Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Community Member

switch to switch config

hi,

i have layer 3 switch 4506e connected to layer 2 switch 2960

Layer 3's gig2/4 connected to layer 2's gig0/1

layer 3 gig2/4 config

switchport trunk encapsulation dot1q

switchport trunk native vlan 10

switchport mode trunk

layer 2 gig0/1 config

switchport trunk native vlan 10

switchport mode trunk

My question is we dont need to configure encapsulation at layer 2 end??

if no, why??

5 REPLIES

switch to switch config

The only thing that I can think of is that the 2960 doesn't support ISL and only supports dot1q trunking. You can see this by doing "sh inter g0/1 trunk" on the 2960. It will tell you what trunking protocol it's using. I didn't have time to look for the documentation on the 2960 though, so this is really just a guess.....

HTH, John *** Please rate all useful posts ***
Cisco Employee

switch to switch config

John,

You are absolutely correct: Catalysts 2950 and 2960 do not support ISL. They support only 802.1Q (which is the only VLAN tagging protocol in use today, anyway). Therefore the command switchport trunk encapsulation is not available because there are no alternatives to choose from.

It's strange that old 2900XL switches supported ISL, as it predated the 802.1Q, then the 2950/2960 do not support it and support only 802.1Q, but 3550/3560/3750 and higher switches stil (or again?) support ISL along with 802.1Q.

Best regards,

Peter

Purple

switch to switch config

  Yeah it would be  nice if they would just standardize and get rid of ISL at this point.

Hall of Fame Super Blue

switch to switch config

It's strange that old 2900XL switches supported ISL, as it predated the 802.1Q, then the 2950/2960 do not support it and support only 802.1Q, but 3550/3560/3750 and higher switches stil (or again?) support ISL along with 802.1Q.

That's not all that's strange.  Guess what standard the old 1900 support:  ISL only.

Community Member

switch to switch config

thank u very very much

243
Views
5
Helpful
5
Replies
CreatePlease to create content