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Community Member

SW port in CP7960

We deployed Cisco IP telephony in our office and during use we`ve founded that SW port in IP Phone which is interconnected with Cisco Catalyst 2924

(all ports are "auto" for speed and duplex)

And as I know port in IP phone also using "auto"

But in reality the switched ports _alvays_ connect in halfduplex - 100Mb, why it is so?

The answer "defind speed and duplex manualy" is not I`m looking for, as I suppose autonegotiation MUST work.

Or the situation I`m talking about is not a bug but feature?

3 REPLIES
Community Member

Re: SW port in CP7960

Be aware that auto-negotiation does not always work, even between Cisco products. When negotiation starts the devices will try to negotiate at the highest common mode of operation.

If for some reason it cannot negotiate that mode it drops down to the next mode. I have seen several cases where auto negotiation will just not work.

At the very least you could code the switch and let the phone negotiate to that mode. you might also look into the version of switch code you are running to see if there are any known issues.

I know this isn't a lot of help but maybe it can give you some ideas.

Community Member

Re: SW port in CP7960

Forgot to write description of "solution"

we usually set speed/duplex interface parameters statically, and if I use speed 100, full duplex I will get CP7960 SW port working as 100 base tx port in half duplex, but if you will change duplex in to "auto" all will be fine. But I still couldn`t understand why it works so????

Best regards

Community Member

Re: SW port in CP7960

The key is the ability to hardcode both ends of the connection....

Manually setting the speed and duplex on one link partner could result in a duplex mismatch. This is the result of disabling auto-negotiation on one link partner and the other link partner defaulting to a half-duplex configuration. A duplex mismatch will result in slow performance, intermittent connectivity, data link errors, and other issues. If the intent is not to use auto-negotiation, both link partners must be configured for speed and duplex manually.

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