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Attention: The Cisco Support Community site will be in read only mode on Dec14, 2017 from 12:01am PST to 11:30am for standard maintenance. Sorry for the inconvenience.

New Member

Port negotiating problem

Our router (2800) 'int g0/0' is hard set to 'FULL duplex' and 'Speed 100', this is connected to our backbone switch (4503), our issue is when we set the port on the 4503 to 'Duplex Auto' and 'Speed Auto' it sets itself at 'HALF duplex' and 'Speed 100'. We have replaced the cable and tried hard setting the port to 'FULL duplex', this failed and the WAN link went down. Any ideas at what could be the problem? Cheers

New Member

Re: Port negotiating problem

both sides auto negotiation won't work

See below documentation and try to keep setting as per specifications.But Even after those settings it's not working let me know the IOS version of both side devices.

Re: Port negotiating problem

can you try to set speed/duplex to auto/auto on both ends and see if it works?

after that clear counters on both interfaces and check for any errors, CRC on both interfaces.

hope it helps ... rate if it does ...


Re: Port negotiating problem

In normal case, auto/auto should work. Could you advise the LAN module no. of 4503 ? Moreover, do you mean if the LAN of 2800 down, the WAN also down ? Could you provide the config of 2800 ? It is abnormal.

Hope this helps.

New Member

Re: Port negotiating problem

Thanks guys, we had to hardset our and the telco link to 1G FULL duplex. This seems to work fine and we no longer have any issues.

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