How does my provider route to me

Question

Hi all my service provider has a router and pix on my site, the router connects to the internet via a serial, the pix and router are on the same network, would the router be using ip unnumbered on the serial interface ? and also we have been assigned ip addresses using a x.x.255.x network, how come we can use the 255 network ?

Answer 1

Hi
I think you want to know how your provider route subnet to you.
it seems you unnumbered you serial interface to your ethernet so the serial interface uses the ethernet ip address.
at the service provider they can define a loopback interface with another ip address out of your range and unnumbered their serial interface to it ,only thing that they need is an "ip route" the configuration at service provider should like this :
NOTE ALL THIS STATEMENTs NOT REAL AND It s ONLY AN EXAMPLE
interface loopback 0
ip add 200.1.1.1 255.255.255.255
interface serial 1
ip unnumbered loopback 0
//this the interface that connect directly to you//
ip route (your network address) (mask) serial 1
like :
ip route 20.1.1.0 255.255.255.0 serial 1
in this sample 20.1.1.0 is your network range.
so you can have all of 255 ip address by assigning the ip address to your ethernet or fast ethernet and then unnumbered your serial to them.
Thanks.
hope usefull.