[Bug 788301] Re: Networking fails with two interfaces on the same network

[blue balls]

Tried again today, in Ubuntu 10.04 with all the updates applied, and the
bug is still there.

To Stéphane Graber (stgraber) and Daniel Hahler (blueyed), here are the
outputs of the commands when both eth0 and eth1 are "up" and the
networking doesn't work:

----------------------------------------------

root at pc1:/# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether 00:18:f3:91:08:9d brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:18:f3:91:11:eb brd ff:ff:ff:ff:ff:ff
4: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
    link/ether 00:15:af:08:f6:ea brd ff:ff:ff:ff:ff:ff

----------------------------------------------

root at pc1:/# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether 00:18:f3:91:08:9d brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.2/24 brd 192.168.1.255 scope global eth0
    inet6 fe80::218:f3ff:fe91:89d/64 scope link 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:18:f3:91:11:eb brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.3/24 brd 192.168.1.255 scope global eth1
    inet6 fe80::218:f3ff:fe91:11eb/64 scope link 
       valid_lft forever preferred_lft forever
4: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
    link/ether 00:15:af:08:f6:ea brd ff:ff:ff:ff:ff:ff

----------------------------------------------

root at pc1:/# ip route show
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.2 
192.168.1.0/24 dev eth1  proto kernel  scope link  src 192.168.1.3 
169.254.0.0/16 dev eth1  scope link  metric 1000 
default via 192.168.1.1 dev eth1  metric 100 
default via 192.168.1.1 dev eth0  metric 100 

----------------------------------------------

root at pc1:/# ip route get 1.2.3.4
1.2.3.4 via 192.168.1.1 dev eth0  src 192.168.1.2 
    cache  mtu 1500 advmss 1460 hoplimit 64

----------------------------------------------

root at pc1:/# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     *               255.255.255.0   U     0      0        0 eth0
192.168.1.0     *               255.255.255.0   U     0      0        0 eth1
link-local      *               255.255.0.0     U     1000   0        0 eth1
default         192.168.1.1     0.0.0.0         UG    100    0        0 eth1
default         192.168.1.1     0.0.0.0         UG    100    0        0 eth0

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https://bugs.launchpad.net/bugs/788301

Title:
  Networking fails with two interfaces on the same network

Status in “ifupdown” package in Ubuntu:
  Incomplete

Bug description:
  Binary package hint: ifupdown

   Summary: when two network interfaces on the same computer are
  configured on the same network, the networking fails.

    Details: I have two network interfaces eth0 and eth1 which have static addresses: 192.168.1.2 and 192.168.1.3.
    The gateway is a home router which has the address 192.168.1.1.
    When both interfaces are brought up with "ifup", I cannot connect to the Internet. When only the first on is "up" and the other one is "down", the connection to the Internet works well.

  ProblemType: Bug
  DistroRelease: Ubuntu 10.04
  Package: ifupdown 0.6.8ubuntu29.2
  ProcVersionSignature: Ubuntu 2.6.32-31.61-generic 2.6.32.32+drm33.14
  Uname: Linux 2.6.32-31-generic i686
  NonfreeKernelModules: nvidia
  Architecture: i386
  Date: Wed May 25 21:41:45 2011
  ProcEnviron:
   LANGUAGE=
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: ifupdown

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