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Webcast-Catalyst9k
New Member

ISL and DOT1.Q

Can catalsyt support mix and match? I wanna use some ports with ISL and and some with DOT1.Q trunking.  Is it possible or you are bound to use only one for the whole chassis.

6 REPLIES
Cisco Employee

Re: ISL and DOT1.Q

Hello,

You can use a mix of DOT1q or ISL trunks in the switch (except on some where ISL is not supported).

Regards,

NT

VIP Super Bronze

Re: ISL and DOT1.Q

Hi Abbas,

In addition to NT's comments, here are some of the 6500 modules that do not support ISL:

When configuring Layer 2 LAN ports, follow these guidelines and restrictions:

The following switching modules do not support ISL encapsulation:

WS-X6502-10GE

WS-X6548-GE-TX, WS-X6548V-GE-TX, WS-X6548-GE-45AF

WS-X6148-GE-TX, WS-X6148V-GE-TX, WS-X6148-GE-45AF

http://scc.cisco.com/en/US/docs/routers/7600/ios/12.2SXF/configuration/guide/layer2.html

HTH

Reza

Hall of Fame Super Gold

Re: ISL and DOT1.Q

Addition to what was posted, the following model DO NOT support ISL:

2940/2950/2955, 2960/2960S

NOTE:

1900 will support ONLY ISL

New Member

Re: ISL and DOT1.Q

to also add to this remember:

isl does not use a native vlan

if one side isl and the other is dot 1q the link will work you just will get native vlan miss matches on the dot1q side and also may course baby giant frames.

Hall of Fame Super Blue

Re: ISL and DOT1.Q

Scott_O'Brien wrote:

to also add to this remember:

isl does not use a native vlan

if one side isl and the other is dot 1q the link will work you just will get native vlan miss matches on the dot1q side and also may course baby giant frames.

Scott

A switch can use a mixture of 802.1q and ISL encapsulations on trunk links but a trunk link between 2 switches must be the same encapsulation as ISL and 802.1q use very different methods when they add a vlan tag ie.

802.1q inserts a tag into the existing frame

ISL actually encapsulates the frame with a new header

so the 2 switches must agree on the encapsulation being used per trunk link otherwise they will be looking for the vlan information in the wrong place.

Jon

Hall of Fame Super Gold

Re: ISL and DOT1.Q

Aside from what Jon's mentioned (+5), be aware that not all brand will support ISL.

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