Hi,

While going through some syslog stuff this morning I've noticed that a couple of switches are complaining about duplex mismatches on trunk interfaces. When I took a closer look, two switches (switches 1 & 3) are reporting that they have a duplex mismatch to a device connected to a downstream switch (switch 2).

Basic topology is switch 2 has a 1G fibre link to both switch 1 & 3.

For example, on switch 1:

I get the same thing from switch 3, just with a different interface listed.

Duplex settings between the 3 switches are all fine.

Checking on switch 2 shows that the device is connected to g0/20, which is definitely half duplex.



I've had a look at other switches that have one of these devices connected (it's a cisco ATA-186 if anyone is interested) and they aren't doing this so I'm presuming this isn't an expected behaviour.

CCO suggests disabling CDP v2 if there is a non cisco device in between the 2 switches reporting issues, but all 3 of these are cisco, anyone have any other suggestions?

Switch 1 - WS-C3750X-24S 12.2(58)SE2
Switch 2 - WS-C3560E-24PD 12.2(52)SE
Switch 3 - WS-C3750G-12S 12.2(55)SE

Cheers

J

My first question is why are you running gig interfaces at 10/half?!?!

The fact that they auto-negotiated to 10/half is concerning. That would indicate to me that something prevented auto-negotiation from working correctly. If it did work right you'd be at 1000/Full.

The errors you're seeing are due to the information contained in the CDP messages not matching. They may be indicative of an issue, but they may not be. In this case I'd double check the interface configurations on both ends, and maybe check the cable between them. You also say duplex settings are fine... What are the duplex settings? If you have one side set to full, and the other set to auto then the auto side will default to half because auto-negotiation is broken. Set both sides to auto.

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Hi,

Thanks for the reply.


I'm informed by my colleagues in the telecoms department that the ATA only runs at 10/half, it does seem a waste but we only have gig switches in that cabinet.


I don't think its the cables, these are all fibre links (apart from the one to the ATA). Although I haven't swapped them out since seeing this issue, I know they were swapped out recently as part of a building refurb.


I'm presuming that as these are SFP's they default to full duplex, I certainly can't change it to anything else.

Cheers

J

Are there phones connected to the switches? What device is SEP1C17D33702E7?

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I don't have a signature.

Yes, all cisco phones.

SEP1C17D33702E7 is a cisco ATA, full details below.


Cheers

J

We have a few Cisco ATA's in our environment and we hard code the switchports to 10\HALF.

Hardcode your switchport to 10half for the ATA 186, it doesn't negotiate at all. You get the error because your switchport is on auto and the device is hardcoded.

You get the same result since the device actually works in half-duplex, but you normally either hardcode both sides or put them both in autonegotiation.

http://www.cisco.com/en/US/docs/voice_ip_comm/cata/186_188/2_15_ms/english/administration/guide/sccp/sccpach1.html


Note: The Cisco ATA 188 performs auto-negotiation for duplexity and speed and is capable of 10/100 Mbps, full-duplex operation. The Cisco ATA 186 is fixed at 10 Mbps, half-duplex operation.

Thanks for the suggestions, I've hardcoded the port, but we are still getting the log entries.

Cheers

J

Can you post the log entry, the config from the interface in question and the output of 'show cdp nei detail' for that particular interface.

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David
CCIE R&S #38338, CCIP, CCNP

http://networkbroadcast.co.uk - My Blog
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Hi,

Yep, here you are.

Log entry from switch 1:

I presume you mean the interface with the ATA on switch 2 as opposed to the inter switch links?
CDP neighbour detail:


Cheers

J

[quote="Jericho"]Hi,




You have configured gi1/0/20 as 10/half, but the log entry is for gi1/0/5; therefore, CDP is giving the error message for another port. Also noticed that 'cdp neighbor detail' shows the same ID as in the log on a different port. Has the phone been moved?

--Richard

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http://justnetworked.wordpress.com

That's what I'm trying to work out.

The ATA is connected to port g0/20 on switch2.
Switch 2 is connected to g1/0/5 on switch1.
I'm getting duplex mismatches on switch 1 referring to the ATA connected to switch2.

Cheers

J