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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• Cisco router not receiving OSPF updates

  - by WebDevHobo

  Or at least, that's what I think is happening. There doesn't appear to be a debug command for this, or to see if something is in the routing table. I'm testing out this setup in Packet Tracer. I have 3 routers and a webserver From left to right, you have: Webserver - Router1 - Router2 - Router3 Router1 and Router2 can succesfully ping WebServer. Router3 cannot. Router2 has a default gateway set, to send all not-recognized data through its serial interface to Router1. Like this: ip route 0.0.0.0 0.0.0.0 Serial 0/0/1 Serial 0/0/1 being the connection to Router1 Router2 and Router3 have OSPF configured. From their "show run": Router2: router ospf 1 log-adjacency-changes passive-interface Serial0/0/1 network 10.1.1.0 0.0.0.3 area 0 default-information originate ! Router3: router ospf 1 log-adjacency-changes network 10.1.1.0 0.0.0.3 area 0 passive-interface FastEthernet0/0 ! I was under the assumption that setting default-information originate on Router2 would give Router3 the needed information. What's going wrong here? The interfaces are up. Ip addresses are with mask-range, clock rate is set at correct end. I don't know what else to check.

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• OpenVPN bad source address from client

  - by Bogdan

  I have one problem with OpenVPN. There are a lot drops records in the openvpn log file on the server: Mon Oct 22 10:14:41 2012 us=726541 laptop/???:1194 MULTI: bad source address from client [192.168.1.107], packet dropped grep -E "^[a-z]" server.conf ----- port 1194 proto udp dev tun ca data/ca.crt cert data/server.crt key data/server.key dh data/dh1024.pem tls-server tls-auth data/ta.key 0 remote-cert-tls client cipher AES-256-CBC tun-mtu 1200 server 10.10.10.0 255.255.255.0 ifconfig-pool-persist ipp.txt push "redirect-gateway def1 bypass-dhcp" push "dhcp-option DNS 8.8.8.8" client-to-client client-config-dir /etc/openvpn/ccd route 10.10.10.0 255.255.255.0 keepalive 10 120 comp-lzo persist-key persist-tun max-clients 5 status /var/log/status-openvpn.log log /var/log/openvpn.log verb 4 auth-user-pass-verify /etc/openvpn/verify.sh via-file tmp-dir /tmp script-security 2 ----- cat ccd/laptop ----- iroute 10.10.10.0 255.255.255.0 ----- cat client.conf ----- remote server ip 1194 client dev tun ping 10 comp-lzo proto udp tls-client tls-auth data/ta.key 1 pkcs12 data/vpn.laptop.p12 remote-cert-tls server #ns-cert-type server persist-key persist-tun cipher AES-256-CBC verb 3 pull auth-user-pass /home/user/.openvpn/users.db ----- According to "Jan Just Keijser - OpenVPN 2 Cookbook" root of the problem is incorrect config options.see the screenshot But, as you see, my config has such options. Could you please help me to solve this problem. @week Verb leverl=6; client log. Mon Oct 22 16:06:02 2012 do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0 Mon Oct 22 16:06:02 2012 /sbin/ifconfig tun0 10.10.10.3 pointopoint 10.10.10.5 mtu 1500 Mon Oct 22 16:06:02 2012 /sbin/route add -net xxxx netmask 255.255.255.255 gw 192.168.1.1 Mon Oct 22 16:06:02 2012 /sbin/route add -net 0.0.0.0 netmask 128.0.0.0 gw 10.10.10.5 Mon Oct 22 16:06:02 2012 /sbin/route add -net 128.0.0.0 netmask 128.0.0.0 gw 10.10.10.5 Mon Oct 22 16:06:02 2012 Initialization Sequence Completed cat ccd/latop iroute 10.10.10.0 255.255.255.0 ifconfig-push 10.10.10.3 10.10.10.5

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• WCF timeout exception detailed investigation

  - by Jason Kealey

  We have an application that has a WCF service (*.svc) running on IIS7 and various clients querying the service. The server is running Win 2008 Server. The clients are running either Windows 2008 Server or Windows 2003 server. I am getting the following exception, which I have seen can in fact be related to a large number of potential WCF issues. System.TimeoutException: The request channel timed out while waiting for a reply after 00:00:59.9320000. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout. ---> System.TimeoutException: The HTTP request to 'http://www.domain.com/WebServices/myservice.svc/gzip' has exceeded the allotted timeout of 00:01:00. The time allotted to this operation may have been a portion of a longer timeout. I have increased the timeout to 30min and the error still occurred. This tells me that something else is at play, because the quantity of data could never take 30min to upload or download. The error comes and goes. At the moment, it is more frequent. It does not seem to matter if I have 3 clients running simultaneously or 100, it still occurs once in a while. Most of the time, there are no timeouts but I still get a few per hour. The error comes from any of the methods that are invoked. One of these methods does not have parameters and returns a bit of data. Another takes in lots of data as a parameter but executes asynchronously. The errors always originate from the client and never reference any code on the server in the stack trace. It always ends with: at System.Net.HttpWebRequest.GetResponse() at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) On the server: I've tried (and currently have) the following binding settings: maxBufferSize="2147483647" maxReceivedMessageSize="2147483647" maxBufferPoolSize="2147483647" It does not seem to have an impact. I've tried (and currently have) the following throttling settings: <serviceThrottling maxConcurrentCalls="1500" maxConcurrentInstances="1500" maxConcurrentSessions="1500"/> It does not seem to have an impact. I currently have the following settings for the WCF service. [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Single)] I ran with ConcurrencyMode.Multiple for a while, and the error still occurred. I've tried restarting IIS, restarting my underlying SQL Server, restarting the machine. All of these don't seem to have an impact. I've tried disabling the Windows firewall. It does not seem to have an impact. On the client, I have these settings: maxReceivedMessageSize="2147483647" <system.net> <connectionManagement> <add address="*" maxconnection="16"/> </connectionManagement> </system.net> My client closes its connections: var client = new MyClient(); try { return client.GetConfigurationOptions(); } finally { client.Close(); } I have changed the registry settings to allow more outgoing connections: MaxConnectionsPerServer=24, MaxConnectionsPer1_0Server=32. I have now just recently tried SvcTraceViewer.exe. I managed to catch one exception on the client end. I see that its duration is 1 minute. Looking at the server side trace, I can see that the server is not aware of this exception. The maximum duration I can see is 10 seconds. I have looked at active database connections using exec sp_who on the server. I only have a few (2-3). I have looked at TCP connections from one client using TCPview. It usually is around 2-3 and I have seen up to 5 or 6. Simply put, I am stumped. I have tried everything I could find, and must be missing something very simple that a WCF expert would be able to see. It is my gut feeling that something is blocking my clients at the low-level (TCP), before the server actually receives the message and/or that something is queuing the messages at the server level and never letting them process. If you have any performance counters I should look at, please let me know. (please indicate what values are bad, as some of these counters are hard to decypher). Also, how could I log the WCF message size? Finally, are there any tools our there that would allow me to test how many connections I can establish between my client and server (independently from my application) Thanks for your time! Extra information added June 20th: My WCF application does something similar to the following. while (true) { Step1GetConfigurationSettingsFromServerViaWCF(); // can change between calls Step2GetWorkUnitFromServerViaWCF(); DoWorkLocally(); // takes 5-15minutes. Step3SendBackResultsToServerViaWCF(); } Using WireShark, I did see that when the error occurs, I have a five TCP retransmissions followed by a TCP reset later on. My guess is the RST is coming from WCF killing the connection. The exception report I get is from Step3 timing out. I discovered this by looking at the tcp stream "tcp.stream eq 192". I then expanded my filter to "tcp.stream eq 192 and http and http.request.method eq POST" and saw 6 POSTs during this stream. This seemed odd, so I checked with another stream such as tcp.stream eq 100. I had three POSTs, which seems a bit more normal because I am doing three calls. However, I do close my connection after every WCF call, so I would have expected one call per stream (but I don't know much about TCP). Investigating a bit more, I dumped the http packet load to disk to look at what these six calls where. 1) Step3 2) Step1 3) Step2 4) Step3 - corrupted 5) Step1 6) Step2 My guess is two concurrent clients are using the same connection, that is why I saw duplicates. However, I still have a few more issues that I can't comprehend: a) Why is the packet corrupted? Random network fluke - maybe? The load is gzipped using this sample code: http://msdn.microsoft.com/en-us/library/ms751458.aspx - Could the code be buggy once in a while when used concurrently? I should test without the gzip library. b) Why would I see step 1 & step 2 running AFTER the corrupted operation timed out? It seems to me as if these operations should not have occurred. Maybe I am not looking at the right stream because my understanding of TCP is flawed. I have other streams that occur at the same time. I should investigate other streams - a quick glance at streams 190-194 show that the Step3 POST have proper payload data (not corrupted). Pushing me to look at the gzip library again.

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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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