IP Unnumbered combined with sub-interface help...

[BigRic]

I'm looking for some guidance on proper configs for a pair of 1720 routers. I need to route between two multi-net'd subnets over a point to point connection. Here are the specs:

R1-E0 has 10.1.1.0 /24 and 192.168.1.0 /24
R2-E0 has 10.1.2.0 / 24 and 192.168.2.0 / 24
S0 on both are connected over T1

I'd like to run unnumbered Serial interfaces using the E0 of each. My question is, to route between all subnets noted, do I simply add an IP to the E0 interface for the second subnet or do I need to create a sub-interface (e0.1) and a second IP unnumbered for a sub on the S0 too? Anyone write me a quick config?

Thanks in advance,
Eric

 

[KiscoKid]

Ideally best would be to use sub-interfaces but as you only have ethernet and not fast ethernet, your device won't support 802.1q trunking. However the following config should be fine

r1 config:

int e0
ip address 10.1.1.1 255.255.255.0
ip address 192.168.1.1 255.255.255.0 secondary

int s0
ip unnumbered e0

ip route 10.1.2.0 255.255.255.0 s0
ip route 192.168.2.0 255.255.255.0 s0



r2 config:

int e0
ip address 10.1.2.1 255.255.255.0
ip address 192.168.2.1 255.255.255.0 secondary

int s0
ip unnumbered e0

ip route 10.1.1.0 255.255.255.0 s0
ip route 192.168.1.0 255.255.255.0 s0

 

[BigRic]

Thanks for the quick response! In the event I had to do the same on a newer router with FE ports, what would the differences be? Also, in a sub-interface config - what would you do on the unnumbered interface definitions? Would you need two or just one?

Thanks again!
Eric

 

[KiscoKid]

If your router was changed to FE and you wanted to deploy dot1q trumking, you'd also have to deploy VLANs at each site and deploy each IP subnet into their own VLANs (unless you've done that already). If all the above, your configs would look like:

r1 config:

int fa0
no ip address
int fa0.1
encapsulation dot1q 1
ip address 10.1.1.1 255.255.255.0
int fa0.2
encapsulation dot1q 2
ip address 192.168.1.1 255.255.255.0

int s0
ip unnumbered fa0.1

ip route 10.1.2.0 255.255.255.0 s0
ip route 192.168.2.0 255.255.255.0 s0



r2 config:

int fa0
no ip address
int fa0.1
encapsulation dot1q 1
ip address 10.1.2.1 255.255.255.0
int fa0.2
encapsulation dot1q 2
ip address 192.168.2.1 255.255.255.0

int s0
ip unnumbered fa0.1

ip route 10.1.1.0 255.255.255.0 s0
ip route 192.168.1.0 255.255.255.0 s0