Mlag configuration and isc link

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Hello,
i'm going to configure an MLAG between two BD8806 and two cisco fiber channel switch.

At finally i will have something like this:


Actually the two BD are interconnected with two interface 10gb in lacp static. 

Can i use this link to perform the ISC? 
In this link i have a lot of vlan and STP per vlan stp, it's a problem? I need to create a stpd for ISC too? 

I have read that in the ISC link i should not have any STP... 

I need to perform a dedicated link for ISC?? 


Thank you,

Gabriele.
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Gabriele Stella

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Posted 2 years ago

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Edward Tsui, Employee

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Yes, surely you can use those two 10G links to be ISC. You need to create a dedicated VLAN on those 10G(In LAG) to be ISC and get rid of any STP as you don't need STP in MLAG design
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Gabriele Stella

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Ok, so nothing happens if i create a new dedicated vlan without STP in this link with other STP existent? Because my fear its if this can create a loop? In theory not... 

I was thinking to do this configuration :
CORE A

create vlan isc
configure vlan isc tag 10
configure vlan isc add port 3:1 tagged
configure vlan isc ipaddress 10.10.10.1/30

create mlag peer core_b 
configure mlag peer core_b ipaddress 10.10.10.2 

CORE B 
create vlan isc
configure vlan isc tag 10
configure vlan isc add port 3:1 tagged
configure vlan isc ipaddress 10.10.10.2/30

create mlag peer core_a 
configure mlag peer core_a ipaddress 10.10.10.1

Thanks,

Gabriele. 
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Edward Tsui, Employee

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ISC only exists on both core switches and on the inter-link. After you create the MLAG peer, make sure it is working properly before you add other member VLANs on both core switches and cisco.

I don't see any issue for your configuration but If you still worry about it, you may try it in lab first before implement to production.
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Gabriele Stella

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So, i don't need a new dedicated link only for ISC vlan.. 
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Patrick Voss, Alum

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Gabriele,

An ISC is needed in order for MLAG to function properly. I believe what Edward is trying to say is you do not need to worry about a loop on the ISC VLAN because you are only adding one port on BD1 and one port on BD2. STP needs to be removed so it does not block the ISC. By design the two MLAG peers and the MLAG clients (aka the cisco switches) will prevent a loop from happening. If you have other switches that will not be participating in MLAG but will be connected to one of the MLAG peers you will need to worry about loops on those devices only.
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Gabriele Stella

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3 weeks ago, i was configuring this mlag and when prompt the command

#create mlag peer core_b
#configure mlag peer core_b ipaddress 10.10.10.2

I had a recalculation of STP.... 
I don't know why.. 
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Edward Tsui, Employee

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Did you create a new VLAN for ISC or reused existing VLAN for ISC? If you created a new VLAN for ISC and you see recalculation occurred, you may have enable auto-bind in STP configuration. Check the STP configuration to confirm.
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David Choi, Employee

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Hi Gabriele,

As soon as creating mlag peer on an EXOS switch (even without having any MLAG ports), MAC learning mode of all ports in the switch will be changed to the SW mac learning mode so causing its FDB table to be flushed.
I think that is the reason of the recalculation of STP in your case and there might be service impact on clients continues until the fdb and associated arp tables are fully learned and populated.
This is an expected behavior on enabling MLAG peer, not a SW defect.

You should be cautious when creating MLAG peer in production.