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M-LAG, ISC and standard trunking over same port group

  • 7 January 2014
  • 3 replies

Userlevel 4
Create Date: Apr 19 2012 4:39AM


Trying to get some feedback on following scenario if possible, cheers in advance.

2 summit switches, same model, same XOS, not stacked. I need to multi hone 3 servers (dual port configured as LACP team) into both switches for redundancy/agg so I was going to implement M-LAG. The ISC port for the switch peering are 4 ports grouped together, however, I'd like to be able to use this same port group for standard trunking between the switches for non M-LAG participating VLANS (about 4 or so other vlans only tagged across trunk to increase end user port density). I can't see anything that suggests this not achievable. Anyone have any thoughts on this?

(from Tony_Stevens)

3 replies

Userlevel 4
Create Date: Apr 19 2012 6:05AM

Hey Tony

If I understand you correctly you want to use the ISC for normal data traffic for VLANs that are not part of the MLAG ports. The answer is that yes that should work as a matter of fact if you are not careful you can create a loop on the network.

The ISC is not responsible for blocking traffic unless it is for a MLAG peer port. See below

The ISC blocking filter matches all Layer 2 traffic received on the ISC and blocks transmission to all MLAG ports that have MLAG peer ports in the active state.

Hope that helps
P (from Paul_Russo)
Userlevel 4
Create Date: Apr 19 2012 6:58AM

Thanks, I'm not anticipating high throughput from the non mlag and mlag vlans over the ISC/trunk and the non mlag vlans will only have connecting devices with one nic so it's an either/or into switch 1 or 2, can't see how a loop can be created so I'll run with the idea and if it drops out on me I'll post back


(from Tony_Stevens)
Userlevel 4
Create Date: May 11 2012 3:01AM

Hi Tony,

I have a production setup similar to what you describe, so this is definately achievable.

Best regards


(from Kenneth_Oestrup)