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

[blue balls]

If I disable eth1 with

   ifdown eth1

the results of the same commands are:

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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> mtu 1500 qdisc pfifo_fast state DOWN 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> mtu 1500 qdisc pfifo_fast state DOWN 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
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 
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
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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