Assumptions can be dangerous...

[output truncated]

eth0      Link encap:Ethernet  HWaddr 00:50:da:b4:ac:48
          inet addr:10.2.12.97  Bcast:1.255.12.255  Mask:255.255.255.0

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.2.12.0      0.0.0.0         255.255.255.0   U         0 0          0 eth0
0.0.0.0         10.2.12.1      0.0.0.0         UG        0 0          0 eth0


# ifconfig eth1 10.12.12.98 up
connection timed out.

What just happened?

Well, a further explanation is probably required.
eth0 is on a /24, and eth1 was supposed to be a /24 as well.
See the problem yet?
no?
Let's get on the console of the box:

# ifconfig 
eth0      Link encap:Ethernet  HWaddr 00:0c:29:8e:cb:a8  
          inet addr:10.12.2.97  Bcast:10.12.2.255  Mask:255.255.255.0

eth1      Link encap:Ethernet  HWaddr 00:0c:29:8e:cb:b2  
          inet addr:10.12.12.98  Bcast:10.255.255.255  Mask:255.0.0.0

See the problem? No? let's check the routing table:

# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.12.2.0       0.0.0.0         255.255.255.0   U         0 0          0 eth0
10.0.0.0        0.0.0.0         255.0.0.0       U         0 0          0 eth1
0.0.0.0         10.12.2.1       0.0.0.0         UG        0 0          0 eth0

See it now?

This is the problem with making assumptions. In this case, the operations person made the assumption that the netmask provided in their original ifconfig would be what they wanted. It obviously was not.

You now have two conflicting routes, one route for a /24 and one route for an /8.

ifconfig, if not given a netmask will default the mask to the "class" of the IP given. In this case, a 10-dot will default to a class A, or a /8.
You can imagine what happened then.

While this might seem like a simple thing, i've had 2 operations guys bring down production boxes doing just this, in less than 3 months.

The lesson: Make sure you understand the defaults of your commands.
And, change windows are your friends. They keep people from breathing down your neck when you screw up like this.