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New Member

2503 Ethernet duplex settings


What is the default duplex settings for 2503 ethernet (AUI) port, half or full ?

I am getting lot of collisions,CRC errors on the ethernet.

Also can the duplex settings be changed on the port , because when i type duplex ? it says unrecognised command?



Re: 2503 Ethernet duplex settings

Hi Praful,

Are you getting any syslog messages, related to collisions?

Clear the counters once, and start monitoring the show interface e0 counters, such as,

1. Collisions

2. Late collisions

YOu can additionally see the number of excessive collisions under "show controllers e0"

I think all of the 2500 interfaces are half-duplex.

Is the router connected to a hub, are there too many stations on it ??


New Member

Re: 2503 Ethernet duplex settings

I too think that default settings for the port is half duplex. Because once I change the duplex to full on the 1900 switch connected to router ethernet , router sees a syslog message as duplex mismatch and late collisions begin to increase.

I have left it to default of Half duplex, cleared the counters , still the problem persists.

Can the problem be with the ethernet cable or AUI Connector?

One syslog message says : %LANCE-3-UNDERFLO: Unit 0, underflow error

Cisco Doc Explanation:

The Ethernet hardware is requesting data faster than the system can supply it. This should never happen unless a serious malfunction has occurred.

Recommended Action:

Contact Cisco Systems.

New Member

Re: 2503 Ethernet duplex settings

Ethernet ports on cisco 2500 serie are 10 Mbit /Half duplex , and can not support full duplex operation.

So the fact you get collisions is perfectly normal. Is you see a lot of crc errors make sure the device on the other side of the connection is on half duplex too.

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