd] median max Connect: 75 76 3.3 75 84 Processing: 235 339 81.4 315 579 Waiting: 159 249 61.7 234 411 Total: 311 415 82.0 390 663 To me this looks like intermediate network issues, but I wouldn't have thought it could be this bad! Any ideas how I can improve it? Here's the trace route traceroute to www.popsapp.com (216.70.105.183), 64 hops max, 52 byte packets 1 192.168.2.1 (192.168.2.1) 3.738 ms 0.953 ms 1.418 ms 2 host-92-22-112-1.as13285.net (92.22.112.1) 27.409 ms 97.093 ms 78.858 ms 3 host-78-151-225-141.static.as13285.net (78.151.225.141) 61.830 ms 170.484 ms 113.288 ms 4 host-78-151-225-80.static.as13285.net (78.151.225.80) 101.513 ms host-78-151-225-22.static.as13285.net (78.151.225.22) 64.718 ms 47.309 ms 5 xe-11-1-0-rt001.sov.as13285.net (62.24.240.14) 98.381 ms 114.424 ms xe-11-1-0-rt001.the.as13285.net (62.24.240.6) 96.592 ms 6 host-78-144-1-59.as13285.net (78.144.1.59) 36.799 ms host-78-144-1-63.as13285.net (78.144.1.63) 178.426 ms host-78-144-1-61.as13285.net (78.144.1.61) 85.516 ms 7 xe-10-0-0-scr010.thn.as13285.net (78.144.0.224) 88.158 ms host-78-144-0-207.as13285.net (78.144.0.207) 35.132 ms host-78-144-0-153.as13285.net (78.144.0.153) 121.464 ms 8 limelight-pp-thn.as13285.net (78.144.3.6) 46.987 ms limelight-pp-sov.as13285.net (78.144.5.18) 108.025 ms 40.169 ms 9 tge11-1.fr4.lga.llnw.net (69.28.172.149) 109.603 ms ve6.fr4.lon.llnw.net (68.142.88.221) 121.681 ms 38.609 ms 10 tge11-1.fr4.lga.llnw.net (69.28.172.149) 111.981 ms 113.744 ms 111.711 ms 11 tge8-2.fr4.iad.llnw.net (69.28.189.34) 117.102 ms ve5.fr4.iad.llnw.net (69.28.171.214) 184.372 ms 146.178 ms 12 cr02-1-1.iad1.net2ez.com (65.97.48.254) 182.880 ms net2ez.tge2-2.fr4.iad.llnw.net (69.28.156.170) 150.489 ms 121.862 ms 13 65.97.50.26 (65.97.50.26) 184.620 ms cr02-1-1.iad1.net2ez.com (65.97.48.254) 156.136 ms 131.963 ms 14 65.97.50.26 (65.97.50.26) 124.899 ms 126.537 ms 123.322 ms 15 e1.4.as02.iad01.mtsvc.net (70.32.64.246) 134.647 ms 186.307 ms 211.059 ms 16 popsapp.com (216.70.105.183) 118.876 ms 113.189 ms vzx258.mediatemple.net (216.70.104.17) 131.012 ms Looks to me like there is significant delay across the limelight network. This would explain why the traceroute via my rackspace server doesn't suffer from the same delay as they will be using their own trunk.

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• Windows 2008 running as KVM guest networking issue

  - by Evolver

  I have a strange networking problem with Windows 2008 server R2, running as guest under KVM-Qemu host. Host is CentOS 6.3 x86_64. It's network settings: # cat /etc/sysconfig/network-scripts/ifcfg-br0 DEVICE=br0 BOOTPROTO=static BROADCAST=xx.xx.xx.63 IPADDR=xx.xx.xx.4 NETMASK=255.255.255.192 NETWORK=xx.xx.xx.0 ONBOOT=yes TYPE=Bridge # cat /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 HWADDR=xx:xx:xx:xx:xx:xx ONBOOT=yes BRIDGE=br0 IPV6INIT=yes IPV6_AUTOCONF=yes # cat /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=my.hostname GATEWAY=xx.xx.xx.1 # cat /etc/sysctl net.ipv4.ip_forward = 1 # tried to set it to 0 without any changes net.ipv4.conf.default.rp_filter = 1 # tried to set it to 0 without any changes net.ipv4.conf.default.accept_source_route = 0 # tried to set it to 1 without any changes kernel.sysrq = 0 kernel.core_uses_pid = 1 net.ipv4.tcp_syncookies = 1 net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 kernel.msgmnb = 65536 kernel.msgmax = 65536 kernel.shmmax = 68719476736 kernel.shmall = 4294967296 # route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface xx.xx.xx.0 0.0.0.0 255.255.255.192 U 0 0 0 br0 169.254.0.0 0.0.0.0 255.255.0.0 U 1004 0 0 br0 0.0.0.0 xx.xx.xx.1 0.0.0.0 UG 0 0 0 br0 Node IP is xx.xx.xx.4, guest IP is xx.xx.xx.24, both host and guest is in the same network (/26). There are several linux guest running fine on the node (centos, debian, ubuntu, arch), and even Windows 2003 x86 also running fine. But Win2008 does not. I wonder, what's the difference. From Win2008 guest I can ping nothing: neither gateway, nor any other IP, even they are in the same subnet. From outside I also cannot ping guest. Almost. If I ping it from another server in same subnet, it's barely pinging, losing more than 90% packets. Firewall on the guest is completely off. Tried to set up network manually as well as via DHCP without success (BTW, DHCP set up network settings correctly). I suspect that is a kind of routing problem, but I spent whole day and still cannot figure it out. I would be appreciate for any help.

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• Secure openVPN using IPTABLES

  - by bob franklin smith harriet

  Hey, I setup an openVPN server and it works ok. The next step is to secure it, I opted to use IPTABLES to only allow certain connections through but so far it is not working. I want to enable access to the network behind my openVPN server, and allow other services (web access), when iptables is disabaled or set to allow all this works fine, when using my following rules it does not. also note, I already configured openVPN itself to do what i want and it works fine, its only failing when iptables is started. Any help to tell me why this isnt working will appreciated here. These are the lines that I added in accordance with openVPN's recommendations, unfortunately testing these commands shows that they are requiered, they seem incredibly insecure though, any way to get around using them? # Allow TUN interface connections to OpenVPN server -A INPUT -i tun+ -j ACCEPT #allow TUN interface connections to be forwarded through other interfaces -A FORWARD -i tun+ -j ACCEPT # Allow TAP interface connections to OpenVPN server -A INPUT -i tap+ -j ACCEPT # Allow TAP interface connections to be forwarded through other interfaces -A FORWARD -i tap+ -j ACCEPT These are the new chains and commands i added to restrict access as much as possible unfortunately with these enabled, all that happens is the openVPN connection establishes fine, and then there is no access to the rest of the network behind the openVPN server note I am configuring the main iptables file and I am paranoid so all ports and ip addresses are altered, and -N etc appears before this so ignore that they dont appear. and i added some explanations of what i 'intended' these rules to do, so you dont waste time figuring out where i went wrong : 4 #accepts the vpn over port 1192 -A INPUT -p udp -m udp --dport 1192 -j ACCEPT -A INPUT -j INPUT-FIREWALL -A OUTPUT -j ACCEPT #packets that are to be forwarded from 10.10.1.0 network (all open vpn clients) to the internal network (192.168.5.0) jump to [sic]foward-firewall chain -A FORWARD -s 10.10.1.0/24 -d 192.168.5.0/24 -j FOWARD-FIREWALL #same as above, except for a different internal network -A FORWARD -s 10.10.1.0/24 -d 10.100.5.0/24 -j FOWARD-FIREWALL # reject any not from either of those two ranges -A FORWARD -j REJECT -A INPUT-FIREWALL -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT-FIREWALL -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT-FIREWALL -j REJECT -A FOWARD-FIREWALL -m state --state RELATED,ESTABLISHED -j ACCEPT #80 443 and 53 are accepted -A FOWARD-FIREWALL -m tcp -p tcp --dport 80 -j ACCEPT -A FOWARD-FIREWALL -m tcp -p tcp --dport 443 -j ACCEPT #192.168.5.150 = openVPN sever -A FOWARD-FIREWALL -m tcp -p tcp -d 192.168.5.150 --dport 53 -j ACCEPT -A FOWARD-FIREWALL -m udp -p udp -d 192.168.5.150 --dport 53 -j ACCEPT -A FOWARD-FIREWALL -j REJECT COMMIT now I wait :D

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• Too many TIME_WAIT state connections!

  - by Hamza

  I've been reading about this everywhere all day, and from what I've gathered, TIME_WAIT is a relatively harmless state. It's supposed to be harmless even when there's too many. But if they're jumping to the numbers I've been seeing for the past 24 hours, something is really wrong! [root@1 ~]# netstat -nat | awk '{print $6}' | sort | uniq -c | sort -n 1 established) 1 Foreign 12 CLOSE_WAIT 15 LISTEN 64 LAST_ACK 201 FIN_WAIT2 334 CLOSING 605 ESTABLISHED 816 SYN_RECV 981 FIN_WAIT1 26830 TIME_WAIT That number fluctuates from 20,000 to 30,000+ (so far, the maximum I've seen it go is 32,000). What worries me is that they're all different IP addresses from all sorts of random locations. Now this is supposed to be (or was supposed to be) a DDoS attack. I know this for a fact, but I won't go into the boring details. It started out as a DDoS and it did impact my server's performance for a couple minutes. After that, everything was back to normal. My server load is normal. My internet traffic is normal. No server resource is being abused. My sites load fine. I also have IPTABLES disabled. There's an odd issue with that too. Every time I enable the firewall/iptables, my server starts experiencing packet loss. Lots of it. About 50%-60% packets are lost. It happens within an hour or within a few hours of enabling the firewall. As soon as I disable it, ping responses from all locations I test them from start clearing up and get stable again. Very strange. The TIME_WAIT state connections have been fluctuating at those numbers since yesterday. For 24 hours now, I've had that, and although it hasn't impacted performance in any way, it's disturbing enough. My current tcp_fin_timeout value is 30 seconds, from the default 60 seconds. However, that seems to not help, at all. Any ideas, suggestions? Anything at all would be appreciated, really!

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• Why can I view my site over a 3G connection but not through my wifi?

  - by Jonathan

  So, I am sitting in my office with four computers on the same network and internet connection. Two of the computers can visit this particular website. Two of the computer get a message "Google Chrome could not find". I have tried FF and IE also with the same problem. I can view the site 90% of the time on two of the working computers although the site seems slow and sometimes I also get the same errors as the other two computers. I have flushed the DNS, reset the router, tested the site on other peoples computers with success. Is this likely to be a site issue, an ISP issue, a hosting issue? Any advice is greatly appreciated. Here is the ping from the working machine: C:\Users\Jon>ping www.balihaicruises.com Pinging www.balihaicruises.com [208.113.173.102] with 32 bytes of data: Reply from 208.113.173.102: bytes=32 time=331ms TTL=47 Reply from 208.113.173.102: bytes=32 time=327ms TTL=47 Reply from 208.113.173.102: bytes=32 time=326ms TTL=47 Reply from 208.113.173.102: bytes=32 time=329ms TTL=47 Ping statistics for 208.113.173.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 326ms, Maximum = 331ms, Average = 328ms Traceroute: Tracing route to www.balihaicruises.com [208.113.173.102] over a maximum of 30 hops: 1 1 ms 17 ms 3 ms 192.168.1.1 2 42 ms 37 ms 36 ms 180.254.224.1 3 39 ms 47 ms 40 ms 180.252.1.69 4 36 ms 616 ms 57 ms 61.94.115.221 5 84 ms 76 ms 80 ms 180.240.191.98 6 73 ms 80 ms 72 ms 180.240.191.97 7 157 ms 143 ms 116 ms 180.240.190.82 8 115 ms 113 ms 120 ms ae1-123.hkg11.ip4.tinet.net [183.182.80.93] 9 331 ms 332 ms 335 ms xe-3-2-1.was14.ip4.tinet.net [89.149.184.30] 10 327 ms 330 ms 331 ms internap-gw.ip4.tinet.net [77.67.69.254] 11 437 ms 415 ms 350 ms border10.pc2-bbnet2.wdc002.pnap.net [216.52.127.73] 12 322 ms 823 ms 398 ms dreamhost-2.border10.wdc002.pnap.net [216.52.125.74] 13 328 ms 336 ms 326 ms ip-208-113-156-4.dreamhost.com [208.113.156.4] 14 326 ms 328 ms 336 ms ip-208-113-156-14.dreamhost.com [208.113.156.14] 15 327 ms 331 ms 333 ms apache2-udder.crisp.dreamhost.com [208.113.173.102] And then for the machine that doesn't work: C:\Users\Microsoft>ping www.balihaicruises.com Ping request could not find host www.balihaicruises.com. Please check the name and try again. C:\Users\Microsoft>tracert www.balihaicruises.com Unable to resolve target system name www.balihaicruises.com.

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• Ubuntu: Multiple NICs, one used only for Wake-On-LAN

  - by jcwx86

  This is similar to some other questions, but I have a specific need which is not covered in the other questions. I have an Ubuntu server (11.10) with two NICs. One is built into the motherboard and the other is a PCI express card. I want to have my server connected to the internet via my NAT router and also have it able to wake from suspend using a Magic Packet (henceforth referred to as Wake-On-LAN, WOL). I can't do this with just one of the NICs because each has an issue - the built-in NIC will crash the system if it is placed under heavy load (typically downloading data), whilst the PCI express NIC will crash the system if it is used for WOL. I have spent some time investigating these individual problems, to no avail. My plan is thus: use the built-in NIC solely for WOL, and use the PCI express card for all other network communication except WOL. Since I send the WOL Magic Packet to a specific MAC address, there is no danger of hitting the wrong NIC, but there is a danger of using the built-in NIC for general network access, overloading it and crashing the system. Both NICs are wired to the same LAN with address space 192.168.0.0/24. The built-in ethernet card is set to have interface name eth1 and the PCI express card is eth0 in Ubuntu's udev persistent rules (so they stay the same upon reboot). I have been trying to set this up with the /etc/network/interfaces file. Here is where I am currently: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.168.0.3 netmask 255.255.255.0 network 192.168.0.0 broadcast 192.168.0.255 gateway 192.168.0.1 auto eth1 iface eth1 inet static address 192.168.0.254 netmask 255.255.255.0 I think by not specifying a gateway for eth1, I prevent it being used for outgoing requests. I don't mind if it can be reached on 192.168.0.254 on the LAN, i.e. via SSH -- it's IP is irrelevant to WOL, which is based on MAC addresses -- I just don't want it to be used to access internet resources. My kernel routing table (from route -n) is Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.0.1 0.0.0.0 UG 100 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 My question is this: Is this sufficient for what I want to achieve? My research has thrown up the idea of using static routing to specify that eth1 should only be used for WOL on the local network, but I'm not sure this is necessary. I have been monitoring the activity of the interfaces using iptraf and it seems like eth0 takes the vast majority of the packets, though I am not sure that this will be consistent based on my configuration. Given that if I mess up the configuration, my system will likely crash, it is important to me to have this set up correctly!

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• No Telnet login prompt when used over SSH tunnel

  - by SCO

  Hi there ! I have a device, let's call it d1, runnning a lightweight Linux. This device is NATed by my internet box/router, hence not reachable from the Internet. That device runs a telnet daemon on it, and only has root as user (no pwd). Its ip address is 192.168.0.126 on the private network. From the private network (let's say 192.168.0.x), I can do: telnet 192.168.0.126 Where 192.168.0.126 is the IP address in the private network. This works correctly. However, to allow administration, I'd need to access that device from outside of that private network. Hence, I created an SSH tunnel like this on d1 : ssh -R 4455:localhost:23 ussh@s1 s1 is a server somewhere in the private network (but this is for testing purposes only, it will endup somewhere in the Internet), running a standard Linux distro and on which I created a user called 'ussh'. s1 IP address is 192.168.0.48. When I 'telnet' with the following, let's say from c1, 192.168.0.19 : telnet -l root s1 4455 I get : Trying 192.168.0.48... Connected to 192.168.0.48. Escape character is '^]'. Connection closed by foreign host . The connection is closed after roughly 30 seconds, and I didn't log. I tried without the -l switch, without any success. I tried to 'telnet' with IP addresses instead of names to avoid reverse DNS issues (although I added to d1 /etc/hosts a line refering to s1 IP/name, just in case), no success. I tried on another port than 4455, no success. I gathered Wireshark logs from s1. I can see : s1 sends SSH data to c1, c1 ACK s1 performs an AAAA DNS request for c1, gets only the Authoritave nameservers. s1 performs an A DNS request, then gets c1's IP address s1 sends a SYN packet to c1, c1 replies with a RST/ACK s1 sends a SYN to c1, C1 RST/ACK (?) After 0.8 seconds, c1 sends a SYN to s1, s1 SYN/ACK and then c1 ACK s1 sends SSH content to d1, d1 sends an ACK back to s1 s1 retries AAAA and A DNS requests After 5 seconds, s1 retries a SYN to c1, once again it is RST/ACKed by c1. This is repeated 3 more times. The last five packets : d1 sends SSH content to s1, s1 sends ACK and FIN/ACK to c1, c1 replies with FIN/ACK, s1 sends ACK to c1. The connection seems to be closed by the telnet daemon after 22 seconds. AFAIK, there is no way to decode the SSH stream, so I'm really stuck here ... Any ideas ? Thank you !

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• Netcat file transfer problem

  - by thepurplepixel

  I have two custom scripts I just wrote to facilitate transferring files between my VPS and my home server. They are both written in bash (short & sweet): To send: #!/bin/bash SENDFILE=$1 PORT=$2 HOST='<my house>' HOSTIP=`host $HOST | grep "has address" | cut --delimiter=" " -f 4` echo Transferring file \"$SENDFILE\" to $HOST \($HOSTIP\). tar -c "$SENDFILE" | pv -c -N tar -i 0.5 | lzma -z -c -6 | pv -c -N lzma -i 0.5 | nc -q 1 $HOSTIP $PORT echo Done. To receive: #!/bin/bash SERVER='<myserver>' SERVERIP=`host $SERVER | grep "has address" | cut --delimiter=" " -f 4` PORT=$1 echo Receiving file from $SERVER \($SERVERIP\) on port $PORT. nc -l $PORT | pv -c -N netcat -i 0.5 | lzma -d -c | pv -c -N lzma -i 0.5 | tar -xf - echo Done. The problem is that, for a very quick second, I see something flash along the lines of "Connection Refused" (before pv overwrites it), and no file is ever transferred. The port is forwarded through my router, and nmap confirms it: ~$ sudo nmap -sU -PN -p55515 -v <my house> Starting Nmap 5.00 ( http://nmap.org ) at 2010-04-21 18:10 EDT NSE: Loaded 0 scripts for scanning. Initiating Parallel DNS resolution of 1 host. at 18:10 Completed Parallel DNS resolution of 1 host. at 18:10, 0.00s elapsed Initiating UDP Scan at 18:10 Scanning 74.13.25.94 [1 port] Completed UDP Scan at 18:10, 2.02s elapsed (1 total ports) Host 74.13.25.94 is up. Interesting ports on 74.13.25.94: PORT STATE SERVICE 55515/udp open|filtered unknown Read data files from: /usr/share/nmap Nmap done: 1 IP address (1 host up) scanned in 2.08 seconds Raw packets sent: 2 (56B) | Rcvd: 5 (260B) Also, running netcat normally doesn't work either: squircle@summit:~$ netcat <my house> 55515 <my house> [<my IP>] 55515 (?) : Connection refused Both boxes are Ubuntu Karmic (9.10). The receiver has no firewall, and outbound traffic on that port is allowed on the sender. I have no idea what to troubleshoot next. Any ideas? P.S.: Feel free to move this to SO/SF if you feel it would fit better there.

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• Apache proxy pass in nginx

  - by summerbulb

  I have the following configuration in Apache: RewriteEngine On #APP ProxyPass /abc/ http://remote.com/abc/ ProxyPassReverse /abc/ http://remote.com/abc/ #APP2 ProxyPass /efg/ http://remote.com/efg/ ProxyPassReverse /efg/ http://remote.com/efg/ I am trying to have the same configuration in nginx. After reading some links, this is what I have : server { listen 8081; server_name localhost; proxy_redirect http://localhost:8081/ http://remote.com/; location ^~/abc/ { proxy_set_header X-Forwarded-Host $host; proxy_set_header X-Forwarded-Server $host; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass http://remote.com/abc/; } location ^~/efg/ { proxy_set_header X-Forwarded-Host $host; proxy_set_header X-Forwarded-Server $host; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass http://remote.com/efg/; } } I already have the following configuration: server { listen 8080; server_name localhost; location / { root html; index index.html index.htm; } location ^~/myAPP { alias path/to/app; index main.html; } location ^~/myAPP/images { alias another/path/to/images autoindex on; } } The idea here is to overcome a same-origin-policy problem. The main pages are on localhost:8080 but we need ajax calls to http://remote.com/abc. Both domains are under my control. Using the above configuration, the ajax calls either don't reach the remote server or get cut off because of the cross origin. The above solution worked in Apache and isn't working in nginx, so I am assuming it's a configuration problem. I think there is an implicit question here: should I have two server declarations or should I somehow merge them into one? EDIT: Added some more information EDIT2: I've moved all the proxy_pass configuration into the main server declaration and changed all the ajax calls to go through port 8080. I am now getting a new error: 502 Connection reset by peer. Wireshark shows packets going out to http://remote.com with a bad IP header checksum.

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• iptables management tools for large scale environment

  - by womble

  The environment I'm operating in is a large-scale web hosting operation (several hundred servers under management, almost-all-public addressing, etc -- so anything that talks about managing ADSL links is unlikely to work well), and we're looking for something that will be comfortable managing both the core ruleset (around 12,000 entries in iptables at current count) plus the host-based rulesets we manage for customers. Our core router ruleset changes a few times a day, and the host-based rulesets would change maybe 50 times a month (across all the servers, so maybe one change per five servers per month). We're currently using filtergen (which is balls in general, and super-balls at our scale of operation), and I've used shorewall in the past at other jobs (which would be preferable to filtergen, but I figure there's got to be something out there that's better than that). The "musts" we've come up with for any replacement system are: Must generate a ruleset fairly quickly (a filtergen run on our ruleset takes 15-20 minutes; this is just insane) -- this is related to the next point: Must generate an iptables-restore style file and load that in one hit, not call iptables for every rule insert Must not take down the firewall for an extended period while the ruleset reloads (again, this is a consequence of the above point) Must support IPv6 (we aren't deploying anything new that isn't IPv6 compatible) Must be DFSG-free Must use plain-text configuration files (as we run everything through revision control, and using standard Unix text-manipulation tools are our SOP) Must support both RedHat and Debian (packaged preferred, but at the very least mustn't be overtly hostile to either distro's standards) Must support the ability to run arbitrary iptables commands to support features that aren't part of the system's "native language" Anything that doesn't meet all these criteria will not be considered. The following are our "nice to haves": Should support config file "fragments" (that is, you can drop a pile of files in a directory and say to the firewall "include everything in this directory in the ruleset"; we use configuration management extensively and would like to use this feature to provide service-specific rules automatically) Should support raw tables Should allow you to specify particular ICMP in both incoming packets and REJECT rules Should gracefully support hostnames that resolve to more than one IP address (we've been caught by this one a few times with filtergen; it's a rather royal pain in the butt) The more optional/weird iptables features that the tool supports (either natively or via existing or easily-writable plugins) the better. We use strange features of iptables now and then, and the more of those that "just work", the better for everyone.

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• Routing RFC1918 addresses through dd-wrt via a switch

  - by espenfjo

  I am a bit stuck with an experiment of mine. I have a network looking somewhat like this. | Internet | | ---- |Switch| ---- | | Server w/pub IP | DD-WRT router 192.168.1.1 | | RFC1918 clients 192.168.1.0/24 What I want is for the RFC1918 clients to speak directly with each others. On the server with the public IP I have this route: 192.168.1.0/24 dev eth0 scope link and can see that packets are infact reaching the dd-wrt router for 192.168.1.1, even though if I get no answer. Trying to reach one of the RFC1918 clients from the public IP server will get no result, as the dd-wrt router is not announcing that network on to its external interface (arp who-has 192.168.1.107 tell xxx.xxx.xxx.xxx, but no answer). The router being an WLAN dd-wrt router has of course a load of routes, VLANs and interfaces: xxx.xxx.xxx.1 dev vlan2 scope link 192.168.1.0/24 dev br0 proto kernel scope link src 192.168.1.1 192.168.1.0/24 dev eth1 proto kernel scope link src 192.168.1.244 84.215.64.0/18 dev vlan2 proto kernel scope link src xxx.xxx.xxx.xxx 169.254.0.0/16 dev br0 proto kernel scope link src 169.254.255.1 127.0.0.0/8 dev lo scope link 0.0.0.0 via xxx.xxx.xxx.1 dev vlan2 xxx.xxx.xxx.xxx being the public IP, and xxx.xxx.xxx.1 being the default route for the public IP. I am not sure where to continue with this. I would recon that I both need routing on the dd-wrt router, as well as some iptables magic? Why do something this complex? Why not ;) Also, do not mind that "Internet" can get RFC1918 traffic, it wont go outside of the walls. EDIT 1: Following the tip from stew I do indeed get the correct ARP flowing. And adding an iptables rule for allowing traffic from that specific public IPd machine I get traffic between the systems! Oddly enough though, the speed I get from Server w/pub IP - RFC1918 clients are the same as if the traffic were routed out onto the Internet and back. Edit 2: Ok, disconnecting the external Internet connection will still give the same, crappy transfer speed. So it has to be something else. Edit 3: Ok, I guess there are other reasons for this crappy speed. Case closed. :)

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• Airport Express chokes Wi-Fi for a few seconds, several times per hour. Any idea why?

  - by user13727

  I'm using a MacBookPro connected to an AiportExpress' Wi-FI network. Every once in a while, the Wi-Fi will choke up and either drop some packets, or lag horribly for several seconds. I'm losing hair over this because every time I chat on Skype, the call hangs randomly due to this problem. Any idea what's wrong? Some more details: two networks are set up: 2.4Ghz and 5Ghz, and the issue happens on both the network uses WPA2 Personal for security the Airport is in the same room with my computer the Airport is fairly new, bought this summer, model number off the back: A1392 tried connecting to a neighbours wifi to see if it's a problem with my computer, or interference. It's not, it doesn't happen on their network. tried resetting it several times tried changing channels manually Ping results are below, so you can see what I'm talking about. EDIT: 10.0.1.1 is the Airport's IP 64 bytes from 10.0.1.1: icmp_seq=1795 ttl=255 time=0.813 ms 64 bytes from 10.0.1.1: icmp_seq=1796 ttl=255 time=3.335 ms 64 bytes from 10.0.1.1: icmp_seq=1797 ttl=255 time=3.403 ms 64 bytes from 10.0.1.1: icmp_seq=1798 ttl=255 time=3.414 ms 64 bytes from 10.0.1.1: icmp_seq=1799 ttl=255 time=3.227 ms 64 bytes from 10.0.1.1: icmp_seq=1800 ttl=255 time=3.274 ms 64 bytes from 10.0.1.1: icmp_seq=1801 ttl=255 time=3.253 ms 64 bytes from 10.0.1.1: icmp_seq=1802 ttl=255 time=3.292 ms >>>> choke starts <<< 64 bytes from 10.0.1.1: icmp_seq=1803 ttl=255 time=53.977 ms 64 bytes from 10.0.1.1: icmp_seq=1804 ttl=255 time=35.049 ms 64 bytes from 10.0.1.1: icmp_seq=1805 ttl=255 time=19.820 ms >>>> choke ends <<< 64 bytes from 10.0.1.1: icmp_seq=1806 ttl=255 time=0.716 ms 64 bytes from 10.0.1.1: icmp_seq=1807 ttl=255 time=0.705 ms 64 bytes from 10.0.1.1: icmp_seq=1808 ttl=255 time=0.919 ms 64 bytes from 10.0.1.1: icmp_seq=1809 ttl=255 time=0.659 ms 64 bytes from 10.0.1.1: icmp_seq=1810 ttl=255 time=0.877 ms 64 bytes from 10.0.1.1: icmp_seq=1811 ttl=255 time=0.679 ms 64 bytes from 10.0.1.1: icmp_seq=1812 ttl=255 time=0.854 ms 64 bytes from 10.0.1.1: icmp_seq=1813 ttl=255 time=0.644 ms 64 bytes from 10.0.1.1: icmp_seq=1814 ttl=255 time=3.779 ms ... time passes .. 64 bytes from 10.0.1.1: icmp_seq=1599 ttl=255 time=0.674 ms 64 bytes from 10.0.1.1: icmp_seq=1600 ttl=255 time=0.930 ms 64 bytes from 10.0.1.1: icmp_seq=1601 ttl=255 time=0.665 ms 64 bytes from 10.0.1.1: icmp_seq=1602 ttl=255 time=1.085 ms Request timeout for icmp_seq 1603 Request timeout for icmp_seq 1604 64 bytes from 10.0.1.1: icmp_seq=1605 ttl=255 time=104.969 ms 64 bytes from 10.0.1.1: icmp_seq=1606 ttl=255 time=11.521 ms 64 bytes from 10.0.1.1: icmp_seq=1607 ttl=255 time=0.926 ms 64 bytes from 10.0.1.1: icmp_seq=1608 ttl=255 time=0.993 ms 64 bytes from 10.0.1.1: icmp_seq=1609 ttl=255 time=0.745 ms And the Signal-Noise ratio:

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• iptables : how to correctly allow incoming and outgoing traffic for certain ports?

  - by Rubytastic

  Im trying to get incoming and outgoing traffic to be enabled on specific ports, because I block everything at the end of the iptables rules. INPUT and FORWARD reject. What would be the appropiate way to open certain ports for all traffic incoming and outgoing? From docs I found below but one has to really define both lines? iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT I try to open ports for xmpp service and some other deamons running on server. Rules: *filter # Allow all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0 -A INPUT -i lo -j ACCEPT -A INPUT -d 127.0.0.0/8 -j REJECT # Accept all established inbound connections -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # Allow all outbound traffic - you can modify this to only allow certain traffic -A OUTPUT -j ACCEPT # Allow HTTP # Prevent DDOS attacks (http://blog.bodhizazen.net/linux/prevent-dos-with-iptables/) # Disallow HTTPS -A INPUT -p tcp --dport 80 -m state --state NEW -m limit --limit 50/minute --limit-burst 200 -j ACCEPT -A INPUT -m state --state RELATED,ESTABLISHED -m limit --limit 50/second --limit-burst 50 -j ACCEPT -A INPUT -p tcp --dport 443 -j DROP # Allow SSH connections # The -dport number should be the same port number you set in sshd_config -A INPUT -p tcp -s <myip> --dport ssh -j ACCEPT -A INPUT -p tcp -s <myip> --dport 5984 -j ACCEPT -A INPUT -p tcp --dport ssh -j REJECT # Attempt to block portscans # Anyone who tried to portscan us is locked out for an entire day. -A INPUT -m recent --name portscan --rcheck --seconds 86400 -j DROP -A FORWARD -m recent --name portscan --rcheck --seconds 86400 -j DROP # Once the day has passed, remove them from the portscan list -A INPUT -m recent --name portscan --remove -A FORWARD -m recent --name portscan --remove # These rules add scanners to the portscan list, and log the attempt. -A INPUT -p tcp -m tcp --dport 139 -m recent --name portscan --set -j LOG --log-prefix "Portscan:" -A INPUT -p tcp -m tcp --dport 139 -m recent --name portscan --set -j DROP -A FORWARD -p tcp -m tcp --dport 139 -m recent --name portscan --set -j LOG --log-prefix "Portscan:" -A FORWARD -p tcp -m tcp --dport 139 -m recent --name portscan --set -j DROP # Stop smurf attacks -A INPUT -p icmp -m icmp --icmp-type address-mask-request -j DROP -A INPUT -p icmp -m icmp --icmp-type timestamp-request -j DROP -A INPUT -p icmp -m icmp -j DROP # Drop excessive RST packets to avoid smurf attacks -A INPUT -p tcp -m tcp --tcp-flags RST RST -m limit --limit 2/second --limit-burst 2 -j ACCEPT # Don't allow pings through -A INPUT -p icmp -m icmp --icmp-type 8 -j DROP # Log iptables denied calls -A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7 # Reject all other inbound - default deny unless explicitly allowed policy -A INPUT -j REJECT -A FORWARD -j REJECT COMMIT

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• unable to access a NAT'ed IP via a VPN on Windows 7

  - by crmpicco

  I connect to a range of servers hosted by one provider via a VPN. I can connect to the VPN fine, however when I then go and try and connect to the server(s) it fails. A NAT'ed IP address that has worked up until today, has stopped working either via SSH/SFTP. As you can see below, if I try and ping the IP then it responds with Destination host unreachable, but, for some reason it says the reply is from 192.168.0.8? If it enter this IP address in my browser, I get nothing. Where is this IP coming from and is there any good reason why I cannot access the IP I am trying to ping? C:\Users\crmpicco>ping 172.26.100.x Pinging 172.26.100.x with 32 bytes of data: Reply from 192.168.0.8: Destination host unreachable. Reply from 192.168.0.8: Destination host unreachable. Reply from 192.168.0.8: Destination host unreachable. Reply from 192.168.0.8: Destination host unreachable. Ping statistics for 172.26.100.x: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), I have the VPN remote host address of 80.75.67.x, which shows me as being connected. But i'm unsure if there is a config issue at the server side or my end that has caused this issue? I have had some recent Win7 (automatic) updates, but it's hard to tell if that's caused this problem. This is my output from arp: C:\Users\cmorton>arp -a Interface: 192.168.0.8 --- 0xe Internet Address Physical Address Type 192.168.0.1 00-18-4d-b9-68-5e dynami 192.168.0.6 00-f4-b9-68-0c-9a dynami 192.168.0.7 08-00-27-f2-9f-d6 dynami 192.168.0.255 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 239.255.255.250 01-00-5e-7f-ff-fa static 255.255.255.255 ff-ff-ff-ff-ff-ff static Interface: 192.168.56.1 --- 0x15 Internet Address Physical Address Type 192.168.56.255 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 255.255.255.255 ff-ff-ff-ff-ff-ff static

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• Switch flooding when bonding interfaces in Linux

  - by John Philips

  +--------+ | Host A | +----+---+ | eth0 (AA:AA:AA:AA:AA:AA) | | +----+-----+ | Switch 1 | (layer2/3) +----+-----+ | +----+-----+ | Switch 2 | +----+-----+ | +----------+----------+ +-------------------------+ Switch 3 +-------------------------+ | +----+-----------+----+ | | | | | | | | | | eth0 (B0:B0:B0:B0:B0:B0) | | eth4 (B4:B4:B4:B4:B4:B4) | | +----+-----------+----+ | | | Host B | | | +----+-----------+----+ | | eth1 (B1:B1:B1:B1:B1:B1) | | eth5 (B5:B5:B5:B5:B5:B5) | | | | | | | | | +------------------------------+ +------------------------------+ Topology overview Host A has a single NIC. Host B has four NICs which are bonded using the balance-alb mode. Both hosts run RHEL 6.0, and both are on the same IPv4 subnet. Traffic analysis Host A is sending data to Host B using some SQL database application. Traffic from Host A to Host B: The source int/MAC is eth0/AA:AA:AA:AA:AA:AA, the destination int/MAC is eth5/B5:B5:B5:B5:B5:B5. Traffic from Host B to Host A: The source int/MAC is eth0/B0:B0:B0:B0:B0:B0, the destination int/MAC is eth0/AA:AA:AA:AA:AA:AA. Once the TCP connection has been established, Host B sends no further frames out eth5. The MAC address of eth5 expires from the bridge tables of both Switch 1 & Switch 2. Switch 1 continues to receive frames from Host A which are destined for B5:B5:B5:B5:B5:B5. Because Switch 1 and Switch 2 no longer have bridge table entries for B5:B5:B5:B5:B5:B5, they flood the frames out all ports on the same VLAN (except for the one it came in on, of course). Reproduce If you ping Host B from a workstation which is connected to either Switch 1 or 2, B5:B5:B5:B5:B5:B5 re-enters the bridge tables and the flooding stops. After five minutes (the default bridge table timeout), flooding resumes. Question It is clear that on Host B, frames arrive on eth5 and exit out eth0. This seems ok as that's what the Linux bonding algorithm is designed to do - balance incoming and outgoing traffic. But since the switch stops receiving frames with the source MAC of eth5, it gets timed out of the bridge table, resulting in flooding. Is this normal? Why aren't any more frames originating from eth5? Is it because there is simply no other traffic going on (the only connection is a single large data transfer from Host A)? I've researched this for a long time and haven't found an answer. Documentation states that no switch changes are necessary when using mode 6 of the Linux interface bonding (balance-alb). Is this behavior occurring because Host B doesn't send any further packets out of eth5, whereas in normal circumstances it's expected that it would? One solution is to setup a cron job which pings Host B to keep the bridge table entries from timing out, but that seems like a dirty hack.

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• My network drive disappears from Mac OS Finder

  - by Mariusz

  I have recently bought a Netgear WNDR3800 router to use it in my home network. But just the same day I installed it, I noticed a strange behaviour of Finder and iTunes. Let me explain it further. There is a Synology DS111 NAS attached to that router and two Macs with Mac OS X Lion. One of them is connected by a cable and the second one wirelessly. Before I changed my router to the new one I mentioned above, Finder always used to display my NAS on its sidebar. So I could just click its network name to access shared folders existing on it. But after I installed WNDR3800, I can no longer access the NAS that way. It is no longer displayed. I always have to mount it manually by typing its IP address using the Finder's 'connect to server' option. The same NAS supports TimeMachine backups and has an inbuilt DLNA server. And the same situation here. I can't perform a backup because my NAS is no longer accessible in TimeMachine preferences. iTunes does not display it as well (as a multimedia server) even though it used to before I installed that router. What's important, everything works fine for a couple of minutes after I restart the router or the NAS. Or even when I change the NAS's IP address it becomes accessible again in Finder, TimeMachine and iTunes, but only for some time. Both the Mac computers I mentioned behave the same way. And all those issues have been taking place sice I installed that new router. Before I did that, everything had worked fine. My old router was Netgear WGR614v10. Would you be so kind to tell me what you think could possibly be the reason of that behaviour? What settings of the router should I look closer at? I'm not a network specialist, but is it possible that some network packets are blocked for some reason? I will be grateful for any clues you give me. Thank you.

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• how to setup kismet.conf on Ubuntu

  - by Registered User

  I installed Kismet on my Ubuntu 10.04 machine as apt-get install kismet every thing seems to work fine. but when I launch it I see following error kismet Launching kismet_server: //usr/bin/kismet_server Suid priv-dropping disabled. This may not be secure. No specific sources given to be enabled, all will be enabled. Non-RFMon VAPs will be destroyed on multi-vap interfaces (ie, madwifi-ng) Enabling channel hopping. Enabling channel splitting. NOTICE: Disabling channel hopping, no enabled sources are able to change channel. Source 0 (addme): Opening none source interface none... FATAL: Please configure at least one packet source. Kismet will not function if no packet sources are defined in kismet.conf or on the command line. Please read the README for more information about configuring Kismet. Kismet exiting. Done. I followed this guide http://www.ubuntugeek.com/kismet-an-802-11-wireless-network-detector-sniffer-and-intrusion-detection-system.html#more-1776 how ever in kismet.conf I am not clear with following line source=none,none,addme as to what should I change this to. lspci -vnn shows 0c:00.0 Network controller [0280]: Broadcom Corporation BCM4312 802.11b/g [14e4:4315] (rev 01) Subsystem: Dell Device [1028:000c] Flags: bus master, fast devsel, latency 0, IRQ 17 Memory at f69fc000 (64-bit, non-prefetchable) [size=16K] Capabilities: [40] Power Management version 3 Capabilities: [58] Vendor Specific Information <?> Capabilities: [e8] Message Signalled Interrupts: Mask- 64bit+ Queue=0/0 Enable- Capabilities: [d0] Express Endpoint, MSI 00 Capabilities: [100] Advanced Error Reporting <?> Capabilities: [13c] Virtual Channel <?> Capabilities: [160] Device Serial Number Capabilities: [16c] Power Budgeting <?> Kernel driver in use: wl Kernel modules: wl, ssb and iwconfig shows lo no wireless extensions. eth0 no wireless extensions. eth1 IEEE 802.11bg ESSID:"WIKUCD" Mode:Managed Frequency:2.462 GHz Access Point: <00:43:92:21:H5:09> Bit Rate=11 Mb/s Tx-Power:24 dBm Retry min limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Managementmode:All packets received Link Quality=1/5 Signal level=-81 dBm Noise level=-90 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:169 Invalid misc:0 Missed beacon:0 So what should I be putting in place of source=none,none,addme with output I mentioned above ?

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