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Interface Resets and Ethernet lockups

I'm getting serial0 interface resets and a suspicious number of input frame errors. The resets appear to be in response to a hung serial line coincident with an apparent ethernet lock up.

We've tried a 1604, 1601, and 1721 routers with an 1DSU FT1 WIC to a P2P Full T1 circuit. The Ethernet side goes to a 2900 switch. One switch port goes to a Linux box with a 2nd NIC to a 10.0.0.* network. The other switch ports go to streaming and web servers. There is much outbound traffic, but little incoming.

The T1 side has no errors (show service-module looks clean). Is it reasonable to assume that the T1 side, including wiring, is not suspect?

Is there a buffer issue on the serial line, or is it most likely to be something locking the ethernet port?

I'm sniffing packets at this point, but I'm looking for some experience to help narrow my field of search on this one. Of course, an obvious quick fix would be fine too. We haven't been able to find any yet ;-)

Thanks in advance.

Jon.

2 REPLIES

Re: Interface Resets and Ethernet lockups

Ok Jon, one thing to keep in mind when working with T1 or E1 lines is that you need to have proper grounding for your equipment.

Especially when you are experiencing error bursts as described.

http://www.cisco.com/en/US/products/hw/modules/ps2641/products_module_installation_guide_chapter09186a008007cb4c.html

regards,

Leo

New Member

Re: Interface Resets and Ethernet lockups

Thanks Leo.

I'll be adding a ground strap to the router chassis and lifting the AC ground (to avoid loops) tonight. A ground noise/hum has been on my mind for a while. I'll have the techs test the on-campus segment for grounds, noise, resistance, etc. as well.

Other than these problems, I'm curious what else could cause the ethernet side to hang. What evidence should I look for in the packets besides a period of inactivity coincident with the "lockup"?

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