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I'm currently having difficulty determining the best way to connect a Dlink DGS-3420-52T switch stack to a IBM B50G switch stack.

I have two IBM B50G switches stacked together, which then connect to our firewall and then out to the internet.

I have 5 D'Link xStack DGS-3420 series switches stacked together in a ring topology. What is the best way to connect these 5 D'Link DGS-3420 series switches to the IBM B50G stack?

Is LACP (Link Aggregation Control Protocol) going to be my best best?

How do I spread the uplink ports across the D'Link stack?

Is trying to connect these two separate stacks together a bad idea in the first place?

Any help at all would be really appreciated.

David Jackson
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  • possible duplicate of [Configuring LACP across a IBM B50G switch stack](http://serverfault.com/questions/501939/configuring-lacp-across-a-ibm-b50g-switch-stack) – Falcon Momot Feb 25 '14 at 09:35
  • The IBM B50G seem to be Brocade switches. Page 490 of the FastIron 7.1 configuration Guide suggests this should be no problem. – Thomas Roes Feb 03 '15 at 15:36

2 Answers2

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I guess your only choice here is LACP, make some port channels between the switches in a way that makes sense in your topology, take consideration of the amount of traffic has to flow trough each of them and avoid creating bottlenecks.

Martino Dino
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  • Thanks a lot for the quick response. As I understand switch stacking, the entire stack is seen as 1 large switch. If I wanted to use LACP I would have to create a lag that spans 8-10 ports on each stack. 8-10 physical Ethernet cables between the two stacks. Is LACP capable of aggregating 8-10 1 Gigabit cat5e cables spanned across both the Dlink stack and the IBM Stack? – David Jackson Apr 10 '13 at 21:51
  • That depends on the switches, I don't have the specs of them right now but it should not pose any problem – Martino Dino Apr 11 '13 at 01:15
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from the reference documentation, it does not look like the D-Link switches would allow you to create LAGs spanning more than one physical switch, "physical" stacking enabled or not.

Since using just a single switch for stack interconnection would introduce a single point of failure, the route to go probably would be to use two uplinks (or uplink trunks) from the B50G / Brocade stack and make it a member in the ring like the "Chassis switch" in this picture: D-Link topology proposal (pic taken from the D-Link data sheet)

To handle loops, either let Spanning Tree disable one of the link trunks or try to make ERPS work in D-Link's stacked configuration (it is claimed to be supported and would give you shorter recovery times than STP/RSTP).

the-wabbit
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