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Community Member

ISL and 802.1q


I'm configuring a 4006 with a network module 4418 gb with 2 Uplink port and 16 overbloked port (do not support ISL encapsulation) and one 48 x 10/100 port .. Actually we use 8 switches from 3500 family they have all a Giga link on a 3508 and a backup link on a 3548 , we have configured Spanning tree load balancingport priority (giga for Uplink and one of the fa for backup ) These switches use ISL encapsulation The Plan is to migrate these switches on the 4006 , but I need to turn off the ISL encapsulation on the 3500 Switches and then let the giga port on negotiatet mode .. but I can let the FA port with ISL , So At the end I will have ISL on the FA port and on giga port 802.1q .. IS IT GOOD ??

Thank you

Community Member

Re: ISL and 802.1q

I think for general support issues, I would implement only one trunking protocol. I am sure it will work by mixing and matching the protocol, but you could have support issues when trying to resolve a problem.

Since your Cat 4000's support 802.1q, thats the one I would go with.

Someone else may be able to verfy this, but I believe Cisco has made some kind of annoucement endorsing the use of 802.1q over ISL?? Anyone?


Community Member

Re: ISL and 802.1q

I agree. Stay with the standard 802.1q, that way you can trunk to anyones

switch. And, FYI, if you every go to a Catalyst 2950 switch, they ONLY support

802.1q. You won't even be able to set the encap option because the default

is forced to 802.1q. This sounds like an endorsement to me....

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