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Community Member

Packet loss on a 2621 interface

I know this is very general, but I have a router that is getting as much as 15% packet loss with large packets (up to 1500 bytes). The MTU on both router interfaces is 1500. The router fastethernet interface is directly connected to a 2500 ethernet interface. Going into the local network no loss. Going to the 2500 losses up to 15% with large packets. No loss on smaller packets. I have an idea what the problem is, but was wondering what others thought.


Community Member

Re: Packet loss on a 2621 interface

If you do a "show int" on both routers, do you see any collisions/CRC/etc...type errors?

There might be a speed/duplexing issue between the two routers.

Good luck!

Community Member

Re: Packet loss on a 2621 interface

Yes, there are CRC errors. the 2500 is at 10 mb and the 2621 is at 10 mb - both half duplex. However, the BW on the 2621 shows 100000. I assume that means the maximum possible and not what it is actually communicating at. Below is the relevant entry:

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliablility 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Half-duplex, 10Mb/s, 100BaseTX/FX

What do you think? The other 2621 interface is definitely at 100 mb and full duplex. My thoughts were that I should hard code both to 10 mb half duplex.



Community Member

Re: Packet loss on a 2621 interface


Try hard coding the speed and duplex to half-10 on both routers, clear the counters on both interfaces and see if you're still getting some errors.

Hopefully that should fix the problem.


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