Multihoming Ethernet problem

[davemonk]

Hi,

I've read a few of the comments about multi-homing an Ethernet interface, but I can't seem to get to the bottom of the issue that I'm having.

I'm attempting to add a third IP address to my Ethernet0/0 interface. In my config I've the following:

ip address ip_addr_1 255.255.255.240

ip address ip_addr_2 255.255.255.0

Adding a third (ip address ip_addr_3 255.255.255.0) everything appears to be fine ("sh run" lists all three) but when reboot I get an error message :

"Secondary addresses are not allowed with negotiated addresses"

This appears twice, and as a result the 2600 boots up with just ip_addr_1 bound to the interface.

Any ideas out there???

[thisisshanky]

I m not sure whether there is a workaround for this in new IOSes, but secondary ip addresses cannot be used on an interface, which is configured with a command, "ip address negotiated".

[davemonk]

Looking around some more on the net, I too came up with this - but there's nowhere in my config where "ip address negotiated" appears. (It would seem that this is used when initialising a PPP connection)

I've even tried pulling out both addresses (I seem to remember coming across this problem before and remembering that it had something to do with the order in which the interfaces were put in) but even that doesn't work!

[wbaker17]

Dave

I am not sure what you mean by multi-homing on the ethernet interface of a 2600, so I am making a guess here. Are you trying to add secondary IP addresses for additional subnets to the interface?

ip address 192.168.1.1 255.255.255.0

ip address 192.168.2.1 255.255.255.0 secondary

ip address 192.168.3.1 255.255.255.0 secondary

Hope this helps some.

Bill

[davemonk]

Bill,

Exactly what I'm after and is exactly what you have listed here (use of the "secondary" switch)

From my config:

interface Ethernet0/0

ip address 192.168.2.1 255.255.255.0 secondary

ip address 192.168.30.1 255.255.255.0 secondary

ip address 200.200.200.50 255.255.255.240

Note that 200.200.200.50 isn't my actual allocated address << for security's sake ;o) >> but it's subnet is from a /28 network

Surely the order in which the config is entered isn't an issue and the secondary's are listed before the true ip address just because the config is sorted in numerical order?