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Issue with Netgear GS108T Managed Switch and Jumbo Frames

- by Richie086

I recently purchased a Netgear GS108T managed switch and I am trying to configure jumbo packets between my NAS (Thecus N4100Pro), PC and managed switch. I should mention the fact that I was able to use jumbo frames between my PC and NAS before I purchased the switch without issue. My Desktop has a wired gigabit NIC (Intel 82579V Gigabit) and has the ability to configure jumbo frames (see pic) that are either 9014 bytes or 4088 bytes. I choose 9014 bytes for the jumbo frame size My NAS supports jumbo frames as well, and is configured to use 9014 as the frame size. When I go into my Netgear managed switch and set the frame size to 9014 on the ports I am using for my PC and NAS. See image As soon as I hit apply in the web interface, I loose my connection to the SMB shares on my NAS and I can no longer connect to the web admin interface for my NAS. The really strange thing is I can ping my NAS via the ping command, but when I try to connect to the web interface on port 80 or port 443 the page never loads. I did a scan from my PC to my NAS using nmap and I can see the following ports open PORT STATE SERVICE 22/tcp open ssh 80/tcp open http 111/tcp open rpcbind 139/tcp open netbios-ssn 443/tcp open https 445/tcp open microsoft-ds 631/tcp open ipp 2000/tcp open cisco-sccp 2049/tcp open nfs 3260/tcp open iscsi 49152/tcp open unknown MAC Address: 00:14:FD:15:00:44 (Thecus Technology) Read data files from: C:\Program Files (x86)\Nmap Nmap done: 1 IP address (1 host up) scanned in 211.97 seconds Raw packets sent: 1 (28B) | Rcvd: 1 (28B) Anyone have any idea what is going on here? Why is nmap able to detect the ports are open and listening for http, https and file sharing but I cant connect when all devices have jumbo packets enabled? Stranger still - I did a packet capture using wireshark while the nmap scan was running and filtered so I only saw converstations between my PC and my NAS. Here are the packet details from my scan Only 4 packets over 5k bytes? What is going on here? Do I not need to configure jumbo frame sizes on the switch? I have an internet connection from my pc to the switch to my router - I just cannot connect to my NAS. I just checked on my iPhone and I am able to open my NAS web admin interface without issue on my iPhone! WTF!!!!!! Let me know if you need more details..

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netcat/socat no response from other networking services

- by jack

Hi gurus First, I thought that this was Vmware problem : http://serverfault.com/questions/141838/vmware-problems-networking-no-packet-response But now, after testing on several physical machines, I realized certain services didn't return response data when using socat/netcat 1.1 which is supposed to the latest version since last updated. root@test3:~# netcat 192.168.1.2 25 220 762462a8c4d Microsoft ESMTP MAIL Service, Version: 6.0.2600.5949 ready at Fri, 12 May 2010 18:04:20 +0800 EHLO SAYHELLO VRFY TEST@LOCALHOST EHLO localhost sdfsafsd ^ root@test3:~# I've tested it on both windows and linuxes. I found no problem with telnet.

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Author.dll status code?

- by CrazyNick

Is there a way to find any info., using /_vti_bin/_vti_aut /author.dll status code? Is there a way to find any info., using /_vti_bin/_vti_aut /author.dll status code? vermeer RPC packet method= status= status=393226 osstatus=0 msg=The form submission cannot be processed because it exceeded the maximum length allowed by the Web administrator. Please resubmit the form with less data. osmsg=

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After segment lost TCP connection never recovers

- by mvladic

Take a look at following trace taken with Wireshark: http://dl.dropbox.com/u/145579/trace1.pcap or http://dl.dropbox.com/u/145579/trace2.pcap I will repeat here an interesting part (from trace1.pcap): No. Time Source Destination Protocol Length Info 1850 2012-02-09 13:44:32.609 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=581704 Win=65392 Len=0 1851 2012-02-09 13:44:32.610 192.168.4.213 172.22.37.4 COTP 550 DT TPDU (0) [COTP fragment, 509 bytes] 1852 2012-02-09 13:44:32.639 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1853 2012-02-09 13:44:32.639 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=582736 Win=65392 Len=0 1854 2012-02-09 13:44:32.657 192.168.4.213 172.22.37.4 TCP 590 [TCP Previous segment lost] 62479 > iso-tsap [ACK] Seq=583232 Ack=345 Win=65191 Len=536 1855 2012-02-09 13:44:32.657 192.168.4.213 172.22.37.4 TCP 108 [TCP segment of a reassembled PDU] 1856 2012-02-09 13:44:32.657 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1853#1] iso-tsap > 62479 [ACK] Seq=345 Ack=582736 Win=65392 Len=0 1857 2012-02-09 13:44:32.657 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1853#2] iso-tsap > 62479 [ACK] Seq=345 Ack=582736 Win=65392 Len=0 1858 2012-02-09 13:44:32.675 192.168.4.213 172.22.37.4 COTP 590 [TCP Fast Retransmission] DT TPDU (0) [COTP fragment, 509 bytes] 1859 2012-02-09 13:44:32.715 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1860 2012-02-09 13:44:32.715 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=583272 Win=65392 Len=0 1861 2012-02-09 13:44:32.796 192.168.4.213 172.22.37.4 COTP 590 [TCP Retransmission] DT TPDU (0) EOT 1862 2012-02-09 13:44:32.945 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1863 2012-02-09 13:44:32.945 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=583808 Win=65392 Len=0 1864 2012-02-09 13:44:32.963 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1865 2012-02-09 13:44:32.963 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1863#1] iso-tsap > 62479 [ACK] Seq=345 Ack=583808 Win=65392 Len=0 1866 2012-02-09 13:44:32.963 192.168.4.213 172.22.37.4 TCP 576 [TCP segment of a reassembled PDU] 1867 2012-02-09 13:44:32.963 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1863#2] iso-tsap > 62479 [ACK] Seq=345 Ack=583808 Win=65392 Len=0 1868 2012-02-09 13:44:33.235 192.168.4.213 172.22.37.4 COTP 590 [TCP Retransmission] DT TPDU (0) [COTP fragment, 509 bytes] 1869 2012-02-09 13:44:33.434 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=584344 Win=65392 Len=0 1870 2012-02-09 13:44:33.447 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1871 2012-02-09 13:44:33.447 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1869#1] iso-tsap > 62479 [ACK] Seq=345 Ack=584344 Win=65392 Len=0 1872 2012-02-09 13:44:33.806 192.168.4.213 172.22.37.4 COTP 590 [TCP Retransmission] DT TPDU (0) [COTP fragment, 509 bytes] 1873 2012-02-09 13:44:34.006 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=584880 Win=65392 Len=0 1874 2012-02-09 13:44:34.018 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1875 2012-02-09 13:44:34.018 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1873#1] iso-tsap > 62479 [ACK] Seq=345 Ack=584880 Win=65392 Len=0 1876 2012-02-09 13:44:34.932 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1877 2012-02-09 13:44:35.132 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=585416 Win=65392 Len=0 1878 2012-02-09 13:44:35.144 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1879 2012-02-09 13:44:35.144 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1877#1] iso-tsap > 62479 [ACK] Seq=345 Ack=585416 Win=65392 Len=0 1880 2012-02-09 13:44:37.172 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1881 2012-02-09 13:44:37.372 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=585952 Win=65392 Len=0 1882 2012-02-09 13:44:37.385 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1883 2012-02-09 13:44:37.385 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1881#1] iso-tsap > 62479 [ACK] Seq=345 Ack=585952 Win=65392 Len=0 1884 2012-02-09 13:44:41.632 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1885 2012-02-09 13:44:41.832 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=586488 Win=65392 Len=0 1886 2012-02-09 13:44:41.844 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1887 2012-02-09 13:44:41.844 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1885#1] iso-tsap > 62479 [ACK] Seq=345 Ack=586488 Win=65392 Len=0 1888 2012-02-09 13:44:50.554 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1889 2012-02-09 13:44:50.753 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=587024 Win=65392 Len=0 1890 2012-02-09 13:44:50.766 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1891 2012-02-09 13:44:50.766 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1889#1] iso-tsap > 62479 [ACK] Seq=345 Ack=587024 Win=65392 Len=0 1892 2012-02-09 13:45:08.385 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1893 2012-02-09 13:45:08.585 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=587560 Win=65392 Len=0 1894 2012-02-09 13:45:08.598 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1895 2012-02-09 13:45:08.598 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1893#1] iso-tsap > 62479 [ACK] Seq=345 Ack=587560 Win=65392 Len=0 1896 2012-02-09 13:45:44.059 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] 1897 2012-02-09 13:45:44.259 172.22.37.4 192.168.4.213 TCP 54 iso-tsap > 62479 [ACK] Seq=345 Ack=588096 Win=65392 Len=0 1898 2012-02-09 13:45:44.272 192.168.4.213 172.22.37.4 COTP 590 DT TPDU (0) [COTP fragment, 509 bytes] 1899 2012-02-09 13:45:44.272 172.22.37.4 192.168.4.213 TCP 54 [TCP Dup ACK 1897#1] iso-tsap > 62479 [ACK] Seq=345 Ack=588096 Win=65392 Len=0 1900 2012-02-09 13:46:55.386 192.168.4.213 172.22.37.4 TCP 590 [TCP Retransmission] [TCP segment of a reassembled PDU] Some background information (not much, unfortunately, as I'm responsible only for server part): Server (172.22.37.4) is Windows Server 2008 R2 and client (192.168.4.213) is Ericsson telephone exchange of whom I do not know much. Client sends a file to server using FTAM protocol. This problem happens very often. I think, either client or server is doing sliding window protocol wrong. Server sends dup ack, client retransmits lost packet, but soon after client sends packets with wrong seq. Again, Server sends dup ack, client retransmits lost packet - but, this time with longer retransmission timeout. Again, client sends packet with wrong seq. Etc... Retransmission timeout grows to circa 4 minutes and communications never recovers to normal.

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[SOLVED] netcat/socat no response from other networking services

- by jack

Hi gurus First, I thought that this was Vmware problem : http://serverfault.com/questions/141838/vmware-problems-networking-no-packet-response But now, after testing on several physical machines, I realized certain services didn't return response data when using socat/netcat 1.1 which is supposed to the latest version since last updated. root@test3:~# netcat 192.168.1.2 25 220 762462a8c4d Microsoft ESMTP MAIL Service, Version: 6.0.2600.5949 ready at Fri, 12 May 2010 18:04:20 +0600 EHLO localhost sdfsafsd ^ root@test3:~# I've tested it on both windows and linuxes. I found no problem with telnet.

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Is there any USB2.0 data transfer chunk size limit?

- by goldenmean

With one read() or write() at a time, can we increase the bulk data size over USB interface? For example, I want to transfer chunk of 1024 (1K) bytes data and if the device has limitations of only 64bytes, is there any way I can increase the packet size for read() and write() system call over USB? Is there any limitation on size of data transfer over USB in a host-device environment?

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How to Break Up Large tcpdump Files

- by Kyle Brandt

Is there something that can break up tcpdump file after the captuure and make sure the breaks are on the border of packet data? Like -C but after the fact.

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OpenVPN not sending traffic to internet?

- by coleifer

I've set up openvpn on my pi and am running into a small issue. I can connect to the VPN server and ping it just fine, and I can also connect to other machines on my local network. However I am unable, when connected to the VPN, to reach the outside world (either by name lookup or IP). here are the details: On the server the tun0 interface: tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 10.8.0.1 netmask 255.255.255.255 destination 10.8.0.2 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 100 (UNSPEC) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 I can ping it just fine: # ping -c 3 10.8.0.1 PING 10.8.0.1 (10.8.0.1) 56(84) bytes of data. 64 bytes from 10.8.0.1: icmp_seq=1 ttl=64 time=0.159 ms 64 bytes from 10.8.0.1: icmp_seq=2 ttl=64 time=0.155 ms 64 bytes from 10.8.0.1: icmp_seq=3 ttl=64 time=0.156 ms --- 10.8.0.1 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2002ms Routing table # ip route show default via 192.168.1.1 dev eth0 metric 204 10.8.0.0/24 via 10.8.0.2 dev tun0 10.8.0.2 dev tun0 proto kernel scope link src 10.8.0.1 192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.6 metric 204 I also have ip traffic forwarding: net.ipv4.ip_forward = 1 I do not have any custom iptables rules (that I'm aware of). On the client, I can connect to the VPN. Here is my tun0: tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500 inet 10.8.0.6 netmask 255.255.255.255 destination 10.8.0.5 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 100 (UNSPEC) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 21 bytes 1527 (1.4 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 And on the client I can ping it: sudo ping -c 3 10.8.0.6 PING 10.8.0.6 (10.8.0.6) 56(84) bytes of data. 64 bytes from 10.8.0.6: icmp_seq=1 ttl=64 time=0.035 ms 64 bytes from 10.8.0.6: icmp_seq=2 ttl=64 time=0.026 ms 64 bytes from 10.8.0.6: icmp_seq=3 ttl=64 time=0.032 ms --- 10.8.0.6 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 1998ms rtt min/avg/max/mdev = 0.026/0.031/0.035/0.003 ms I can ssh from the client into another server on my LAN (192.168.1.x), however I cannot reach anything outside my LAN. Here's some of the server logs at the bottom of this gist: https://gist.github.com/coleifer/6ef95c3008f130249933/edit I am frankly out of ideas! I don't think it's my client because both my laptop and my phone (which has an openvpn client) exhibit the same behavior. I had OpenVPN installed on this pi before using debian and it worked, so I don't think it's my router but of course anything is possible.

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how does ospf control flooding?

- by iamrohitbanga

what method is used by ospf protocol to prevent looping of flooded packets for link state advertisements? The packet header does not contain any timestamp. How do the routers recognize that it is the same advertisement that they sent before?

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Satellite data in Russia?

- by Eddy

Anyone familiar with options for transmitting data in Russia? I'd be interested in hearing about low-speed packet data and faster. Not really looking at VSAT initially as I'd like to keep the power requirements low unless we find no other options.

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Win 2k3 - DNS query ?

- by nXqd

I'm learning about network and I configured DNS in 2k3. In forward zone : cntt.edu www.cntt.edu [ 192.168.188.4 ] . [ All IP / DNS configuration is right ] After that I use wireshark to catch packet when I enter www.cntt.edu in IE . I see there's no DNS here, I forward directly to 192.168.188.4, there's no query . Any problem ? Thanks for reading this :)

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Why do these ipfw delayed pipes have no effect?

- by troutwine

I'm on OSX 10.7.5 and am attempting to add some latency to the connection to my personal domain with ipfw, using this article as a guide. Normal latency: > ping -c5 troutwine.us PING troutwine.us (198.101.227.131): 56 data bytes 64 bytes from 198.101.227.131: icmp_seq=0 ttl=56 time=92.714 ms 64 bytes from 198.101.227.131: icmp_seq=1 ttl=56 time=91.436 ms 64 bytes from 198.101.227.131: icmp_seq=2 ttl=56 time=91.218 ms 64 bytes from 198.101.227.131: icmp_seq=3 ttl=56 time=91.451 ms 64 bytes from 198.101.227.131: icmp_seq=4 ttl=56 time=91.243 ms --- troutwine.us ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 91.218/91.612/92.714/0.559 ms Enabling ipfw: > sudo sysctl -w net.inet.ip.fw.enable=0 net.inet.ip.fw.enable: 1 -> 0 > sudo sysctl -w net.inet.ip.fw.enable=1 net.inet.ip.fw.enable: 0 -> 1 The configuration of the pipe: > sudo ipfw add pipe 1 ip from any to 198.101.227.131 00200 pipe 1 ip from any to any dst-ip 198.101.227.131 > sudo ipfw add pipe 2 ip from 198.101.227.131 to any 00500 pipe 2 ip from 198.101.227.131 to any > sudo ipfw pipe 1 config delay 250ms bw 1Mbit/s plr 0.1 > sudo ipfw pipe 2 config delay 250ms bw 1Mbit/s plr 0.1 The pipes are in place and configured: > sudo ipfw -a list 00100 166 14178 fwd 127.0.0.1,20559 tcp from any to me dst-port 80 in 00200 0 0 pipe 1 ip from any to 198.101.227.131 00300 0 0 pipe 2 ip from 198.101.227.131 to any 65535 37452525 32060610029 allow ip from any to any > sudo ipfw pipe list 00001: 1.000 Mbit/s 250 ms 50 sl.plr 0.100000 0 queues (1 buckets) droptail mask: 0x00 0x00000000/0x0000 -> 0x00000000/0x0000 00002: 1.000 Mbit/s 250 ms 50 sl.plr 0.100000 0 queues (1 buckets) droptail mask: 0x00 0x00000000/0x0000 -> 0x00000000/0x0000 Yet, this has had no effect: > ping -c5 troutwine.us PING troutwine.us (198.101.227.131): 56 data bytes 64 bytes from 198.101.227.131: icmp_seq=0 ttl=56 time=100.920 ms 64 bytes from 198.101.227.131: icmp_seq=1 ttl=56 time=91.648 ms 64 bytes from 198.101.227.131: icmp_seq=2 ttl=56 time=91.777 ms 64 bytes from 198.101.227.131: icmp_seq=3 ttl=56 time=91.466 ms 64 bytes from 198.101.227.131: icmp_seq=4 ttl=56 time=93.209 ms --- troutwine.us ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 91.466/93.804/100.920/3.612 ms What gives? I understand that ipfw is depreciated, but the manpage does not mention it being disabled. Also, I am not using Network Link Controller as I want to affect a single host.

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What exactly does ssh send when performing key negotiation?

- by Checkers

When explicitly specifying identity file to ssh: ssh -i ./id_rsa ... I have these lines in ssh debug trace: debug1: Offering public key: ./id_rsa debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply Does it mean ssh-generated id_rsa contains public RSA exponent as well, or ssh is sending out my private key? (which, of course, does not make sense). id_rsa format seems to be rather explicit that it contains private key with its "BEGIN PRIVATE KEY" block.

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Debugging rules in Iptables

- by codingfreak

Hi, How can I know how many packets were dropped by my iptables rules ?? Is there any debugging mechanism to see which rule is Dropping my packet or Accepting it ??

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

- by jcwx86

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

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How can I capture a process traffic?

- by Yassin

I would like to capture the traffic generated by a specific process (using Wireshark or other packet sniffer). Does anyone know how to do it? Thanks!

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Encrypting traffic on remote end of SSH tunnel

- by Aaron

Using an example of someone connecting to a VPS, an SSH tunnel will encrypt any traffic coming from the user to the VPS. Once it reaches the VPS network, the traffic is not encrypted and is easily sniffable by network administrators on that particular network. (am I understanding all that correctly?) Is there a way to have the traffic encrypted on both ends so that neither side is susceptible to packet sniffing to reveal what kind of data/traffic/protocol is being transmitted?

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Is Hacom Mars II Dual Blade good ?

- by Joachim H. Skeie

I am considering getting a Hacom Mars II Dual Blade for use as a firewall in a data-center for one of my colocated solutions. As the 1U enclosure have two identical firewalls, I am intending to use one of the firewalls as the external firewall using packet-filtering and load balancer (balancing load for my front-end nodes), while using the second as the internal firewall (as an application gateway). But I have no experience with Hacom, or pfSense firewalls. They do look really good on paper, but how are they in practice ?

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Is my Cisco switch port bad?

- by ewwhite

I've been chasing a packet-loss and network stability issue for a handful of end-users on an internal network for the past few days... These issues surfaced last week, however the location was struck by lightning six weeks ago. I was seeing 5-10% packet loss between a stack of four Cisco 2960's and several PC's and phones on the other side of a 77-meter run. The PC's were run inline with the phones over a trunked link (switchport configuration pastebin). We were seeing dropped calls and interruptions in client-server applications and Microsoft Exchange connectivity. I tried the usual troubleshooting steps remotely, having a local technician do the following during breaks in user and production activity: change cables between the wall jack and device. change patch cables between the patch panel and switch port(s). try different switch ports within the 2960 stack. change end-user devices with known-good equipment (new phones, different PC's). clear switch port interface counters and monitor incrementing errors closely. (Pastebin output of sh int) Pored over the device logs and Observium RRD graphs. No link up/down issues from the switch side. change power strips on the end-user side. test cable runs from the Cisco 2960 using test cable-diagnostics tdr int Gi4/0/9 (clean)* test cable runs with a Tripp-Lite cable tester. (clean) run diagnostics on the switch stack members. (clean) In the end, it took three changes of switch ports to find a stable solution. The only logical conclusion is that a few Cisco 2960 switch ports are bad or flaky... Not dead, but not consistent in behavior either. I'm not used to seeing individual ports die in this manner. What else can I test or check to determine if these devices are bad? Is it common for single ports to have problems, rather than a contiguous bank of ports? BTW - show cable-diagnostics tdr int Gi4/0/14 is very cool... Interface Speed Local pair Pair length Remote pair Pair status --------- ----- ---------- ------------------ ----------- -------------------- Gi4/0/14 1000M Pair A 79 +/- 0 meters Pair B Normal Pair B 75 +/- 0 meters Pair A Normal Pair C 77 +/- 0 meters Pair D Normal Pair D 79 +/- 0 meters Pair C Normal

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Server currently under DDOS, not sure what to do.

- by Volex

Hi, My web server is currently under a DDOS attack I believe, the messages log is full of these kind of messages: May 13 15:51:19 kernel: nf_conntrack: table full, dropping packet. May 13 15:51:19 last message repeated 9 times May 13 15:51:24 kernel: __ratelimit: 78 callbacks suppressed May 13 15:51:24 kernel: nf_conntrack: table full, dropping packet. May 13 15:52:06 kernel: possible SYN flooding on port 80. Sending cookies. and a netstat has a huge amount of the following: tcp 0 0 my.host.com:http bb176da0.virtua.com.br:4998 SYN_RECV tcp 0 0 my.host.com:http 187.0.43.109:2694 SYN_RECV tcp 0 0 my.host.com:http 109.229.4.145:1722 SYN_RECV tcp 0 0 my.host.com:http 189-84-163-244.sodobr:63267 SYN_RECV tcp 0 0 my.host.com:http bd66839d.virtua.com.br:3469 SYN_RECV tcp 0 0 my.host.com:http 69.101.56.190.dsl.int:52552 SYN_RECV tcp 0 0 my.host.com:http pc-62-230-47-190.cm.vt:2262 SYN_RECV tcp 0 0 my.host.com:http 189-84-163-244.sodobr:63418 SYN_RECV tcp 0 0 my.host.com:http pc-62-230-47-190.cm.vt:1741 SYN_RECV tcp 0 0 my.host.com:http zaq3d739320.zaq.ne.jp:2141 SYN_RECV tcp 0 0 my.host.com:http netacc-gpn-4-80-73.po:52676 SYN_RECV tcpdump shows: 7:11:08.564510 IP 187-4-1xx-4.xxx.ipd.brasiltelecom.net.br.54821 my.host.com.http: S 999692166:999692166(0) win 65535 17:11:08.566347 IP 114-44-171-67.dynamic.hinet.net.1129 my.host.com.http: S 605369055:605369055(0) win 65535 17:11:08.570210 IP 200-101-13-130.pvoce300.ipd.brasiltelecom.net.br.5590 my.host.com.http: S 2813379182:2813379182(0) win 16384 17:11:08.571290 IP dsl-189-143-30-99-dyn.prod-infinitum.com.mx.1615 my.host.com.http: S 281542700:281542700(0) win 65535 17:11:08.583847 IP dsl-189-143-30-99-dyn.prod-infinitum.com.mx.1617 my.host.com.http: S 499413892:499413892(0) win 65535 17:11:08.588680 IP 170.51.229.112.2569 my.host.com.http: S 2195084898:2195084898(0) win 65535 17:11:08.588773 IP gw2-1.211.ru.3180 my.host.com.http: F 2315901786:2315901786(0) ack 2620913033 win 64240 17:11:08.590656 IP 200-101-13-130.pvoce300.ipd.brasiltelecom.net.br.5614 my.host.com.http: S 2813715032:2813715032(0) win 16384 17:11:08.591212 IP 203.82.82.54.15848 my.host.com.http: S 4070423507:4070423507(0) win 16384 17:11:08.591254 IP 203.82.82.54.2545 my.host.com.http: S 1790910784:1790910784(0) win 16384 17:11:08.591289 IP 203.82.82.54.28306 my.host.com.http: S 578615626:578615626(0) win 16384 17:11:08.591591 IP gw2-1.211.ru.3191 my.host.com.http: F 2316435991:2316435991(0) ack 2634205972 win 64240 17:11:08.591790 IP 200-101-13-130.pvoce300.ipd.brasiltelecom.net.br.5593 my.host.com.http: S 2813659017:2813659017(0) win 16384 17:11:08.593691 IP gw2-1.211.ru.3203 my.host.com.http: F 2316834420:2316834420(0) ack 2629074987 win 64240 I'm not sure what I can do to limit/mitigate this, currently no webpages are being served, any help gratefully appreciated.

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I am unable to connect to my netbook from any machine on my network until the netbook has pinged it

- by Samuel Husky

I have a rather strange issue with my netbook on my local network. When trying to connect to it in any way from a remote system it does not appear to find it. However if I get the netbook to ping the machine trying to connect it mystically appears to work. Below is the ping test from my main PC to the netbook. C:\Users\Sam>ping 192.168.8.102 Pinging 192.168.8.102 with 32 bytes of data: Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Ping statistics for 192.168.8.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Now a ping from the netbook to my main PC sam@malamute ~ $ ping 192.168.8.100 PING 192.168.8.100 (192.168.8.100) 56(84) bytes of data. 64 bytes from 192.168.8.100: icmp_req=1 ttl=128 time=2.46 ms 64 bytes from 192.168.8.100: icmp_req=2 ttl=128 time=0.835 ms 64 bytes from 192.168.8.100: icmp_req=3 ttl=128 time=1.60 ms 64 bytes from 192.168.8.100: icmp_req=4 ttl=128 time=1.32 ms 64 bytes from 192.168.8.100: icmp_req=5 ttl=128 time=1.34 ms ^C --- 192.168.8.100 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4004ms rtt min/avg/max/mdev = 0.835/1.514/2.460/0.536 ms And the same ping again from the main PC after the netbook has made a connection to it C:\Users\Sam>ping 192.168.8.102 Pinging 192.168.8.102 with 32 bytes of data: Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Ping statistics for 192.168.8.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 1ms, Average = 1ms The netbook is running Gentoo and is currently connected via wireless. My main PC is running Windows 7 however I get the same result no matter what PC I use on this network. Please see this example from a CentOS machine on the same network [root@tiger ~]# ping 192.168.8.102 PING 192.168.8.102 (192.168.8.102) 56(84) bytes of data. From 192.168.8.200 icmp_seq=2 Destination Host Unreachable From 192.168.8.200 icmp_seq=3 Destination Host Unreachable From 192.168.8.200 icmp_seq=4 Destination Host Unreachable --- 192.168.8.102 ping statistics --- 6 packets transmitted, 0 received, +3 errors, 100% packet loss, time 5000ms , pipe 3 If you need any more information or require logs or config files please let me know and any assistance is greatly appreciated. Additional info: No responses on TCP dump from the netbook. Same result when booting into Ubuntu from a USB key. No issue when using a wired Ethernet connection.

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mysql-proxy got error which cause it to crash

- by nonus25

I got that message and i dont know what it is means: Oct 21 12:24:26 lex mysql-proxy: 2013-10-21 12:24:26: ((error)) last message repeated 98 times Oct 21 12:24:26 lex mysql-proxy: 2013-10-21 12:24:26: ((error)) network-mysqld-packet.c.596: COM_(0x04) should not be (OK|ERR|NULL), got: 00 Oct 21 12:24:26 lex kernel: [4163416.207121] mysql-proxy[14271] trap int3 ip:7ff96e8a4313 sp:7fffb9086ad0 error:0 Any idea what can be the cause of it ?

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Wireshark vs Netmon for precise time tagging

- by Nic

I'm using Wireshark to time tag and get some statistics on multicast traffic. When there is not much traffic, the stats looks good, but as soon as there is a bunch of packets arriving at the same time, I have stats that are not even possible (e.g. round trip time of 0ms) I'm wondering if Netmon could be more precise in time tagging packet because it is not relying on the Winpcap driver? Does anybody already faced the same situation? Thanks a lot, Nic

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"Must-have" Windows commandline tools?

- by hvtuananh

One commandline tool per answer :) WalkOnLAN This small command line utility makes possible to switch on a computer from a second one by sending a "Magic Packet". Both of computers can be located on the same LAN or on the different LAN segments. Anything else?

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Can I use TCP as DNS query protocol on Mac OS?

- by Brian

Hi, I'm using Mac OS, Snow Leopard 10.6.2, and I'm suffering from UDP packet loss during DNS query. So I tried DNS query as TCP using dig command, it worked very well. However, I can't find some control switch to change to use TCP during DNS query. Is there a way to change it in Mac OS? Thank you.

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