IP Unnumbered Question

[StarTAC]

hi guys...

i have a quick quesiton on the ip unnumbered feature...

i have a serial interface with a network 192.168.0.192/27, and the serial interface IP is 192.168.0.193.. i have created frame relay sub-interfaces that provide service to my other branches.. these sub-interfaces have no explicit IP addresses.... i am using the ip unnumbered feature on these sub-interfaces, unnumbering onto the main serial interface.. this means that the sub-interfaces take on the IP address of the main serial interface, 192.168.0.193...

now, i am close to depleting that network, and would like to expand the frame relay IPs and start another network, 192.168.0.224/28... i am using the same serial interface.. i intend to create more sub-interfaces to handle this new network...

however, since the unnumbered sub-interfaces take on the default IP address of the main serial interface, and i want to assign the second network onto the serial interface, IP 192.168.0.225, what happens to IP processing since my clients with the 192.168.0.224/28 network are being unnumbered to the default 192.168.0.193 IP of the serial interface, which is out of their IP range....

will the setup work, or is it likely there could be a problem..?..

all help appreciated..

 

[KSM]

I am not favor of ip unnumber on serial. It may cause more problems on routing and logging than save a few ip addresses.
But if you must have to do, why don't you assign the new ip address on loopback interface and configure your new sub-interface with ip unnumbered loopback<something>.
Good luck!

 

[StarTAC]

i have already set it up, and it's working fine... all necessary routing has been taken care of, and it's a procedure also recommended by Cisco....

but what i wanted to know, is what would happen when i setup a primary and secondary IP address on the serial [or any other interface, loopback or ethernet] interface, because the ip unnumbered feature will use the default/primary address of that multi-addressed interface...

what will become of IP processing when a user from the second 192.168.0.224/28 network sends a packet and it arrives on the sub-interface, which has 192.168.0.193 [different network], as it's implicit [unnumbered] IP address.....?..

all help appreciated...

 

[tschouten]

I would say create a loopback address with what you want and use the ip unnumbered command to point the sub-inter to that specific loopback address. It shouldn't cause any problems. Here is a good area on ciscos website to check out (you may have already seen it but hey it never hurts)

http://www.cisco.com/en/US/tech/tk648/tk365/technologies_tech_note09186a0080094e8d.shtml

 

[StarTAC]

i guess this is the answer i've been looking for... creating network-oriented loopback interfaces and pointing the sub-interfaces to them, accordingly, would solve my problems....

cheers mate...