VLAN Trunking between switches

[mcvay_mike]

Is VLAN trunking between switches using 802.1Q encapsulated? If so, is it layer 3 or layer 2 encapsulation?

R/Mike

[daniel.bowen]

Trunks between switches normally use 802.1q or ISL encapsulation. ISL is Cisco propritary where as do1q is IEEE standard. VTP, the protocol that is propagated across trunk links to maintain VLAN consistency is layer 2 (if that is what you are asking)

Daniel,

[markedwards_uk]

802.1Q trunks are encapsulated within the ethernet frame at layer 2 using an internal tag this is to allow multivendor support. ISL on the other hand is still at layer 2 but has an external tag which in contrast extends the size of the ethernet frame and makes the method Cisco proprietary. All tagging terminates at router boundaries and does not extend into layer 3.