ISL vs 802.1Q

[ikizoo4]

foundamental question...

ISL : support multi protocol like FDDI, TokenRIng, Ethernet,

802.1q : support only Ethenet.

whatelse could it be the differences between them?

Thanks a lot

[pkhatri]

Some more:

ISL:

- Cisco proprietary

- encapsulates the entire ethernet frame using a 26-byte header and a 4-byte trailer

- does not have a concept of a native vlan i.e all frames are tagged

802.1q:

- IEEE standard

- adds a 4-byte tag before after the source address of the frame, and does not encapsulate the frame as such

- traffic in native VLAN is not tagged

Hope that helps - pls do rate the post if it does.

Paresh

[diro]

802.q also adds 802.1p capabilities and thus supporting qos/co

[laurentElens]

ISL:

- support Per Vlan Spanning Tree PVST+

802.1q:

- support Multiple Spanning Tree Protocol MSTP (802.1s) which allows more macromanagement opportunities by the use of internal spanning tree (IST) and regions.

[rwdorman]

ISL is also not supported on some lower end switches, i.e. 2950, 2960, 2940.