IP unnumbered

[tikual]

Hi all,

Do anyone know what is the purpose of 'ip unnumbered'? How to use it?

Thanks!

tikual

 

[ccmuser]

tikual,

Ip unnumbered is way for large networks to conserve on ip space.. It eliminates the need for individual ip networks to be assigned to every point to point link in your orginization. Used all the time in dialup and quite a bit in ATm,frame networks..

What are you trying to use it for?

 

[tikual]

ccmuser,

My english is not well, I confused the description of it from my CCNP study guide. It shown an example and using it for a discontiguous subnet communication. Actually I still not understand its meaning. Anyway, thanks for your explanation.

tikual

 

[ccmuser]

yes.. that example would make sense... When you remove the point to point like in the middle of networks you have
two discontiguous networks that need to use ipunnumbered to communicate..

 

[wybnormal]

IP unumbered is an interesting twist on ip addressing. You have to have an IP address for IP to work, yes? So if you dont have extra IPs for the WAN OR if you want to be crazy secure, you would use ip unnumbered.

To work, the router "borrows" the IP address from the Ethernet side and adds it's own MAC for the serial (wan) interface. BUt, this only works for the link. You can not telnet to an unnumbered interface or anything else that requires the IP address to be there. The way around is to use the unnumbered interface and then create a loopback interface that you CAN telnet to

MikeS


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