Next hop query

[pgyogeshkumar]

Hi,

Suppose if I have below topology and the ipaddresses of each router in out interfaces are assigned as per the details given below.

inR1out--->inR2out---->inR3out

Can i configure static route at R1 as below so as to reach 10.10.12.0/24 network.

ip route 10.10.12.0 255.255.255.0 10.10.11.2

ip route 10.10.11.0 255.255.255.0 10.10.10.2

However in R2 i havent configured route for 10.10.12.0 network.. Will R1 traffic directly reach to 10.10.11.2 based on the next hop defined in R1 for 10.10.12.0/24 network ?

IP details:

R1 out-->10.10.10.1/24

R2 in-->10.10.10.2/24

R2 out-->10.10.11.1/24

R3 in-->10.10.11.2/24

R3 out --> 10.10.12.1/24

Apologies if my query is not clear, I can explain again. 

[Jon Marshall]

No it won't work.

R1 looks for a route for 10.10.12.x and will find a next hop IP of 10.10.11.2 which is R3's IP address. It doesn't have a directly connected interface in that subnet so it then has to do a route lookup for 10.10.11.2 and finds a route via a next hop of 10.10.10.2.

The packet is then sent to R2 with a destination IP of 10.10.12.x. Note that nothing in the packet records 10.10.11.2 which is the next hop for 10.10.12.0/24.

So the packet then arrives at R2 with a destination IP of 10.10.12.x but there is no matching route so the packet cannot be forwarded to R3.

Key point is that each router does a route lookup in isolation from all other routers.

Jon