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802.10 FDDI Trunking - tough one


I have 5 Cat 5000's with FDDI cards and 2 Cisco 1400 FDDI concentrators - all making up a FDDI ring.

All Ethernet ports are configured with just the native VLAN 1.

Now i need to introduce another VLAN between 2 switches. No big problem here.

Just set vlan 10 for Ethernet and vlan 100 for FDDI, and translate between them.

set vlan 10

set vlan 100 type fddi

set vlan 10 translation 100

set trunk 5/1 on

Question is this - what about the 1400 concentrators. They are not capable of trunking as far as i can tell?

If the traffic i am sending around the FDDI ring is 802.10 packets - will the concentrators recognise that the traffic is for VLAN 10/100 and not assume its for the native VLAN 1?

When it passes through the 1400 - will it lose it's 802.10 tag??

Can anyone help me out or point me towards an answer.

  • Other Network Infrastructure Subjects

Re: 802.10 FDDI Trunking - tough one

Interesting case. I found a document on CCO. You may have found it also:

This document describes how to send tagged frames over FDDI. This is exactly what you want to achieve. Your doubts about 802.10 are unfounded. 802.10 is FDDI, hence this method should be transparent to the medium. You are not sending around frames with a vlan-tag, this tag is translated into an SAID instead. Should work!



New Member

Re: 802.10 FDDI Trunking - tough one

Hi Leo,

Thanks for the reply.

I'm happy that 802.10 will trunk around the FDDI. I'm happy to translate between Ethernet VLAN's and FDDI VLAN's.

From what you are saying and from what i've read - it looks as if it modifies the SAID.

So - does this mean that it still looks like a standard unaltered FDDI frame? Not too sure about this. If it doesn't there is no problem.

If it does - will the 1400 concentrator know what the frame is and just keep forwarding it around the ring.

My guess would be yes it would.



Re: 802.10 FDDI Trunking - tough one

Yes Fergus, I expect that this will work. What is transmitted over FDDI is a standard frame. It's header-contents will not be changed by intermediate nodes.



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