Congestion problem?

[infinity]

I have a Frame Relay network with a hub-and-spoke topology. One of the spoke sites is also serving as the Internet connection for the entire internetwork. There are seven sites in all and there is no routing protocol running on the network. This configuration has been working well for over 2 years until recently. I am now experiencing problems at the site that is providing Internet access. Here goes:

This site has 2 routers: 1 that connects to the Frame network (E0 192.168.22.1)and 1 that connects to the Internet via ISDN (E0 192.168.22.2). It is a flat network with simple static and default routes between the 2 routers. My problem is that the Internet access has become very slow and undependable. I am pretty sure that the problem lies in the Frame Relay router. I say this because when I remove the default route from the frame router (ip route 0.0.0.0 0.0.0.0 192.168.22.2) to the ISDN router, the trouble at the local site subsides. Everyone locally can access the Internet and my ping times to the router are under 3ms. As soon as I put the route back, however, my ping times begin to increase and will rise steadily past the 1800 ms mark and eventually time out. This is from a local PC pinging the default gateway! On another note, ping times from the ISP to the BRI interface also tend to increase until they timeout.

I don't know where to begin troubleshooting this. I have already replace both routers. The only hardware that hasn't been replaced is the local hub and the CSU/DSU module on the Frame Relay router.

If anyone has any suggestions as to where to begin troubleshooting this, I would be deeply grateful.

[mark-obrien]

This does sound like congestion. When you remove the default route, no site except for the local site has connectivity to the Internet (I'm assuming that the default gateway in the local site's hosts is the Internet router). Therefore, the local site is not "competing" with all the other sites in the network for Internet capacity. To see how much traffic is on your Internet connection, enter the command "show interface bri0:1" and "show interface bri0:2". Change this command to reflect your actual interface numbering. Look for the 5 minute input and output rates. If they are getting close to the maximum rate of 64 kbps, you have congestion.

Hope this helps.

Mark

[infinity]

Hi Mark, thanks for the reply. It is difficult to run troubleshooting tools after a couple of minutes with the default route in place. I seem to lose telnet connectivity after that. I will, however, go to the site tomorrow and console into the router so that I can troubleshoot more freely. I will look at the counters that you mentioned, but I also have another bit of information.... When the issue occurs, there is usually only one channel connected to the ISP even though I have the load-threshold set to kick in at 70% usage. Hmmm.

Anyway I will write back after I look at those counters. If you have anymore ideas please let me know.

Thanks!