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New Member

Hi,why 2950 only trunk with dot1.q ?

i have some 2950 switch,i want to set trunk on 2950 and 3640 router,

but 2950 only support dot1.q trunk,and 3640 only support isl trunk,

can you tell me the reason ? why cisco 2950 switch cannt support isl turnk ?

and how can do ?



Re: Hi,why 2950 only trunk with dot1.q ?

The 2950 is a new type of switch. As 802.1q has become the standard for trunking, i suppose that Cisco is phasing out ISL trunking.

The way to go for you is to upgrade your IOS on the 3640.

The newer versions do support 802.1q (and ISL). It works partially with 12.1 and this was improved in 12.2.

I have made a working config with a 2620 and 12.1(17) but this needs the native vlan to be transmitted untagged.

Remember that you will need at least IP plus for this feature and check the memory requirements.

New Member

Re: Hi,why 2950 only trunk with dot1.q ?

I am trying unsuccessfully to do 802.1q trunking between a 2950 running IOS 12.0(5.3)WC(1) and a 2620 running IOS 12.1(13). Does anyone know if there is a problem with either of these IOS versions doing 802.1q trunking?

Thank you.

Cisco Employee

Re: Hi,why 2950 only trunk with dot1.q ?

It's a hardware limitation of CAT2950. What software are you running on 3640. 3640 should support dot1q

New Member

Re: Hi,why 2950 only trunk with dot1.q ?

Hi ,thank you .I have find the 3640 ios,because 3640's flash is 8M and ram is 32M,so i must to find the Minimum Release ios.thats ok ,i find it ,just c3640-is-mz.120-3c.W5.8 .It can support isl and dot1.q both.Thanks.

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