[Bug 530353] [NEW] Machine with 2+ interfaces will only respond to pings from same subnet

[Patrick Cable]

Public bug reported:

Binary package hint: linux-server

a VMware Virtual Machine: 
root at svc1:~# lsb_release -rd
Description:	Ubuntu 9.10
Release:	9.10

root at svc1:~# uname -a
Linux svc1 2.6.31-19-server #56-Ubuntu SMP Thu Jan 28 03:40:48 UTC 2010 x86_64 GNU/Linux

root at svc1:~# apt-cache policy linux-server
linux-server:
  Installed: 2.6.31.19.32
  Candidate: 2.6.31.19.32
  Version table:
 *** 2.6.31.19.32 0
        500 http://ubuntu.media.mit.edu karmic-updates/main Packages
        500 http://ubuntu.media.mit.edu karmic-security/main Packages
        100 /var/lib/dpkg/status
     2.6.31.14.27 0
        500 http://ubuntu.media.mit.edu karmic/main Packages


Given the following interface configuration on svc1:

root at svc1:~# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:50:56:a2:54:65  
          inet addr:192.168.67.20  Bcast:192.168.67.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea2:5465/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3926 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3907 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:928188 (928.1 KB)  TX bytes:767119 (767.1 KB)

eth1      Link encap:Ethernet  HWaddr 00:50:56:a2:4b:6d  
          inet addr:192.168.62.64  Bcast:192.168.62.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea2:4b6d/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:21967 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4411 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2651065 (2.6 MB)  TX bytes:847480 (847.4 KB)

eth2      Link encap:Ethernet  HWaddr 00:50:56:a2:49:e4  
          inet addr:192.168.63.100  Bcast:192.168.63.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea2:49e4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:19748 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3918 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2730066 (2.7 MB)  TX bytes:772363 (772.3 KB)

A client ("interceptor") with the ip 192.168.62.42 can only ping and get a response from eth1. 
root at svc1:~# tcpdump -i eth1 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
17:12:19.545318 IP interceptor > 192.168.62.64: ICMP echo request, id 42794, seq 0, length 64
17:12:19.545341 IP 192.168.62.64 > interceptor: ICMP echo reply, id 42794, seq 0, length 64
17:12:20.545399 IP interceptor > 192.168.62.64: ICMP echo request, id 42794, seq 1, length 64
17:12:20.545410 IP 192.168.62.64 > interceptor: ICMP echo reply, id 42794, seq 1, length 64

If interceptor tries to ping the other interfaces:
root at svc1:~# tcpdump -i eth0 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
17:13:39.377306 IP interceptor > 192.168.67.20: ICMP echo request, id 53034, seq 0, length 64
17:13:40.377374 IP interceptor > 192.168.67.20: ICMP echo request, id 53034, seq 1, length 64

At the time of writing, tcpdump -i eth2 shows no packets received.
However, this has typically shown a similar response as above.

To eliminate VMware ESX as an issue, i tried this out on a physical host
running ubuntu 9.10; however with an older kernel. (Linux flab
2.6.31-17-generic #54-Ubuntu SMP Thu Dec 10 17:01:44 UTC 2009 x86_64
GNU/Linux) and received similar behavior as above.

On svc1, if i down eth1 and 2, I am able to ping the subnet correctly.

** Affects: linux-meta (Ubuntu)
     Importance: Undecided
         Status: New

-- 
Machine with 2+ interfaces will only respond to pings from same subnet
https://bugs.launchpad.net/bugs/530353
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