dual nic interface

[Craig White]

On Fri, 2007-01-19 at 11:02 -0700, Nathan Aubrey wrote:
> Let me clarify a little bit.
> The machine has one network adapter which has two physical ports in it labled 
> port1 and port2.
> 
> [root at bob ~]# ifconfig
> eth0      Link encap:Ethernet  HWaddr 00:18:8B:74:A3:B5
>           inet addr:10.0.1.9  Bcast:10.0.1.255  Mask:255.255.255.0
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:16776 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:9061 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:13611191 (12.9 Mb)  TX bytes:1029762 (1005.6 Kb)
>           Interrupt:16 Memory:f4000000-f4011100
> 
> eth1      Link encap:Ethernet  HWaddr 00:18:8B:74:A3:B3
>           inet addr:10.0.1.75  Bcast:10.0.1.255  Mask:255.255.255.0
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:79 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:8601 (8.3 Kb)  TX bytes:64 (64.0 b)
>           Interrupt:16 Memory:f8000000-f8011100
> 
> 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:4139 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:4139 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:215881 (210.8 Kb)  TX bytes:215881 (210.8 Kb)
> 
> Only eth0 is plugged in to the switch. eth1 is unplugged.
> From another workstation, 10.0.1.70, I can ping both 10.0.1.9 and 10.0.1.75.
> If I remove the cable from eth0 and plug it into eth1 I cannot ping either 
> address.
> 
> These are not :1,2,3 virtual interfaces. And I am only pinging from the 
> seperate machine, 10.0.1.70. Not on the localhost...
----
since eth0 and eth1 list different HWaddr - even though you only have 1
physical wire, you have 2 physical ports so the need to run a separate
cable is probably immaterial. It may behave differently if you have two
physical cables and you can probably manually assign them to the
physical addresses - on a Red Hat type system, the assignment for the
physical addresses is done in /etc/sysconfig/network-scripts/ifcfg-eth0
and /etc/sysconfig/network-scripts/ifcfg-eth1 though I don't recall you
stating which distribution you are using so this can vary.

Craig