Need help on Loopback Ip Address

[subash cobi]

Hi,

Can anyone please help me on how to configure a router with only a loopback ip address.

And without any ip address on both the lan interfaces.

I want to connect a router which has only 1 loopback ip address to my core switch 1 and core swicth 2.

Using both the LAN insterface on the router.

Thank You in advance,

Regards,

Subash

[durgeshpurohit]

Hi Subash,

A loopback IP address is just for self testing and if you are not going to configure the router interface (e.g. fa0/0/1) with an IP address then the entire communication is not possible.

A network packet need source ip and destination ip in order to reach to it's destination.

Anyone correct me if i am wrong.

Thanks,

-Durgesh

[uhaskamp]

Hi Subash,

for me it is not clear what you want to achieve with this config.

In my eyes you could configure the two LAN interfaces with bridging and the Layer 3 interface would then be a BVI (bridged virtual interface).

Then you have a direct Layer 2 connection between your two LAN interfaces as well as between your two core switches.

I don't think that an "ip unnumbered Lo0" on both LAN interfaces will have success because then you have the same subnet on two interfaces.

Udo

[subash cobi]

Hi Guys,

What i am trying to achieve is to create a loopback ip address on the router. And all communication to the router will be to the loopback ip address.

Eg.

Loopback ip : 10.10.10.1/24

Gi 0/1 : Connected to core 1 (vlan 10 = 10.10.10.0/24)

Gi 0/2 : Connected to core 2 (vlan 10 = 10.10.10.0/24).

Basicly, it is just a physical layer redundancy.

Thank You/

[uhaskamp]

Hi Subash,

in my eyes you can not do this with only the loopback.

You can try the following:

interface Gigabit 0/2
bridge-group 1
!
interface gigabit 0/1
bridge-group 1
!
interface BVI 1
ip address 10.10.10.1 255.255.255.0
!
bridge irb
bridge 1 protocol ieee
bridge 1 route ip

With this config the router will take part in the spanning tree.

Perhaps this helps.

Udo