Best practices for shared MAC on MLAG peers?

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Creating an MLAG between two 440-G2's. The ISC will be an LACP of ports 15 and 16 and if I understand it, this LACP link must have a static MAC assigned on both sides of the ISC (on each peer). Is there a recommendation in terms of the MAC to use (do you just make one up)?

Also, mostly out of curiosity - there's a note about downstream LACP switches (one port to each peer) that discusses ensuring that the MLAG ports (ISC LAG) be configured as LACP too (which I'm doing). It reads as though this is a required config (I can't use a single 10Gb ISC connection). What's the reason? Is it because of the shared MAC issue too?  Thanks!
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Eric Burke

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Posted 3 months ago

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Brad Parker, Technical Support Engineer

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Hi Eric,

Use the command

configure mlag peer <peer_name> lacp-mac <mac_address>
to configure the mac address to use. I would heavily advise using one of the mac addresses found on one of the switches in a "show switch" output.

Regarding the second note, static LAGs don't NEED to be configured, but static LAGs aren't often standardized, so there can be differences in assumptions made. LACP is an industry standard protocol, therefore more likely to have agreed upon assumptions. LACP would be required to be configured for dynamic LAGs due to the exchange of LACPDUs.
ThanksBrad
(Edited)
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Eric Burke

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Thanks Brad. So to confirm, the shared mac on each mlag lacp/isc shared port will be the mac of one of the two core 440's. Same on both sides of the link. I'm assuming l3/l4 both there and on the downstream 440's (lacp with one port to each mlag core) will provide the most balanced lacp use?
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Eric Burke

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Okay, so after a little more digging I have another question about this. The KB shows that this command is in support of MLAG ports (ie: the downstream connections to the MLAG pair) using LACP (like a switch with an LACP split between MLAG peers). In one of the KB docs, the command simply says "configure mlag peer <peer_name> mac <mac_address>" but in another (as above) it shows "lacp-mac" as the argument.

Since MLAG Peer (ISC) and MLAG Port (downstream LACP) don't seem related, I'm a little confused. Does this command get executed on each peer (naming the other) like other MLAG peer commands? The document references the LACP actor address, but I'm not fully understanding how these relate...  Here's my config (two single units at core, stack of 2 remote switches):

SW1
en sharing 1:15 group 1:15,1:16 algorithm address-based L3_L4 lacp
create vlan v4001-isc
config vlan v4001-isc tag 4001
config vlan v4001-isc add port 1:15 tag
config vlan v4001-isc ipaddress 1.1.1.1/30

create mlag peer "core-sw2"
config mlag peer “core-sw2” ipaddress 1.1.1.2
config mlag peer "core-sw2" lacp_mac 02:04:96:a2:02:b4


SW2
en sharing 1:15 group 1:15,1:16 algorithm address-based L3_L4 lacp
create vlan v4001-isc
config vlan v4001-isc tag 4001
config vlan v4001-isc add port 1:15 tag
config vlan v4001-isc ipaddress 1.1.1.2/30

create mlag peer "core-sw1"
config mlag peer “core-sw1” ipaddress 1.1.1.1
config mlag peer "core-sw1" lacp_mac 02:04:96:a2:02:b4

LACP from remote switch to both core switches (both cores 1:1 remote 1:1/2:1)
  REMOTE SW1
  en sharing 1:1 group 1:1,2:1 algorithm address-based L3_L4 lacp
  config vlan... port 1:1 tag
  
  MLAG Port SW1
  en mlag port 1:1 peer "core-sw2” id 1
  
  MLAG Port SW2
  en mlag port 1:1 peer "core-sw1" id 1
  
  
Is that it?
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Ron Huygens, Employee

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You also need to enable LACP on the MLAG ports in SW1 and SW2
  MLAG Port SW1
  en mlag port 1:1 peer "core-sw2” id 1
  en sharing 1:1 group 1:1 algorithm address-based L3_L4 lacp
  
  MLAG Port SW2
  en mlag port 1:1 peer "core-sw1" id 1
  en sharing 1:1 group 1:1 algorithm address-based L3_L4 lacp
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Eric Burke

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Thanks Ron. Missed that. So even though each switch is only singly connected you still need LACP to make the LAG work. I was thinking that somehow the MLAG port definition inherently did that, but then I guess it wouldn't work for different (non LACP) LAG types. Cool and - thanks!
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Eric Burke

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I guess it all boils down to the fact the the ISC is really nothing more than a normal LACP trunk to which the ISC VLAN is connected and across which the peer is defined, along with other VLAN's that are needed to support the "cross-core" LACP connections? Does that pretty much sum it up?
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Ron Huygens, Employee

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That is a correct conclusion.