topic Re: Two tier MLAG in ExtremeSwitching (EXOS/Switch Engine)

Two tier MLAG

RobertD1 — Tue, 08 Mar 2022 17:57:33 GMT

Hello,

Below is a link to an article on MLAG two tier design.

How To: Explaining Two-tier MLAG design | Extreme Portal

Example below shows configuration from Top Left MLAG Peer Switch II:

create vlan isc
configure vlan isc tag 20
configure vlan isc add ports 1 tagged
configure vlan isc ipaddress 198.51.100.5/30
create mlag peer top-right
configure mlag peer top-right lacp-mac 22:33:44:55:66:77
configure mlag peer top-right ipaddress 198.51.100.6
enable sharing 2 grouping 2,3 algorithm address-based l3_l4 lacp 
enable mlag port 2 peer top-right id 300

In the bottom two MLAG peers the peer names are "right" and "left". Is the peer name ie "top-right" unique to one of the MLAG peers and cannot be used elsewhere, in other words are the peer names unique? The opposite peer is configured with peer name "top-left".

Can I reuse "left" and "right" in the top MLAG pair if I want to?

Thanks,
Rob

Re: Two tier MLAG

Gabriel_G — Wed, 09 Mar 2022 18:58:22 GMT

Hi Rob,

Yes, the MLAG Peer 'Names' are only locally significant and are purely for human-readability. In fact, I often use the peer name 'Peer', which allows you to use many of the same commands on both MLAG peer switches.

IE, I can use these same command on both MLAG peers:

create mlag peer peer
enable mlag port 1 peer peer id 1

The key things doing the work are the ISC VLAN and IP, not the peer name.

Re: Two tier MLAG

RobertD1 — Wed, 09 Mar 2022 19:08:19 GMT

Good to know, thanks Gabriel!

Re: Two tier MLAG

FredrikB — Mon, 21 Mar 2022 14:56:34 GMT

As a side-note, all examples in the user's guide I have seen (in the past) have shown a full mesh topology. That is not necessary and employing a "straight down" structure can significantly reduce complexity and is (!) supported by Extreme:

Core1 === Core2
| |
Dist1 === Dist2

In summary, you don't need the "diagonal" connections beween Core1 and Dist2 and not between Core2 and Dist1.
Any access switches would (should) be connected redundantly to Dist1 and Dist2 using an MLAG in the dists and a normal LAG in the access.

The benefit is that you need less fibers between the dists and core. The downside is that if you connect devices to the dists with single links, you get a lot of traffic on the ISC link between the dists, which may not be optimal.

B.t.w., using a LAG for ISC is my recommendation (not just a single ISC link) and an "alternate ISC" might be worth considering in some deployments.