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vlans vs trunking

Chris Bullock_1
Frequent Advisor

vlans vs trunking

I have asked a variance of this question before but I am going to ask it another way. At our main office we have a 4108gl with 7 modules, one being the J4893A (mini gbic module) This gives me the following ports B1-B6. My switch has 3 vlans. I have 4 other buildings that I want to connect to this switch. those buildings will have the same vlans and same vlan ids as the 4108. I have the following 1 2824, 1 4160gl, 2 2650s. B1 will be the port that will uplink switch 2824 on port 24 via the fiber port, B2 will uplink the 2650a via its fiber port, B3 will uplink 2650b, B4 will uplink the 4160gl via one of its fiber ports. My question should I trunk these ports. And if I do how will that affect vlans? And if i trunk them how would I do that. I cant seem to find any good documentation on procurve trunking.
6 REPLIES
Les Ligetfalvy
Esteemed Contributor

Re: vlans vs trunking

What do you consider trunking, VLAN trunking (tagging) or link (multiple ports) aggregation, or both?
Chris Bullock_1
Frequent Advisor

Re: vlans vs trunking

I am not sure what I really need, but I have 4 switches and each needs the same 3 vlans. What are my options?
Jonathan Axford
Trusted Contributor

Re: vlans vs trunking

You should use trunking if you are going to use more than one interface to connect each of the other switches. E.g int b1 and b2 will connect to 23 and 24 on the 2824, By using trunking you are combining the 2 interfaces together to create 1 larger virtual interface and also preventing STP from blocking one of the links.
I would recommend tagging the interswitch links in all VLAN's, This will ensure that your Spanning-tree domain gets configured properly, If yu are using it.

Hope this helps,

Jonathan
Where there is a will there is a way...
Chris Bullock_1
Frequent Advisor

Re: vlans vs trunking

I do not have a need to create virtual interfaces. port B1 will be connected to remote switch1, B2 will be connected to remote switchb, B3 will be connected to remote switchc, B4 will be connected to remote switchd. Since there is no redundant connections I do not think i will need to turn on STP since only one port is uplinking each switch.
Les Ligetfalvy
Esteemed Contributor

Re: vlans vs trunking

Well... that's not the answer you gave me when I asked about link aggregation. :(

Sound then like all you need is VLAN tagging.

As for your STP arguement, it does not hold up to scrutiny. The threat of multiple ISLs creating a quantum packet accelerator (AKA BlinkenLights) is less likely than some BDU plugging the same jumper into two drops in his/her office.
Olaf Borowski
Respected Contributor

Re: vlans vs trunking

Chris,
Let me try to shed some light on this:
ProCurve trunking = Link aggregation.
If you want to aggregate links (e.g. increase bandwidth 2 x 1000BaseT link) to create a pipe of 2Gbit.

Tagging:
Let's say you have two switches with Vlan 1, 2, and 3 on both and you want to connect both switches. You could run 3 seperate links between them each carrying one of the above Vlans. As you can see, this doesn't scale very well if you have lots of Vlans.
Solution: Vlan tagging.
You would have one link between the two switches. Without Vlan tagging, the switches wouldn't know what Vlan the packet came from. Solution: On this one link, the packet is tagged with an ID telling the remote switch what Vlan it's from. This scales much better although all three Vlan share the same link.
Hope this helps,

Olaf