| Venue: | Seminar Room 833 |
| Time: | 19th May 2000(14:30 - 15:30) |
| Target Audiences: | GA who set up linux hosts in research lab |
Seminar Outline
Looks at the Ierrs, Oerrs and Collis
netstat -i
Name Mtu Net/Dest Address Ipkts Ierrs Opkts Oerrs Collis Queue
le0 1500 ethernet grsun1 653637 20 116339 1 1478 0
lo0 1536 127.0.0.0 localhost 193 0 193 0 0 0
the Ierrs/Ipkts and Oerrs/Opkts should be < 0.025 %
Large Ierrs => the interface just discards the packet
=> there may be fautly hardware on the network
(Faulty hardware can be anything from another
computer system that is generating packets
improperly to a bad connector or terminator)
=> or your system cannot receive packets fastenough
(use spray to check it)
Large Oerrs => your system's network infterface is faulty.
=> something wrong the CPU and the ethernet cable
=> the problem should be local not from outsiders
(we can do a loop back testing for the
ethernet interface
"test net" at the o.k. prompt )
Collisions are normal evernts and don't indicate hardware
problems. However, if Collis/Opkts > 10 % constanly
=> network overloaded
We may use the snoop, tcpdump, tcptop, and
protocol analyser to trace the source of the network traffic
(e.g the broadcast messages or NFS packets)
ttcp -t -s -n65535 -l 8192 ntec5 ttcp-t: buflen=8192, nbuf=65535, align=16384/0, port=5001 tcp -> ntec5 ttcp-t: socket ttcp-t: connect ttcp-t: 536862720 bytes in 56.61 real seconds = 9260.74 KB/sec +++ ttcp-t: 65535 I/O calls, msec/call = 0.88, calls/sec = 1157.59 ttcp-t: 0.2user 13.2sys 0:56real 23% 0i+0d 0maxrss 0+2pf 0+0csw ftp> bin 200 Type set to I. ftp> get very_large_file /dev/null local: /dev/null remote: very_large_file 200 PORT command successful. 150 Opening BINARY mode data connection for very_large_file (29491200 bytes). 226 Transfer complete. 29491200 bytes received in 3.1 seconds (9.2e+03 Kbytes/s)
csh> ping ntec5 PING ntec5.ie.cuhk.edu.hk (137.189.99.85) from 137.189.99.81 : 56(84) bytes of data. 64 bytes from 137.189.99.85: icmp_seq=0 ttl=255 time=0.2 ms 64 bytes from 137.189.99.85: icmp_seq=1 ttl=255 time=0.1 ms 64 bytes from 137.189.99.85: icmp_seq=2 ttl=255 time=0.1 ms 64 bytes from 137.189.99.85: icmp_seq=3 ttl=255 time=0.1 ms 64 bytes from 137.189.99.85: icmp_seq=4 ttl=255 time=0.1 ms 64 bytes from 137.189.99.85: icmp_seq=5 ttl=255 time=0.1 ms 64 bytes from 137.189.99.85: icmp_seq=6 ttl=255 time=0.1 ms csh> arp ntec5 ntec5 (137.189.99.85) at 0:d0:9:27:66:18 csh> traceroute www.cuhk.edu.hk traceroute to spring.csc.cuhk.edu.hk (137.189.6.37), 30 hops max, 40 byte packets 1 router-99 (137.189.99.254) 1 ms 1 ms 1 ms 2 137.189.200.250 (137.189.200.250) 2 ms 2 ms 1 ms 3 csc0g03brb.net.cuhk.edu.hk (137.189.192.253) 2 ms 2 ms 2 ms 4 spring.csc.cuhk.edu.hk (137.189.6.37) 2 ms * 2 ms csh> traceroute www.ust.hk traceroute to www.ust.hk (143.89.14.34), 30 hops max, 40 byte packets 1 router-99 (137.189.99.254) 1 ms 1 ms 1 ms 2 137.189.200.250 (137.189.200.250) 2 ms 2 ms 2 ms 3 a4-0.rs1.hkix.net (202.40.161.254) 2 ms 5 ms 2 ms 4 harnet-yck-atm.hkix.net (202.40.161.245) 4 ms 4 ms 4 ms 5 192.245.196.74 (192.245.196.74) 5 ms 12 ms 6 ms 6 cis7k6-fw.ust.hk (202.40.138.125) 6 ms 6 ms 6 ms 7 www.ust.hk (143.89.14.34) 6 ms * 8 ms
csh> tcpdump -e broadcast 07:19:28.958674 eth0 B 0:10:4b:a:a9:68 Broadcast arp 60: arp who-has ieugp12.ie.cuhk.edu.hk tell ieugp1.ie.cuhk.edu.hk 07:19:29.073106 eth0 B 0:10:4b:a:a9:68 Broadcast arp 60: arp who-has ieugp8.ie.cuhk.edu.hk tell ieugp1.ie.cuhk.edu.hk 07:19:29.252125 eth0 B 0:10:4b:a:a9:68 Broadcast arp 60: arp who-has ieugp13.ie.cuhk.edu.hk tell ieugp1.ie.cuhk.edu.hk 07:19:29.385745 eth0 B 0:c0:4f:7a:3d:c5 Broadcast arp 60: arp who-has ielabpc.ie.cuhk.edu.hk tell ielabnt0.ie.cuhk.edu.hk 07:19:29.392456 eth0 B 0:60:97:67:13:6e Broadcast 8137 110: 07:19:29.427844 eth0 B 0:10:4b:a:a9:68 Broadcast arp 60: arp who-has ieugp3.ie.cuhk.edu.hk tell ieugp1.ie.cuhk.edu.hk 07:19:29.639623 eth0 B 0:e0:4f:61:a8:80 Broadcast 8137 494: 07:19:29.695659 eth0 B 0:e0:4f:61:a8:80 Broadcast 8137 494: 07:19:29.751534 eth0 B 0:e0:4f:61:a8:80 Broadcast 8137 494: