Solved: Do ISL trunking supports Native vlan?

mahesh18 · ‎09-09-2010

Hi all,

i know 802.1q trunking supports native lan but need to make sure that if ISL trunking supports native vlan or not?

thanks

mahesh

Giuseppe Larosa · ‎09-09-2010

Hello Mahesh,

ISL has no native vlan concept because it places the whole ethernet frame in the payload of an ISL frame

native Vlan is an 802.1Q specfic feature/concept

Hope to help

Giuseppe

View solution in original post

Jon Marshall · ‎09-09-2010

Mahesh

Just to add to Giuseppe's post -

ISL is Cisco proprietary unlike 802.1q. Because of this ISL does not need a native vlan because by definition you would need to have an all cisco network if you wanted to run ISL on your switches. So every switch would be capable of supporting PVST (Per vlan spanning tree). PVST is Cisco proprietary as well.

802.1q is an IEEE standard and because of this it needs to interoperate with switches that may not run PVST and hence the need for the native vlan ie. the vlan that is not tagged on a trunk link.

Jon

View solution in original post

Giuseppe Larosa · ‎09-09-2010

Hello Mahesh,

ISL has no native vlan concept because it places the whole ethernet frame in the payload of an ISL frame

native Vlan is an 802.1Q specfic feature/concept

Hope to help

Giuseppe

mahesh18 · ‎09-10-2010

Hi Jon and guislar,

Many thanks for reply

Mahesh

Jon Marshall · ‎09-09-2010

Mahesh

Just to add to Giuseppe's post -

ISL is Cisco proprietary unlike 802.1q. Because of this ISL does not need a native vlan because by definition you would need to have an all cisco network if you wanted to run ISL on your switches. So every switch would be capable of supporting PVST (Per vlan spanning tree). PVST is Cisco proprietary as well.

802.1q is an IEEE standard and because of this it needs to interoperate with switches that may not run PVST and hence the need for the native vlan ie. the vlan that is not tagged on a trunk link.

Jon