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New Member

Trunk flaps

I have connected a dot1q trunk on gigabit interfaces between a WS-3550-24 switch ver 12.1(11)EA1 and a 4006 switch ver 6.2(1) and find that the interface of the 3550 goes up and down, but there are no errors on the interface. Is this a bug?? I have changed the cable and GBICs with no difference.

6 REPLIES

Re: Trunk flaps

Hi,

please provide some details.

How often does the trunk flap?

What are the syslog messages on both ends when the trunk flaps?

What is the trunk configuration on both ends?

Regards,

Milan

New Member

Re: Trunk flaps

Milan,

Thank you for your reply. Here are some answers to yoiur questions:

1. Trunk flaps about every 10 min.

2.no messages in the log on the 4006 switch. On the 3550 the log just says gigabit interface 0/1 is down, then up.

2. On 4006:set trunk 4/2 auto dot1q 1-13,16-1005

On 3550:interface GigabitEthernet0/1

switchport trunk encapsulation dot1q

switchport mode trunk

no ip address

Re: Trunk flaps

Hi,

AFAIK, the config should be correct.

Just one idea (not sure if it helps, but it might):

I'd try to make the trunk nonegotiate on both ends. There might be some IOS/CatOS minor incompatibilities.

Regards,

Milan

New Member

Re: Trunk flaps

Thanks Milan,

I will give that a try when I get the chance,

Regards,

Steve

Anonymous
N/A

Re: Trunk flaps

I had a similar but not exact problem between a new 3550 and 4003. TAC told me to downgrade the IOS on the 3550 to 12.1(9). That fixed the problem.

Based on how far back they wanted be to rev the IOS and the number of new versions coming out, looks like there are quite a few bugs in the new 3550 operating system.

New Member

Re: Trunk flaps

jjoy,

Thanks very much for the info.

Regards,

Steve

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