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New Member

ISL Trunk non supported by catalyst 2950, Why ?

Old catalyst 2924XL support trunk ISL o 802.1Q,

now catalyst 2950 replay 2924XL, but support

only trunk 802.1Q, Why ?

  • Other Network Infrastructure Subjects
4 REPLIES
Cisco Employee

Re: ISL Trunk non supported by catalyst 2950, Why ?

The 2950 has a hardware limitation that prevents the use of ISL. Hardware that supports ISL is generally more expensive that hardware that just supports 802.1q. To provide a lower cost to the consumer, the switch uses hardware that does not ISL.

New Member

Re: ISL Trunk non supported by catalyst 2950, Why ?

How then, do I connect a 2950 to my existing 1900's?

since one supports ISL and the other 802.1q

New Member

Re: ISL Trunk non supported by catalyst 2950, Why ?

There is one solution, although it is a bit of a pain. Put a isl/dot1q capable device (like a 2900XL) between the 2950 and 1900. This way you can ISL from 1900 to 2900XL, then dot1q from 2900XL to 2950. I know this is not ideal, but Cisco say they have no plans to support ISL on the 2950 !

Daniel,

New Member

Re: ISL Trunk non supported by catalyst 2950, Why ?

Cisco is converting too the IEEE standard of dot1Q on all new switches they rollout. ISL is use between cisco products, since networks are now comprise of sometimes many different brands of devices, converting to the dot1q is a positive step for cisco. The 1900 switches are end of life products you should upgrade them to 2924 so you configurer trunking between the 2950 switch.

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