802.1Q Trunking between 2950 Switches 1

[robertjo24]

Can you trunk between two 2950 switches, or between a 2950 and a 2924XL switch, with the interfaces forced to 10 MB.

We have a couple locations that are linked with 10MBit converters, and we need to know if we can trunk between them without replacing equipment.

 

[wabob]

You need 100Mb in order to trunk ISL or 802.1q.
You can uplink at 10 Mb as a static access port, though.


Experience is a tough teacher.
The test comes first, the lesson comes later...

 

[jneiberger]

You do not need 100 Mbps interfaces. All you need are two interfaces that support trunking. However, you need to make sure that both switches support the same trunk encapsulation type. Your 2950 may only do 802.1Q, and the 2924XL may only do ISL.

As long as you have a common encapsulation type, the trunk will work regardless of the speed setting.

 

[hunterdw]

http://www.cisco.com/en/US/tech/tk389/tk390/technologies_tech_note09186a008017f86a.shtml

2950s don't do ISL, but do dot1q

if you have the 4meg 2924xl, you get no trunks... only the 8meg and higher...

I am running a dot1q trunk right now across 2950s forced 10meg with converters with no problems.

robertjo24, I would just verify your hardware from the trunking requimrents list above

--DW

 

[robertjo24]

Thanks for all the posts.
I was unaware of the 2924XL requirements for trunking, I appreciate the info.
I will set this up in the lab and try it.

I was always told that trunking had to be 100 MBit or higher. This is good information.

 

[jneiberger]

The speed has nothing to do with it. You're thinking of trunk support in the 2600-series routers. With earlier software releases, the 2610/11 with low speed interfaces could not do trunking; you had to have a 2620/21 or better with high speed interfaces to get trunking.

There are no speed requirements for trunk support.

 

[wabob]

robertjo24,

let us know if the 802.1q trunk worked at 10Mb in the lab.

This might be a learning experience for me, too.

Experience is a tough teacher.
The test comes first, the lesson comes later...

 

[robertjo24]

*** Test Update ***

I linked two 2950 switches together with 10Base fiber converters, and programmed the interfaces to trunk with auto speed and auto duplex.
I loaded both switches with our standard configs.
I was able to pass all VTP information.
Traffic on all VLANS communicated properly.
No errors on the trunked interfaces.
New VLANs propagated properly.
Deletion of VLANs propagated properly.

All in all, the switches seem to operate properly. I would imagine that there could be some congestion issues if we were to try to send allot of data over the 10Base link, but in a pinch it is nice to know this works.

 

[jneiberger]

As you've discovered, speed is irrelevant. It simply doesn't matter. You could have a 10 Mbps half duplex trunk, although I don't know why you'd want to.

 

[voltron1011]

robertjo24, thanks for keeping everyone updated.