Packet Loss

Daniel333

Alright, so here is my configuration...
Using RIP

RouterA
s0- 10.0.0.1/8

RouterB (both DCEs)
s0- 10.0.0.2/8
s1- 10.0.0.3/8

RouterC
s0- 10.0.0.4/8


RouterA(s0) --- (s0) RouterB (s1)--- (s0) RouterC

I can ping any Ip, including it own from RouterA, except RouterC's s0.
I can ping RouterC's s0 from RouterB's s1, but half the packets are lost!
I can ping RouterB's s1 from RouterC s0, not not itself, with half the packets lost!

I can run a show cdp neig from RouterC's s0 and it clearly shows RouterB correct information.

I have set this exact same configuration up with static routes, and had no ping issues before. What would you say the next couple steps in trouble shooting would be?

What I have done
1) Swapped Cables, same results
2) Tried replacing RouterC's s0 with it's s1, and I still loose half my ICMP with ping

I am going to go from RouterA to RouterC and see if that flies in a minute, barring that, any ideas? I am really leaning to a defective router... but that would not explain the static routes working. Reinstall IOS?

marlon23

Your addressing is so wrong,..

You cannot have all routers in one subnet with that topology. You need to learn what is routing about.

Daniel333

Wow. Yeah, I am feeling pretty dumb. Put everything on it's own subnet and worked fine.

I guess that brings up the question, why did some of the ping ICMP data go through and some not? Did one half the data get shot out the other port and lost?

georgemc

What type of router is RouterB? It's been a while but I'm sure I remember that most routers(cisco) don't allow you to assign addresses from the same subnet to multiple ports. Meaning once I said "ip-address 10.0.02 255.255.0.0" on S0 when I try to do an "ip-address 10.0.0.3 255.255.0.0" on S1 the router returns and error.

Can anyone confirm this?

Did the default router behavior change in one of the many IOS upgrades over the years?

Daniel333

Router B
2505 IOS 11.1

But all my Routers allowed this, but they are all running 11.x. I would switch to 12, I have an IOS image of it, but I am not sure yet how to do to it, nor do I know the legality of doing so yet. (Although I am not too hung up on that, I just believe it's something I should fully understand, if it's something I am going to do professionally some day).

georgemc

Thanks Daniel,
I think I'll take a short break from my Microsoft studies and fire up one of my routers when I get home today and do a little testing. It's been many years since I've seen the particular error that I'm talking about because it was drilled into my head a long time ago that you don't do that. The first cisco routers I dealt with were old AGS/IGS types that ran 9.X and didn't have the ? or the fancy config prompt.

marlon23

OK, the ICMP thing...

My little guess:

Router in the middle will have two routes to that network, so he will try to ballance traffic (he can do it per packet or per destination, with RIP it depends on if route cache is enabled or disabled) so he will send one packet through one interface and another by second interface. So some packets will be lost and some wouldnt.

Am I wrong? If yes , please correct me.