A basic routing question

NightEye00

Hello everyone,

I'd like to inquire, what can be the root cause of the following configuration in my PT-lab:

2 routers (R0 and R1) connecting to each other via subnet 172.31.0.0 /16 (R0: 172.31.0.1 /16, R1: 172.31.0.2 /16)

R0: 172.30.0.1 /16 on the LAN interface towards 1 host with IP 172.30.0.2 /16, gateway set to 172.30.0.1
R1: 172.29.0.1 /16 on the LAN interface towards 1 host with IP 172.29.0.2 /16, gateway set to 172.29.0.1

Pings from 172.30.0.2 go until 172.31.0.1 but not to 172.31.0.2.
From 172.29.0.2 (the other host connected to R1) the matter is the same, pings go until 172.31.0.2 but not to 172.31.0.1.

Every interface are configured correctly, IPs/masks/gateways are OK, routing tables list all the subnets and addresses.

However, pings don't travel through the whole network, from host to host: from 172.30.0.2 to 172.29.0.2.

Do you have any idea what can cause this trouble?

Thanks!

Priston

My guess would be
R0 can ping host with IP 172.30.0.2 because it's directly connected.
R1 can't ping host with IP 172.30.0.2 because it doesn't have a route to the 172.30.0.0/16 network.

If you don't have any static or dynamic routing configured not everything will ping each other.

koz24

Can you post your PT file?

anspectrum

Routers are dumb devices like other electronic systems. We need to build intelligence in them if we want them to work as required. In your case when hosts try to ping the non-directly connected router's interface, the ping does reach to that particular router. But that router does not know how to send the reply back, because it has no information about that host network ( as we call it route). Adding static routes for the hosts networks onto the 2 x routers will fix the issue. Alternatively you can use Routing protocols which are more efficient and less administrative overhead (manual work).

Hope that helped.

v1ral

What is your routing? Static I assume? Seems like you may not have the proper routes back.

Post your PT files. It's really hard for me to understand without visual aid.

NightEye00

anspectrum wrote: »

Routers are dumb devices like other electronic systems. We need to build intelligence in them if we want them to work as required. In your case when hosts try to ping the non-directly connected router's interface, the ping does reach to that particular router. But that router does not know how to send the reply back, because it has no information about that host network ( as we call it route). Adding static routes for the hosts networks onto the 2 x routers will fix the issue. Alternatively you can use Routing protocols which are more efficient and less administrative overhead (manual work).

Hope that helped.

Yes, it was the problem!
Thank you!
I somehow thought if I configure the IPs themselves, routers will know the correct routes to forward packets in the right direction.

Thanks!

DCD

That will help you with your NAT problem too.

NightEye00

DCD wrote: »

That will help you with your NAT problem too.

Yes I realized it as well, however I didn't tried it yet but I'm sure it will work correctly

Thanks again!