I have two 2620's with a CSU/DSU in each.
Router A fas0/0 is 10.102.3.254, s0/0 10.103.3.1, Router B fas0/0 is 10.102.32.245, S0/0 10.103.3.2
I got the T1 side to come up up. I enabled IP routing on both routers. Now when I plug into the ehternet on either I can ping the fas0/0 and the s0/0 of that router but no further from a PC. The routers can ping each others interfaces. This should be working without a routing protocol becaue they are directly connected right? Any suggestions?
Without a routing protocol (or static routes) each router will know about the subnet on the FastEthernet interface and the subnet that connects it to the other router. But it would not have any knowledge of the subnet on the FastEthernet of the other router.
To make it work you would either need to have a dynamic routing protocol running or would need to configure static routes on each router for the remote destination subnets.
Also make sure that any PC connected to either subnet has correct IP address and correcct default gateway configured.
you will need either static or dynamic routing information about the remote networks.
Have a look at a routers IP routing table (show ip route) and you will find no entry for the remote routers LAN. If there is no entry in the IP routing table a router will drop the IP packet.
So enable dynamic routing or use static routing, f.e.
ip route 10.102.32.0 255.255.255.0 10.103.3.2
ip route 10.102.3.0 255.255.255.0 10.103.3.1
Make sure the mask is set correctly for your environment (you did not mention it, so I assumed /24).
Hope this helps! PLease rate all posts.
But I should be able to ping the opposite side serial interface. I am plugged into the fas of router A and can ping s0/0 of router A but not of router B. It is the same subnet so I should be able to ping that opposite side because it is directly connected. Right?
I believe that the problem is this: when your PC attempts to ping the serial of the remote router, the ping packet from your PC gets to the remote router, but the remote router does not have routing information to send the response to your PC and therefore drops the packet and the ping does not work.
The problem is the return packet. The remote router will not know the senders address in the LAN. The ICMP echo request will reach the router, but the router will not know wherer to send the ICMP echo reply - it simply does not have the network in its routing table.
Place both static routes in the routers as suggested any everything should be fine.
It worked with putting those static routes in. I guess I have a little more studying to do because I thought that directly connected routes automatically get routed. I guess that would make life too easy. What would you suggest for a routing protocol for a network of six routers all just a span off of the network to get to remote locations through T1 lines?
Thanks again for helping me out with that.
For a small network such as you describe any of the dynamic routing protocols would work fine. Many people regard RIP as a very easy protocol. It does send routing updates on a periodic basis and some people try to minimize using bandwidth on serial links with routing updates. Based on that I might suggest using EIGRP. It is easy to configure and will minimize the bandwidth used for routing updates.
RIPv2 or OSPF or EIGRP will be well suited.
F.e. a simple OSPF config, which can be applied to all routers would be
router ospf 10
network 0.0.0.0 0.0.0.0 area 0
This should work under "normal" circumstances. There are a lot of possibilities to fine tune this, but I kept it as simple as possible as a starting point.
Hope this helps! Please rate all posts.