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• Windows Server 2008 network speed slow, Xen 3.4.3 HVM ISO

  - by Elliot.Bradshaw

  I've setup a VM running Windows Server 2008 on a host node running Xen 3.4.3-5 and the following kernel: 2.6.18-308.1.1.el5xen #1 SMP Wed Mar 7 05:38:01 EST 2012 i686 i686 i386 GNU/Linux The network speed on the VM is very slow--using the online speed tests I can only get it up to 8-9mbps. The line is 100mbps burstable and the host node has no problem achieving those speeds. If it setup a VM running CentOS, it too has no problems achieving those speeds. I've done some pretty exhaustive troubleshooting, but nothing has helped: New VM installations of Win2k8 do have the same network problem. Upgrading to most recent kernel-xen did not help (2.6.18-308.1.1.el5xen). Upgrading from xen 3.4.0 to xen 3.4.3-5 did not help. Disabling Windows firewall, etc did not help. Changing network card device config from auto negotiation to manually be 100mbps full duplex did not help. Changing the network receive buffer packet size did not help (tried all combos from 64k to 8k). At this point I'm pretty much out of ideas--any help would be appreciated!

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• Wireless router blocking some sites while using ethernet is fine

  - by Micke

  I'm using Windows 7 and my router is a wireless Apple Airport Express that is approximately two years old. Suddenly I can't access some sites (for example www.sthlm.friskissvettis.se, or www.vegetarian-shoes.co.uk, some streamed tv-shows on svtplay.se, and a number of other random sites) when connecting to internet with my router. It worked good until recently and I'm fairly sure this problem emerged when my ISP upgraded from 10/10mbit to 100/10mbit speed. Most other sites like facebook and google works fine. When using my network cable to connect to internet everything works fine and I can access these sites. Firmware is current and I've tried reseting the router to factory defaults. Tried different browsers, and I can't ping the "blocked" sites either. Tracert www.sthlm.friskissvettis.se starts with 10.0.0.1 and continues through a number of long addresses until it says timeout. The last working address before timeout was sth-tcy-ipcore01-ge-0-2-0.neq.dgcsystems.net [83.241.252.13], if it matters. Tracert www.vegetarian-shoes.co.uk also eventually gives me a timeout. When the network cable is plugged in, I still get timeout on tracert www.sthlm.friskissvettis.se even though I can access the site in Chrome. Weird. www.vegetarian-shoes.co.uk doesn't give me a tracert timeout when the cable is plugged in, and I can access the site as usual. I've tried changing DNS servers to use opendns servers instead, but to no use. I've tried pinging these two sites with a lower MTU packet size (with this method: http://www.richard-slater.co.uk/archives/2009/10/23/change-your-mtu-under-vista-or-windows-7/), but still can't access them through ping... I don't know what to do anymore.... any suggestions???

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• Determine the time difference between two linux servers

  - by Paul

  I am troubleshooting a latency network issue on a network. It is probably a nic or cabling issue, but while I was going through the process of figuring it out, I was looking at the timings of a ping packet leaving a network card and arriving at another server. Both linux. So I have tcpdump running on both, and I issue a ping from one to the other, and back again, and looking at the timing differences might have shed light on where the latency is coming from. It is an academic exercise now, as I need to eliminate some more fundamental causes, but I was curious as to how this could be achieved. Given that ntpd is installed and running on two servers, how can I confirm the current time discrepency between the two servers, to whatever level of accuracy is possible - given that we are talking about latency on a local lan, which is ideally a millisecond or so. NTP itself is accurate to a couple of ms under good conditions, and as both servers are in the same environment, they should (presumably) achieve a similar level of accuracy, and so should have a time discrepency between them of a only few ms - but how can I check this?

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• can't Remote desktop to windows XP, blaming the server side

  - by Jin

  After rebooting my work PC (windows XP sp3) this Wednesday (thank to Microsoft Tuesday), I found that I can't remote desktop to my work PC from home (with VPN to company). I have been remote-desktop to work for years and I am really surprised since connectivity is not the problem, so I brought up wireshark to sniff the packets. I can see after TCP handshake, client sent X.224 Connection Request 03 00 00 13 0e e0 00 00 00 00 00 01 00 08 00 03 00 00 00 server sent X.224 Connection Confirm. 03 00 00 0b 06 d0 00 00 12 34 00 According to "MS-RDPBCGR", the official spec on RDP, the server should include Negotiation Response in the "Connection Confirm" message but it didn't. It's empty. I googled a lot but didn't find any clue on why server did that. By the way, I used the same remote desktop client and can connect to other windows XP PC. Here are a couple of pieces of information that may help to give a clue: Since TCP handshake (server port being 3389), I believe the svchost service is actually running. going to control panel -- system window, --- "Remote" tab, the remote desktop is indeeded checked and it states that my username is allowed. according to the packet capture, client didn't even get a chance to tell server what user was trying to logon. Yes, the progress bar showed up a few seconds and then it went back to the "Remote desktop Connection" window again. Searched "windowsupdate.log", didn't find any appearance of the word "remote".

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• Fast Ethernet module for Cisco 2620

  - by Kenny Rasschaert

  I have a Cisco 2620 Router. It comes with one fast ethernet port built in (circled in red), and one old AUI ethernet module is installed (circled in blue). I figure I can put a transceiver on the AUI interface to get a second RJ45 connector. What I'd really like to have is a second fast ethernet connector. The ideal candidate to achieve this would be the NM-1FE-TX module. Cisco claims on their website that this module is not suitable for the Cisco 2620 and Cisco 2620XM. It says so in "Table 2 Physical Limitation of Serial Modules per Chassis". Indeed, this module was designed for the 3600 series of routers. I've seen claims on the internet, however, of people having this module on a 2620XM, and it being fully functional. This claim gains some credibility because of the fact that in Cisco's own Packet Tracer software, you can install this module on the 2620XM router. I'm looking for a definitive answer. Will this module work on a Cisco 2620? Is there perhaps another way to get a second fast ethernet port on this device?

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• Overriding routes on Openvpn client, iproute, iptables2

  - by sarvavijJana

  I am looking for some way to route packets based on its destination ports switching regular internet connection and established openvpn tunnel. This is my configuration OpenVPN server ( I have no control over it ) OpenVPN client running ubuntu wlan0 192.168.1.111 - internet connected if Several routes applied on connection to openvpn from server: /sbin/route add -net 207.126.92.3 netmask 255.255.255.255 gw 192.168.1.1 /sbin/route add -net 0.0.0.0 netmask 128.0.0.0 gw 5.5.0.1 /sbin/route add -net 128.0.0.0 netmask 128.0.0.0 gw 5.5.0.1 And I need to route packets regarding it's destination ports for ex: 80,443 into vpn everything else directly to isp connection 192.168.1.1 What i have used during my attempts: iptables -A OUTPUT -t mangle -p tcp -m multiport ! --dports 80,443 -j MARK --set-xmark 0x1/0xffffffff ip rule add fwmark 0x1 table 100 ip route add default via 192.168.1.1 table 100 I was trying to apply this settings using up/down options of openvpn client configuration All my attempts reduced to successful packet delivery and response only via vpn tunnel. Packets routed bypassing vpn i have used some SNAT to gain proper src address iptables -A POSTROUTING -t nat -o $IF -p tcp -m multiport --dports 80,443 -j SNAT --to $IF_IP failed in SYN-ACK like 0 0,1 0,1: "70","192.168.1.111","X.X.X.X","TCP","34314 > 81 [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=18664016 TSER=0 WS=7" "71","X.X.X.X","192.168.1.111","TCP","81 > 34314 [SYN, ACK] Seq=0 Ack=1 Win=5792 Len=0 MSS=1428 TSV=531584430 TSER=18654692 WS=5" "72","X.X.X.X","192.168.1.111","TCP","81 > 34314 [SYN, ACK] Seq=0 Ack=1 Win=5792 Len=0 MSS=1428 TSV=531584779 TSER=18654692 WS=5" "73","192.168.1.111","X.X.X.X","TCP","34343 > 81 [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=18673732 TSER=0 WS=7" I hope someone has already overcome such a situation or probably knows better approach to fulfill requirements. Please kindly give me a good advice or working solution.

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• Difference between "traceroute" and "traceroute -U"

  - by AndiDog

  The manpage of traceroute says that the "-U" parameter (UDP probing) is the default, but I'm getting different results every time. With "-U": traceroute -U www.univ-paris1.fr traceroute to www.univ-paris1.fr (193.55.96.121), 30 hops max, 60 byte packets [...] 13 rap-vl165-te3-2-jussieu-rtr-021.noc.renater.fr (193.51.181.101) 59.445 ms 56.924 ms 56.651 ms [...] 18 * paris1web.univ-paris1.fr (193.55.96.121) 23.797 ms 23.603 ms but the normal traceroute gives me another result (never reaches the final node) - it's either "!X" or just exits after the maximum of 30 hops: traceroute www.univ-paris1.fr traceroute to www.univ-paris1.fr (193.55.96.121), 30 hops max, 60 byte packets [...] 11 te1-1-paris1-rtr-021.noc.renater.fr (193.51.189.38) 28.147 ms 28.250 ms 28.538 ms [... non-responding nodes ...] 28 site-1.03-jussieu.rap.prd.fr (195.221.126.58) 85.941 ms !X * * Note: I tried this very often and always get the same results. The path in my local network is always the same. So what does the "-U" parameter actually change here? I'm especially interested what the reason for "!X" could be (communication administratively prohibited). EDIT: If that helps, paris-traceroute gives me the following for the last hop: 14 P(1, 6) site-1.03-jussieu.rap.prd.fr (195.221.126.58) 34.938 ms !5 !T2 which means that node discards the packet with TTL=2 and returns an unknown message (not "destination unreachable" or the like).

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• Why can't I route to some sites from my MacBook Pro that I can see from my iPad?

  - by Robert Atkins

  I am on M1 Cable (residential) broadband in Singapore. I have an intermittent problem routing to some sites from my MacBook Pro—often Google-related sites (arduino.googlecode.com and ajax.googleapis.com right now, but sometimes even gmail.com.) This prevents StackExchange chat from working, for instance. Funny thing is, my iPad can route to those sites and they're on the same wireless network! I can ping the sites, but not traceroute to them which I find odd. That I can get through via the iPad implies the problem is with the MBP. In any case, calling M1 support is... not helpful. I get the same behaviour when I bypass the Airport Express entirely and plug the MBP directly into the cable modem. Can anybody explain a) how this is even possible and b) how to fix it? mella:~ ratkins$ ping ajax.googleapis.com PING googleapis.l.google.com (209.85.132.95): 56 data bytes 64 bytes from 209.85.132.95: icmp_seq=0 ttl=50 time=11.488 ms 64 bytes from 209.85.132.95: icmp_seq=1 ttl=53 time=13.012 ms 64 bytes from 209.85.132.95: icmp_seq=2 ttl=53 time=13.048 ms ^C --- googleapis.l.google.com ping statistics --- 3 packets transmitted, 3 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 11.488/12.516/13.048/0.727 ms mella:~ ratkins$ traceroute ajax.googleapis.com traceroute to googleapis.l.google.com (209.85.132.95), 64 hops max, 52 byte packets traceroute: sendto: No route to host 1 traceroute: wrote googleapis.l.google.com 52 chars, ret=-1 *traceroute: sendto: No route to host traceroute: wrote googleapis.l.google.com 52 chars, ret=-1 ^C mella:~ ratkins$ The traceroute from the iPad goes (and I'm copying this by hand): 10.0.1.1 119.56.34.1 172.20.8.222 172.31.253.11 202.65.245.1 202.65.245.142 209.85.243.156 72.14.233.145 209.85.132.82 From the MBP, I can't traceroute to any of the IPs from 172.20.8.222 onwards. [For extra flavour, not being able to access the above appears to stop me logging in to Server Fault via OpenID and formatting the above traceroutes correctly. Anyone with sufficient rep here to do so, I'd be much obliged.]

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• Redundant OpenVPN connections with advanced Linux routing over an unreliable network

  - by konrad

  I am currently living in a country that blocks many websites and has unreliable network connections to the outside world. I have two OpenVPN endpoints (say: vpn1 and vpn2) on Linux servers that I use to circumvent the firewall. I have full access to these servers. This works quite well, except for the high package loss on my VPN connections. This packet loss varies between 1% and 30% depending on time and seems to have a low correlation, most of the time it seems random. I am thinking about setting up a home router (also on Linux) that maintains OpenVPN connections to both endpoints and sends all packets twice, to both endpoints. vpn2 would send all packets from home to vpn1. Return trafic would be send both directly from vpn1 to home, and also through vpn2. +------------+ | home | +------------+ | | | OpenVPN | | links | | | ~~~~~~~~~~~~~~~~~~ unreliable connection | | +----------+ +----------+ | vpn1 |---| vpn2 | +----------+ +----------+ | +------------+ | HTTP proxy | +------------+ | (internet) For clarity: all packets between home and the HTTP proxy will be duplicated and sent over different paths, to increase the chances one of them will arrive. If both arrive, the first second one can be silently discarded. Bandwidth usage is not an issue, both on the home side and endpoint side. vpn1 and vpn2 are close to each other (3ms ping) and have a reliable connection. Any pointers on how this could be achieved using the advanced routing policies available in Linux?

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• ProCurve 1800 switch issue

  - by user98651

  I recently deployed ProCurve 1800-24G switches in place of some older ProCurve 2424M switches in my network. However, I'm having a serious problem with the switch connected to the router. It seems, every night when our Windows 2008 R2 server (off site) runs a backup to a iSCSI target (on site) [facilitated through a PPTP tunnel] the LAN loses connectivity with the router. To clarify, there is only one router which is connected to the switch affected by this problem. The only way to resolve the issue is to either reboot the router or pull the ethernet cable that goes to the router and plug it back in. During the outage, clients cannot receive DHCP requests, DNS requests, ping, or do anything else with the router in this state. Now, neither the switch or router are configured extensively and the issue only seems to have surfaced with the new switch in place. I have tried a number of things including replacing cables, rebooting and checking the switch configuration (it is literally as basic as you can get at this point-- flat LAN, no trunking). Interestingly, the router shows (accessed externally) no changes in configuration or status during this state but similarly cannot ping or access other hosts on the network. This issue occurs in different stages of backup (ie, different amounts transferred). I've also dumped packets from the switch into WireShark but cannot seem to find any anomaly yet (I'm looking at packets around the time the issue appeared and at the time when I reset the NIC). Any suggestions for what to look for? Ideas on what could be causing this? I'm seeing some transmit/receive errors on the NIC from both the router and switch side but nothing serious when compared to the total packet counts. I'm seriously doubting hardware at this point, as I have tried another switch, different cables, and a different NIC on the router.

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• Pinging an external server through OpenVPN tunnel doesn’t work

  - by qdii

  I have an OpenVPN server and a client, and I want to use this tunnel to access not only 10.0.8.0/24 but the whole internet. So far, pinging the server from the client through the tun0 interface works, and vice versa. However, pinging www.google.com from the client through tun0 doesn’t work (all packets are lost). I figured that I should configure the server so that any packet coming from tun0 in destination of the internet be forwarded, so I came up with this iptables config line: interface_connecting_to_the_internet='eth0' interface_openvpn='tun0' internet_ip_address=`ifconfig "$interface_connecting_to_the_internet" | sed -n s'/.*inet \([0-9.]*\).*/\1/p'` iptables -t nat -A POSTROUTING -o "${interface_connecting_to_the_internet}" -j SNAT --to-source "${internet_ip_address}" echo '1' > /proc/sys/net/ipv4/ip_forward Yet, this doesn’t work, the packets are still lost and I am wondering what could possibly be wrong with my setup. Some details: ip route gives on the server: default via 176.31.127.254 dev eth0 metric 3 10.8.0.0/24 via 10.8.0.2 dev tun0 10.8.0.2 dev tun0 proto kernel scope link src 10.8.0.1 127.0.0.0/8 via 127.0.0.1 dev lo 176.31.127.0/24 dev eth0 proto kernel scope link src 176.31.127.109 ip route gives on the client: default via 192.168.1.1 dev wlan0 proto static 10.8.0.1 via 10.8.0.5 dev tun0 10.8.0.5 dev tun0 proto kernel scope link src 10.8.0.6 127.0.0.0/8 via 127.0.0.1 dev lo scope link 192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.109 client uses wifi adapter wlan0 and TUN adapter tun0. server uses ethernet adapter eth0 and TUN adapter tun0. the VPN spans on 10.0.8.0/24 both client and linux are using Linux 3.6.1.

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• OpenVPN: ifup tap0 drops all connections

  - by raspi

  I'm trying to create star shaped "virtual" LAN with OpenVPN which is not connected to physical network. ie. tap0 packets should not go to eth0. Packet should only go through OpenVPN to connected clients. This setup works with my OpenVPN testing machine which runs Virtual Box but not on my actual server which is running on top of Xen. Both servers are running Ubuntu Intrepid. /etc/network/interfaces: iface tap0 inet manual address 10.10.10.1 netmask 255.255.255.0 gateway 10.10.10.1 /etc/openvpn/server.conf mode server tls-server port 1194 proto udp dev tap client-to-client ca /etc/openvpn/easy-rsa/keys/ca.crt cert /etc/openvpn/easy-rsa/keys/servername.crt key /etc/openvpn/easy-rsa/keys/servername.key dh /etc/openvpn/easy-rsa/keys/dh384.pem ifconfig-pool-persist ipp.txt server-bridge 10.10.10.1 255.255.255.0 10.10.10.128 10.10.10.250 push .route 10.10.10.1 255.255.255.0 keepalive 5 60 comp-lzo persist-key persist-tun status /var/log/openvpn-status.log log-append /var/log/openvpn.log verb 3 user nobody group nogroup ifup tap0 on Virtual Box: everything ok, SSH keeps running. But on Xen SSH connection drops and I have to reboot whole machine. What I'm missing?

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• Unable to connect to FTP server using Filezilla with router in-between

  - by pkswatch

  While connecting to my web server using filezilla, i am getting this error: Status: Resolving address of ftp.mysite.org.in Status: Connecting to 199.199.199.18:21... Status: Connection established, waiting for welcome message... Response: 220---------- Welcome to Pure-FTPd [privsep] [TLS] ---------- Response: 220-You are user number 1 of 150 allowed. Response: 220-Local time is now 17:58. Server port: 21. Response: 220-This is a private system - No anonymous login Response: 220-IPv6 connections are also welcome on this server. Response: 220 You will be disconnected after 5 minutes of inactivity. Command: AUTH TLS Response: 234 AUTH TLS OK. Status: Initializing TLS... Error: GnuTLS error -9: A TLS packet with unexpected length was received. Status: Server did not properly shut down TLS connection Error: Could not connect to server I use a cradlepoint CTR35 wifi router to connect to the wired internet connection. When i connect to the same server without this router, the connection works flawlessly. So i guess there is some problem with my router firewall settings, but i dont know what! Can somebody help me out please? Note: The server requires EXPLICIT FTP OVER TLS and does not work with plain FTP sessions. And i can connect to other servers using plain FTP with the router in between.

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• How to monitor changes in the frequency of network latency spikes over time?

  - by dequis

  I'm currently trying to troubleshoot an issue with my network in which I get latency spikes up to 200 seconds (normally around 50 secs) in an apparently random way at apparently random moments of the day. While trying to find what part of my messy network needs to be blamed (outside of the scope of this question - discussed a bit on chat), I realized I have no reliable way to confirm that a change actually improved anything. So far, the main way in which i notice this is that irssi shows [Lag: 15 (??)] in the statusbar, increasing every 5 seconds, and all other connections seem to be affected too. Since this depends on my observations, it's not a very reliable method to know how often it really happens. Note that just sending ICMP pings is probably not enough, but that's just my guess. It might be a "bufferbloat" issue, it might be packet loss, it might only apply to persistent connections. I suspect this because a few months ago, when the issue started, I had a "ping" command running in background and it didn't show anything weird at all during the latency spikes. This seems to have changed now (pings don't go through), but still, I'd prefer something more robust.

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• migrating Solaris to RH: network latency issue, tcp window size & other tcp parameters

  - by Bastien

  Hello I have a client/server app (Java) that I'm migrating from Solaris to RH Linux. since I started running it in RH, I noticed some issues related to latency. I managed to isolate the problem that looks like this: client sends 5 messages (32 bytes each) in a row (same application timestamp) to the server. server echos messages. client receives replies and prints round trip time for each msg. in Solaris, all is well: I get ALL 5 replies at the same time, roughly 80ms after having sent original messages (client & server are several thousands miles away from each other: my ping RTT is 80ms, all normal). in RH, first 3 messages are echoed normally (they arrive 80ms after they've been sent), however the following 2 arrive 80ms later (so total 160ms RTT). the pattern is always the same. clearly looked like a TCP problem. on my solaris box, I had previously configured the tcp stack with 2 specific options: disable nagle algorithm globally set tcp_deferred_acks_max to 0 on RH, it's not possible to disable nagle globally, but I disabled it on all of my apps' sockets (TCP_NODELAY). so I started playing with tcpdump (on the server machine), and compared both outputs: SOLARIS: 22 2.085645 client server TCP 56150 > 6006 [PSH, ACK] Seq=111 Ack=106 Win=66672 Len=22 "MSG_1 RCV" 23 2.085680 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=133 Win=50400 Len=0 24 2.085908 client server TCP 56150 > 6006 [PSH, ACK] Seq=133 Ack=106 Win=66672 Len=22 "MSG_2 RCV" 25 2.085925 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=155 Win=50400 Len=0 26 2.086175 client server TCP 56150 > 6006 [PSH, ACK] Seq=155 Ack=106 Win=66672 Len=22 "MSG_3 RCV" 27 2.086192 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=177 Win=50400 Len=0 28 2.086243 server client TCP 6006 > 56150 [PSH, ACK] Seq=106 Ack=177 Win=50400 Len=21 "MSG_1 ECHO" 29 2.086440 client server TCP 56150 > 6006 [PSH, ACK] Seq=177 Ack=106 Win=66672 Len=22 "MSG_4 RCV" 30 2.086454 server client TCP 6006 > 56150 [ACK] Seq=127 Ack=199 Win=50400 Len=0 31 2.086659 server client TCP 6006 > 56150 [PSH, ACK] Seq=127 Ack=199 Win=50400 Len=21 "MSG_2 ECHO" 32 2.086708 client server TCP 56150 > 6006 [PSH, ACK] Seq=199 Ack=106 Win=66672 Len=22 "MSG_5 RCV" 33 2.086721 server client TCP 6006 > 56150 [ACK] Seq=148 Ack=221 Win=50400 Len=0 34 2.086947 server client TCP 6006 > 56150 [PSH, ACK] Seq=148 Ack=221 Win=50400 Len=21 "MSG_3 ECHO" 35 2.087196 server client TCP 6006 > 56150 [PSH, ACK] Seq=169 Ack=221 Win=50400 Len=21 "MSG_4 ECHO" 36 2.087500 server client TCP 6006 > 56150 [PSH, ACK] Seq=190 Ack=221 Win=50400 Len=21 "MSG_5 ECHO" 37 2.165390 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=148 Win=66632 Len=0 38 2.166314 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=190 Win=66588 Len=0 39 2.364135 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=211 Win=66568 Len=0 REDHAT: 17 2.081163 client server TCP 55879 > 6006 [PSH, ACK] Seq=111 Ack=106 Win=66672 Len=22 "MSG_1 RCV" 18 2.081178 server client TCP 6006 > 55879 [ACK] Seq=106 Ack=133 Win=5888 Len=0 19 2.081297 server client TCP 6006 > 55879 [PSH, ACK] Seq=106 Ack=133 Win=5888 Len=21 "MSG_1 ECHO" 20 2.081711 client server TCP 55879 > 6006 [PSH, ACK] Seq=133 Ack=106 Win=66672 Len=22 "MSG_2 RCV" 21 2.081761 client server TCP 55879 > 6006 [PSH, ACK] Seq=155 Ack=106 Win=66672 Len=22 "MSG_3 RCV" 22 2.081846 server client TCP 6006 > 55879 [PSH, ACK] Seq=127 Ack=177 Win=5888 Len=21 "MSG_2 ECHO" 23 2.081995 server client TCP 6006 > 55879 [PSH, ACK] Seq=148 Ack=177 Win=5888 Len=21 "MSG_3 ECHO" 24 2.082011 client server TCP 55879 > 6006 [PSH, ACK] Seq=177 Ack=106 Win=66672 Len=22 "MSG_4 RCV" 25 2.082362 client server TCP 55879 > 6006 [PSH, ACK] Seq=199 Ack=106 Win=66672 Len=22 "MSG_5 RCV" 26 2.082377 server client TCP 6006 > 55879 [ACK] Seq=169 Ack=221 Win=5888 Len=0 27 2.171003 client server TCP 55879 > 6006 [ACK] Seq=221 Ack=148 Win=66632 Len=0 28 2.171019 server client TCP 6006 > 55879 [PSH, ACK] Seq=169 Ack=221 Win=5888 Len=42 "MSG_4 ECHO + MSG_5 ECHO" 29 2.257498 client server TCP 55879 > 6006 [ACK] Seq=221 Ack=211 Win=66568 Len=0 so, I got confirmation things are not working correctly for RH: packet 28 is sent TOO LATE, it looks like the server is waiting for packet 27's ACK before doing anything. seems to me it's the most likely reason... then I realized that the "Win" parameters are different on Solaris & RH dumps: 50400 on Solaris, only 5888 on RH. that's another hint... I read the doc about the slide window & buffer window, and played around with the rcvBuffer & sendBuffer in java on my sockets, but never managed to change this 5888 value to anything else (I checked each time directly with tcpdump). does anybody know how to do this ? I'm having a hard time getting definitive information, as in some cases there's "auto-negotiation" that I might need to bypass, etc... I eventually managed to get only partially rid of my initial problem by setting the "tcp_slow_start_after_idle" parameter to 0 on RH, but it did not change the "win" parameter at all. the same problem was there for the first 4 groups of 5 messages, with TCP retransmission & TCP Dup ACK in tcpdump, then the problem disappeared altogether for all following groups of 5 messages. It doesn't seem like a very clean and/or generic solution to me. I'd really like to reproduce the exact same conditions under both OSes. I'll keep researching, but any help from TCP gurus would be greatly appreciated ! thanks !

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• Win8/7/XP print spooler not getting along with Zebra ZT230 via WIFI

  - by Jonathan M

  I have a graphics-intensive 4"x6" label I'm printing to the ZT230. I'm printing multiple (10) copies. When connected via USB, all goes well. However, when connected via wifi, I only get 2 of the labels. A wireshark capture shows that at some point in the process my computer (presumably my windows spooler) is sending a reset packet, which, I believe, would pretty much kill the print job. I'm getting the same results on Win8, Win7 and WinXP. The print job was originally generated on Zebra's ZebraDesigner2 software. For easier diagnosis, I captured it to a .prn file. The .prn file can be found here: https://drive.google.com/file/d/0BwxF_9SAkKzLLTF5bUJVT0lESUU/edit?usp=sharing And the wireshark capture file can be found here: https://drive.google.com/file/d/0BwxF_9SAkKzLTGpSS0ktZW1xV28/edit?usp=sharing And the printer configuration listing: https://docs.google.com/document/d/1zh1Tw4D4yNa2uljOIL1kO2z8se9HK859irpUEwyxlyY/edit?usp=sharing I've started a discussion with Zebra Tech Support, and they're working on it, but I thought I'd toss it out here for more ideas since we're getting kind of stumped. Any ideas why this may be happening?

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• Why am I seeing MailSlot Browse messages on unrouted ports of my Linux box?

  - by nmichaels

  I have a Linux box (Debian squeeze) with several NICs. The ones of interest are: eth3 - my main link to the network (dhcp on 10.20.30.0/24) eth0 - the first connection to my test network (static: 192.168.1.2) eth4 - the second connection to my test network (static: 192.168.1.1) My routing table looks like this: $ sudo route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.20.30.0 * 255.255.255.0 U 0 0 0 eth3 default 10.20.30.254 0.0.0.0 UG 0 0 0 eth3 I have the 2 test net ports connected to each other with a crossover cable and an instance of wireshark running on each port. Every once in a while, I'll see a packet like the following show up. Who could be doing this, and how do I convince them to stop? I do have Samba running on the machine (for a cifs mount) but don't see why it would be sending packets out to unrouted ports. I had a Windows VM running in VMWare Client and thought that might be causing it, but it still happens without it. What I want is totally silent interfaces so I can run some tests with Scapy over them.

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• Total newb having SSH and remote MySQL access problems

  - by kscott

  I don't often work with linux or need to SSH into remote MySQL databases, so pardon my ignorance. For months I had been using the HeidiSQL client application to remotely access a MySQL database. Today two things happened: the DB moved to a new server and I updated HeidiSQL, now I cannot log in to the MySQL server, when attempting I get this message from Heidi: SQL Error (2003) in statement #0: Can't connect to MySQL server on 'localhost' (10061) If I use Putty, I can connect to the server and get MySQL access through command line, including fetching data from the DB. I assume this means my credentials and address are correct, but do not understand why putting those same details into HeidiSQL's SSH tunnel info won't work. I also downloaded the MySQL Workbench and attempted to set up a connection through that client and got this message: Cannot Connect to Database Server Your connection attempt failed for user 'myusername' from your host to server at localhost:3306: Lost connection to MySQL server at 'reading initial communication packet', system error: 0 Please: 1 Check that mysql is running on server localhost 2 Check that mysql is running on port 3306 (note: 3306 is the default, but this can be changed) 3 Check the myusername has rights to connect to localhost from your address (mysql rights define what clients can connect to the server and from which machines) 4 Make sure you are both providing a password if needed and using the correct password for localhost connecting from the host address you're connecting from From Googling around I see that it could be related to the MySQL bind-address, but I am a third party sub-contractor with no access to the MySQL settings of this box and the system admin is assuring me that I'm an idiot and need to figure it out on my end. This is completely possible but I don't know what else to try. Edit 1 - The client settings I am using In Heidi and MySQL Workbench I am using the following: SSH host + port: theHostnameOfTheRemoteServer.com:22 {this is the same host I can Putty to} SSH Username: mySSHusername {the same user name I use for my Putty connection} SSH Password: mySSHpassword {the same password for the Putty connection} Local port: 3307 MySQL host: theHostnameOfTheRemoteServer.com MySQL User: mySQLusername {which I can connect with once in with Putty} MySQL Password: mySQLpassword {which works once in with Putty} Port: 3306

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• NETKEY IPsec and ARP

  - by Shawn J. Goff

  I'm wondering if I have the correct routing setup for an IPsec tunnel. I have control over the IPsec endpoints and the hosts connected to one side. These hosts are connecting to the tunnel so that they have access to the network on the other side of what I will call the IPsec server. I don't have control of the network upstream of this server. Normally, the IPsec server will not respond to ARP requests for the hosts on the other side of the tunnel. So when a packet arrives for one of my hosts the server gets ARP requests, but the upstream router gets no response, and cannot construct the ethernet frame to send me the packets. If I was using one of the swan stacks, I would have a separate interface, and I'd probably just need to turn on proxyarp, but I'm using NETKEY, which doesn't use a separate interface for the tunnel. To solve the problem for now, I have added an eth0.5 vlan to the IPsec server, turned on proxyarp for that interface, and added all routes my hosts addresses to that interface so that it will respond to those ARP requests (and will therefore get relevant packets routed to it). This works, but it feels wrong. What is the correct way to get the upstream router to send me the traffic for these hosts?

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• Problem with PXE boot

  - by user70523

  I followed the following link for PXE boot, http://www.howtoforge.com/setting-up-a-pxe-install-server-on-ubuntu-9.10-p3 and I was able to ping the client from the server and also when I booted up the client It is getting the IP address from the server. But later,I got this error PXELinux 3.82 2009-06-09 . . . [other informations] !PXE Entry point found (we hope) at 9D3B:0109 via plan A UNDI code segment at 9D3B len 16C2 UNDI data segment at 933B len A000 Getting cached packet 01 02 03 . . . [other informations] TFTP prefix: Trying to load: pxelinux.cfg/ec5db4c0-74fe-d511-b9e7-3d9235afe5a1 Trying to load: pxelinux.cfg/01-00-17-31-b6-5e-a8 Trying to load: pxelinux.cfg/0A64491E Trying to load: pxelinux.cfg/0A64491 Trying to load: pxelinux.cfg/0A6449 Trying to load: pxelinux.cfg/0A644 Trying to load: pxelinux.cfg/0A64 Trying to load: pxelinux.cfg/0A6 Trying to load: pxelinux.cfg/0A Trying to load: pxelinux.cfg/0 Trying to load: pxelinux.cfg/default Unable to locate configuration file Boot failed: press a key to retry or wait for reset I have put all the files mentioned in the link in tftpboot. Can anyone explain what could be the problem. Thanks in advance

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• Firefox is very slow when establish SSL sessions

  - by yanglei

  Using wireshark, I discovered that Firefox v3.0 gets stuck every time before "client key exchange, change cipher spec" stage when establishing a SSL session. Specifically, it takes 0.8~1.8 second before Firefox send "Client Key Exchange" request. This is unacceptable since our application is HTTPS only. I tested this on IE6 and IE8, both works well. Any clues? [Update] Finally, I found the reason of 1 ~ 2 seconds stuck by displaying all captured packets in Wireshark. After the "server hello" stage, Firefox makes a request to ocsp.verisign.com combined with an additional DNS lookup for that domain. Firefox must wait the revocation status from OCSP before entering the next stage of SSL. Depends on whether DNS cache is in effect, this process takes 1 ~ 2 seconds. A interesting observation is that the IP packet contains "client key exchange" has a high possibility to get lost and thus a TCP retransmission is necessary. When this happens, the process can take 3 seconds at worst. I'm not sure if this is a coincidence or a bug. Anyway, here is the result from Wireshark: (delta-time) 0.369296 src-ip dst-ip TCP [ACK] Seq=161 Ack=2741 Win=65340 Len=0 2.538835 src-ip dst-ip TLSv1 Client Key Exchange, Change Cipher Spec, Finished 2.987034 src-ip dst-ip TLSv1 [TCP Retransmission] Client Key Exchange, Change Cipher Spec, Finished The difference between Firefox and IE is this: Firefox 3 enables OCSP checking by default where as IE only supports it. So, there is no problem with both IE6 and IE8. This is indeed a "certificate revoke" problem. Thanks

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• Possible DNS issue after a reinstall of Windows Server 2000 (get off my lawn)

  - by cop1152

  I just replaced a drive on a Win2000 Server that replicates AD and issues out DHCP at one of our offices. I successfully joined it to the domain, setup range of IP's, etc, but am still having issues. I cannot RDC to it with name or IP. I can ping it, browse to it with Windows Explorer, and remote to it with some other software, but not RDC. The other issue is this: Users are unable to authenticate on it. They receive the message 'username or password incorrect' (or something like that). Changes made on the main domain controller seem to take forever to trickle down. The most significant entry in the DNS Server Log is Event ID 7062: The DNS Server Encountered a Packet Addressed to Itself. At least, I think its significant. The Directory Services Log shows numerous Event IDs 1265: The attempt to establish a replication link with parameters failed with the following status: The DSA operation is unable to proceed because of a DNS lookup failure. Does this make any sense to anyone? I feel like its something very simple that I am overlooking. Thanks in advance.

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• MS SQL Server Firewall Ports

  - by mmacaulay

  Hi, I've recently found myself in the position of quickly deploying a production app on SQL Server 2008 (EXPRESS), and I've been having some issues with configuring firewall rules between our web server running the ASP.NET app and our database server. Everything that I can find on the internet claims that I should only need to have TCP ports 1433/1434 and UDP port 1434 accessible on the database server. However, we were unable to get connectivity going between the web app and the database with just those ports. With the help of one of the guys in our datacentre, we discovered that there was traffic also going to TCP port 2242 on the database server. After opening this port, everything worked, but we're not sure why. Later on, I had to reinstall SQL Server due to some disk space issues, and found that the problem had resurfaced - after another session with the packet sniffer, we discovered that this time traffic was going to TCP port 4541 on the database server. My question is, is there some configuration option that I'm missing in SQL server that's making it choose random ports? I'd like to have our firewall rules locked down as much as possible, and of course we'd like to avoid any future mysterious connectivity issues, especially once the app is live. Both servers are running Windows 2003 R2 X64.

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• ISA Server dropping packets as it believes they are spoofed

  - by RB

  We have ISA Server 2004 running on Windows Server 2003 SP2. It has 2 NICs - one internal called LAN on 192.168.16.2, with a subnet of 255.255.255.0, and one external called WAN on 93.x.x.2. The default gateway is 93.x.x.1 (our modem). This machine also accepts VPN connections. We are having a problem with a scanner, which is trying to save a scan into a network share. Every time we try to scan, ISA Server logs the following Denied Connection Log type: Firewall service Status: A packet was dropped because ISA Server determined that the source IP address is spoofed. Rule: Source: Internal ( 192.168.16.54:1024) Destination: Internal ( 192.168.16.255:137) Protocol: NetBios Name Service Pinging 192.168.16.54 from the ISA Server works fine. In ISA Server, going into Configuration → Networks, there are 5 Networks : - External (inbuilt) - Internal (defined as 192.168.16.0 → 192.168.16.255) - Local Host (inbuilt) - Quarantined VPN Clients (inbuilt) - VPN Clients (inbuilt) Finally, under Network Connections → Advanced → Advanced Settings..., the connections are in the following order : - LAN - WAN - [Remote Access Connections] If we try to scan onto a workstation it works fine. Please let me know if you need any more info - many thanks. RB.

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• Debugging "clogged" TCP connections

  - by Nikratio

  I'm having trouble with an internet connection that seems to randomly "freeze" arbitrary tcp connections. The connections stay established, but no data is coming through. When this happens, netstat still shows the connection status as ESTABLISHED on both the local computer: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 53 192.168.0.10:41129 173.255.235.238:143 ESTABLISHED 8219/gnutls-cli on (79.31/13/0) ..and the remote server: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 0 173.255.235.238:143 68.5.174.98:41129 ESTABLISHED 5303/imapd off (0.00/0/0) However, it seems that no data at all is transferred. If I run strace on the local and remote process, both just show a repeating sequence of select calls (with different fds of course), e.g. select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) The internet connection overall does not seem affected, I can still establish new connections to the same service on the same server without any problems. However, the affected local applications seem to be unaware of the problem and just hang. When I look at a packet capture of this connection on the client side, the last thing that happens is that the client transmits some data, then nothing happens for about 1100 seconds, and then several TCP Retransmission requests go out, with intervals increasing from 4 seconds to 130 seconds. No activity is captured after that. After about 10 minutes, the connection on the remote end disappears from the netstat (I wasn't able to catch any intermediate state), but still stays ESTABLISHED on the local end. Finally, after some more minutes, the local application aborts with a timeout and disappears from the local netstat output as well. Does anyone have a suggestion of how I could debug this further to find out where the problem lies and how to fix it? Additionaly and/or as a temporary workaround: is is there some way to globally reduce the timeout on client and/or server to reduce the time before the local application aborts?

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