Default Route question when there are two nic cards

Styma, Robert E (Robert) stymar at lucent.com
Wed Oct 11 20:27:59 UTC 2006


I am working with a machine with two nic cards.  One is connected
to the corporate network.  This is eth0.  The other was previously
not connected to anything.  Everything worked fine.

In setting the machine up for some work I will have to do, I did the
following:
1.  Plug a cable into the eth1 rj45 and into a small hub.
2.  Plug a laptop into that same small hub.
3.  Configure the laptop to IP address 192.168.55.55 with the gateway 192.168.55.50
4.  Using system-config-network, I brought up eth1 as 192.168.55.50 with the
    default gateway of 192.168.55.55 (the PC).  That is all that is attached to the
    other network.

The problem is that when I reboot, or service network restart, the default
route ends up on eth1 (192.168.55.55).  I can correct it by hand and everything
is OK.

I have been googling the newsgroups and poking around in the ifcfg-eth* files
and have not seen a way to tell the system that the default route is on eth0.

I must be missing something simple, can someone point me in the correct direction?
(nnn is to obscure our corporate network info)

ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:0C:76:FD:6F:17  
          inet addr:nnn.nnn.36.86  Bcast:nnn.nnn.37.255  Mask:255.255.254.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:132036 errors:0 dropped:0 overruns:0 frame:0
          TX packets:133639 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:51419035 (49.0 Mb)  TX bytes:96862625 (92.3 Mb)
          Base address:0xa000 Memory:fb000000-fb020000 

eth1      Link encap:Ethernet  HWaddr 00:0C:76:FF:3A:51  
          inet addr:192.168.55.50  Bcast:192.168.55.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:116 errors:0 dropped:0 overruns:0 frame:0
          TX packets:637 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:10202 (9.9 Kb)  TX bytes:62796 (61.3 Kb)
          Base address:0xb000 Memory:fa000000-fa020000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:42266 errors:0 dropped:0 overruns:0 frame:0
          TX packets:42266 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:4674615 (4.4 Mb)  TX bytes:4674615 (4.4 Mb)

The following is how the routing looks after service network restart (or reboot).
Then the two commands fix the problem.

netstat -r -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.55.0    0.0.0.0         255.255.255.0   U         0 0          0 eth1
nnn.nnn.36.0    0.0.0.0         255.255.254.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth1
0.0.0.0         192.168.55.55   0.0.0.0         UG        0 0          0 eth1
[lcm-phx-07-n1.phx.lucent.com]: route del -net 0.0.0.0 gw 192.168.55.55 dev eth1
[lcm-phx-07-n1.phx.lucent.com]: route add -net 0.0.0.0 gw nnn.nnn.36.1 dev eth0
[lcm-phx-07-n1.phx.lucent.com]: netstat -r -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.55.0    0.0.0.0         255.255.255.0   U         0 0          0 eth1
nnn.nnn.36.0    0.0.0.0         255.255.254.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth1
0.0.0.0         nnn.nnn.36.1    0.0.0.0         UG        0 0          0 eth0

Robert E. Styma
Principal Engineer (DMTS)
Lucent Technologies, Phoenix
Email: stymar at lucent.com / styma at swlink.net
Phone: 623-582-7323  Cell: 602-478-0114
Company:  http://www.lucent.com
Personal: http://www.styma.org




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