Routers and RIP

[bnorton916]

So I setup a router with a 2.2.2.0 network on one side and a 2.2.3.0 network on the other.
It is not directly connected to either network.
I used RIP and got the expected problems.(when pinging 2.2.2.1 ir 2.2.3.1 it didn't know which RIP route to choose).

My question is what is going on exactly with the router. It is trying each network. And why do I get some "U"'s and some "."'s ?

Thanks,

Bill
p.s. Let me know if you need a picture(this was done in packet tracer)

Router#ping 2.2.2.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
U!.!U
Success rate is 40 percent (2/5), round-trip min/avg/max = 31/125/94 ms

Router#ping 2.2.2.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!U!.!
Success rate is 60 percent (3/5), round-trip min/avg/max = 31/89/94 ms

Router#ping 2.2.3.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.3.2, timeout is 2 seconds:
!U!.!
Success rate is 60 percent (3/5), round-trip min/avg/max = 31/104/94 ms

 

[unclerico]

Are you using RIPv1 or did you not issue no auto? Do you have CEF enabled? If yes, is it configured for the default of per-destination or did you change it to per-packet load balancing?

 

[bnorton916]

Sorry, it was RIPv1.

I did not issue auto-summary. I wanted it to mess up.

Don't even know what CEF is(I know I could google it).

There is no load balancing whatsoever. It just configured the interfaces, turned on RIPv1, and added some network commands.

Like I said, I know why it is messed up and how to fix it, what I don't know it why the router is acting the way it is.

I kinda expected all packets to fail, or succeed. I am just wanting to understand exactly what the router is doing in this situation.

Thanks,

Bill

 

[unclerico]

I'm assuming with the output you posted earlier that you probably have a hub and spoke topology with three routers and you're sourcing the traffic from the hub router. The reason I asked about CEF is that by default it will do per-destination (technically per flow) load-balancing. You're seeing the router try both paths because it sees two equal cost paths to network 2.0.0.0/8. Issue the command show ip CEF 2.2.2.2 internal on the same router you are sourcing the icmp traffic and you'll see how CEF is distributing the load. You can also issue debug ip packet from this same router to see how it works in real time.

If you source traffic from behind the router you are on now, you'll see things change depending on the destination address. Trace route to 2.2.2.2 and then trace to 2.2.3.1 and then to 2.1.1.1 and so on. Ping to various different addresses and youll see each flow stay on the same path, it wont go every other packet.

Read up on CEF to get a better understanding.

 

[bnorton916]

It does look like it is load balancing, but

R0# show ip CEF 2.2.2.2 internal
^
% Invalid input detected at '^' marker.

From the bottom PC
PC>tracert 2.2.2.2

Tracing route to 2.2.2.2 over a maximum of 30 hops:

1 9 ms 10 ms 10 ms 10.10.100.1
2 13 ms 93 ms 13 ms 11.11.11.1
3 24 ms 11 ms 24 ms 2.2.2.2

Trace complete.

So the 2nd packet went left.
But the 3rd packet went right.

I will read up on CEF. One thing with packet tracer is that I never fully trust it.

Thanks a lot for your help,

Bill

 

[bnorton916]

According to Odom, the router sees both paths as equal and going to the same place.

So, it attempts to load balance over both links.

Thanks,

Bill