Fault tolerance in the switches

I have 5 switches in this scenario:
2 Dell 5424 switches
3 3Com 4226 Switches.

Dell switches are used as core switches which are connected the servers. the 3 3 com switches uplinked and connected to dell switch from different floor. I would like to know, How do we do failover connections for the 3 com switches? I have 2 cables coming from 3 com switches to connect each dell switches. (right now, only one connection is made) What configurations are need on all switches to have a failover/load balancing for the 3 com switches with 2 cables?

Thanks for your help
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aleghartConnect With a Mentor Commented:
If you have 3Com1 going to Dell1 and Dell2 with one cable to each, you get redundancy, but no aggregation for bandwidth.

You need 2 links aggregated from 3Com1 to Dell1 for extra bandwidth.

Then, 2 links aggregated from 3Com1 to Dell2 for a redundant path.
Istvan KalmarHead of IT Security Division Commented:

Please use the latest firmware, and enable STP on all devices, and connect 3COM switches individual 5424 switches.... the STP will be blocking the backup line, and the primary broken it comes up!

Best regards,
BasheerptAuthor Commented:
No need of Trunking or VLAN things? If i need to have aggregated line, this setup will provide it?
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Istvan KalmarHead of IT Security Division Commented:
yes, need, and use same stp the that the sitches compatible... configure all switch PVST, and confiure dor root bridge the DELL the lowest bridge id the root
If you don't trunk the links with some form of link aggregation then Spanning tree will block one and allow the other. If you have multiple VLANs that need to go across the trunks then you need to tag them in each VLAN.
You _can_ aggregate the two ports from 3Com1 to Dell switch.  But this only provides failover if ONE of the physical cables is cut/unplugged or the port goes down.

If Dell1 is uplinked to Dell2 (or even in a stack), if Dell1 goes down...3Com1 is removed from the rest of the LAN.

Failover to Dell2 is necessary to maintain connectivity to the rest of the LAN.

If you need the bandwidth, this means creating a 2-port LAG to Dell1, and another 2-port LAG to Dell2...enabling STP so only one connection is active...then repeating on 3Com2 and 3Com3.

Dell1 can be uplinked to Dell2 or stacked (if possible).
BasheerptAuthor Commented:
Hi Aleghart,
I would like to have more elaboration.
My two Dell switches are already connected together with trunking. (port 23 and 24 on each switch are aggregated).

The 2 cables coming from the 3com (which are aggregated), one goes to Dell 1 (to say Port 9), other goes to Dell 2 (say Port 9). I enable STP on both ports and in the 3Com. In this way, I have redundacy on the links, am I right? In this way, how can i get the benefit of aggregation? In short, the aggregation can be spanned among two different physical switch ports?

Whats the best way i can adopt to have failover and increased bandwidth?

I appreciate your help.
Istvan KalmarHead of IT Security Division Commented:

forget the aggregation on 3com 4226, it is not working properly, I have some customer where it couses loop, forget it!
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