LACP connected host --- two tier MLAG --- LACP connected host

  • 24 January 2017
  • 8 replies

Hi all,

we have the following testsetup and i have a question regarding the different ping behavior as shown below... plz have a look and thank you in advance

two tier MALG with two connected LACP Hosts/switches

config as shown below....



8 replies

Userlevel 4
Hello Enrico,
It seems all of ISC ports do not have data vlan "v_test" as tagged.
Can you check again after you assign the ISC ports to the vlan as tagged port on all the switches?

Userlevel 4
I think this article also will be helpful for better understanding.

Please check "Step 5: Add data carrying VLANs." carefully.
Hey Roy,

yep thx, u´re right^^ it´s working now.

I have another question, regarding migrating the hole system from EAPS Domain to this two Tier MLAG design.

- currently we use LACP connected devices or single connected devices

- we want to migrate them Step by Step to the MLAG

e.g.: enable mlag port 3:2 peer isc-test-2 id 71

- is it a problem to run "normal" connected devices without a mlag peer configuration at the edge port, with devices at mlag peer configured edge ports at the same MLAG switch?

Are there any known challenges or best practices to get this done without greater interruptions?

thx in advance!

Userlevel 4
Hello Enrico,

I actually didn't get the assumption that you are saying with "normal connected devices without a mlag peer configuration at the edge port, with devices at mlag peer configured edge ports at the same MLAG switch".
Do you mean by that there's no mlag peer configuration between two dist switches and connect a access switch to both of them? Then it definitely makes a loop.
Can you explain it for better understanding?

Hi Roy,

I have tried to show this in this picture below - we want to migrate the EAPS Setup (BLACK) to the MLAG Setup (RED) without any interruption if possible

1. first we have the EAPS setup (black connections) - some devices are connected with LACP some just have a single connection

2. we want to configure the MLAG setup with ports shutdown - break up the EAPS - and migrate the attached devices step by step to the MLAG

to aviod loops we decided to shudown one port of any LAG/LACP connected device (e.g. the dual-homed Access Switches ) so we just have to add a single connection to the MLAG ports by adding them like this (enable mlag port <> peer isc-test-2 id 71)

so i think we dont run into any problems , if half of the MLAG ports (lsc-test-1 - lsc-test-2) are configured with (enable mlag port <> peer isc-test-2 id 71) and the others without - as long as we ensure that we do not have any LACP dual-homed devices connected to MLAG ports (lsc-test-1 - lsc-test-2) without an enabled mlag port (enable mlag port <> peer isc-test-2 id 71) configuration.


Userlevel 4
Enrico, Sorry for late response.
Yes, I think there should be no issue if you stick to your plan.
ELRP can be helpful to detect a temporary loop just in case.
You can easily be noticed by switch logs if there's any loop.

Hi Roy,

thank you for your help.

ELRP just need to be configured at non MLAG ports, right?


Userlevel 4
I guess there should be no loop based on your scenario, but a loop may produced by mistake on configuration or by edge switches. EXOS user guide introduces some cases and how to prevent it with ELRP egress port disable with MLAG configuration.