IP addresses on a serial link? 1

[aballant]

Hi,

If the far-end interface on a serial link has an IP address which is not on the subnet defined locally does this cause any problems?






cheers,
Andrew

 

[commsguy]

Only if routing across that link is important to you.

commsguy

http://www.convetech.com

 

[aballant]

Hi,

In what way would this break the routing across a serial link? The router would send the packets to the next-hop address whatever that may be, from where it would be routed again.
You mean if the traffic's destination was the IP address at the far end? But the router would know the far end IP address from routing updates, so if a packet came in for that address it would know that the IP address was directly connected and send it out that interface, before performing routing.
Is this true? I'm thinking of how 'ip unnumbered' works,




cheers,
Andrew

 

[nyy1023]

The /30 address on the serial interface is nothing more than a dedicated nexhop address. This does not need to be in the same subnet that you are routing. In all of my past cases all the /30 addresses that I have assigned were froma different block of IP's set aside for this purpose. In the case of unnumbered you need to specify in the config that it is unnumbered fastethernet0

Is this what you were looking for?

 

[aballant]

Yes, indeed. I think I understand now. It is just going to be a next hop, and the subnet is redundant as there is nothing else on the subnet. Routing updates will not be affected,


cheers,
Andrew

 

[nyy1023]

yes, the /30 subnet allows for only 4 IP's
the first is the network Identifier
the second is the local host
the third is the next hop, or ISP
the last is the broadcast

the first and the last cannot be used so that leaves you with two assignable IP's to use

 

[aballant]

Many thx,

cheers,
Andrew