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New Member

NM/4E module and CRC errors

We have Cisco 3640 router with NM/4E module installed on it. This NM/4E is used for providing bandwidth to other subscribers in the same building. Bandwidth is provided in the following way.

UTP CAT5E cables are layered between our office and our subscribers office in the same building. On the subscriber's end UTP cable is terminated on a Ethernet Switch via patch panel, the subscriber's machines/servers are connected to that switch. In our office that UTP cable directly terminates to Ethernet port of NM/4E module Via patch panel. We implement traffic-shape command in order to controll the speed of link.

We are facing the problem of CRC errors on ethernet port of NM/4E module. The cable distance between our premises and subscriber office is 189 feet. The rate of these CRC errors is constant and more than normal. There are no collisions on ethernet port of NM/4E module.

IOS on cisco router is

Version 12.2(5a), RELEASE SOFTWARE (fc1)

Having the same configurations and scenario we shifted a subscriber's link from ethernet port of NM/4E module to Fast Ethernet port (Fastethernet0/1). The CRC errors counter is 0 for the last two days. This confirms that this is not a UTP cable problem, if there are CRC errors due to UTP then there should be CRC errors on Fast Ethernet port (Fastethernet0/1). From this I guess that may be there is a problem in NM/4E module and we did not configure it with correct parameters.

I need help on this problem. Many thanks in advance. Any comments and sugestions would be welcome.

New Member

Re: NM/4E module and CRC errors

Make sure you do not have "auto-negotiate" turned on on either side. Verify you have the same speed and duplex settings (10-half/10-full). I have see it in the past where the duplx settings were mismatched and caused a high number of CRC errors.

Good luck.