MLAG configuration

[Sulaiman_Al_Dar]

Hi,
im having a virtual lab, where i try to practice MLAG, the topology is as in the diagram

now i have a problem and some questions regarding MLAGmy problem that MLAG doesnt come up,
i have followed the following on both EXOS1 and EXOS2 switches
EXOS1
configure vlan default delete ports all
configure vr VR-Default delete ports 1-7
configure vr VR-Default add ports 1-7
configure vlan default delete ports 1-7
create vlan "ISC-VLAN"
configure vlan ISC-VLAN tag 10
create vlan "VLAN20"
configure vlan VLAN20 tag 20
enable sharing 3 grouping 3-4 algorithm roundRobin-based lacp
configure vlan ISC-VLAN add ports 3 tagged
configure vlan VLAN20 add ports 3 tagged
configure vlan ISC-VLAN ipaddress 1.1.1.1 255.255.255.252
configure vlan VLAN20 ipaddress 10.1.20.2 255.255.255.0
enable ipforwarding vlan VLAN20

create mlag peer "core"
configure mlag peer "core" ipaddress 1.1.1.2 vr VR-Default

EXOS2
configure vlan default delete ports all
configure vr VR-Default delete ports 1-7
configure vr VR-Default add ports 1-7
configure vlan default delete ports 1-7
create vlan "ISC-VLAN"
configure vlan ISC-VLAN tag 10
create vlan "VLAN20"
configure vlan VLAN20 tag 20
enable sharing 3 grouping 3-4 algorithm roundRobin-based lacp
configure vlan ISC-VLAN add ports 3 tagged
configure vlan ISC-VLAN ipaddress 1.1.1.2 255.255.255.252
configure vlan VLAN20 ipaddress 10.1.20.3 255.255.255.0
enable ipforwarding vlan VLAN20

create mlag peer "core"
configure mlag peer "core" ipaddress 1.1.1.1 vr VR-Default

Where's the output of show mlag peer on EXOS1
* EXOS01.131 # show mlag peer
Multi-switch Link Aggregation Peers:

MLAG Peer : core
VLAN : ISC-VLAN Virtual Router : VR-Default
Local IP Address : 1.1.1.1 Peer IP Address : 1.1.1.2
MLAG ports : 0 Tx-Interval : 1000 ms
Checkpoint Status : Down Peer Tx-Interval : 0 ms
Rx-Hellos : 0 Tx-Hellos : 120768
Rx-Checkpoint Msgs: 0 Tx-Checkpoint Msgs: 0
Rx-Hello Errors : 0 Tx-Hello Errors : 863
Hello Timeouts : 0 Checkpoint Errors : 0
Up Time : N/A Peer Conn.Failures: 0
Local MAC : 50:00:00:03:00:00 Peer MAC : None
Config'd LACP MAC : None Current LACP MAC : 50:00:00:03:00:00
Authentication : None


Alternate path information: None
and from EXOS2
EXOS02.42 # show mlag peer
Multi-switch Link Aggregation Peers:

MLAG Peer : core
VLAN : ISC-VLAN Virtual Router : VR-Default
Local IP Address : 1.1.1.2 Peer IP Address : 1.1.1.1
MLAG ports : 0 Tx-Interval : 1000 ms
Checkpoint Status : Down Peer Tx-Interval : 0 ms
Rx-Hellos : 0 Tx-Hellos : 118591
Rx-Checkpoint Msgs: 0 Tx-Checkpoint Msgs: 0
Rx-Hello Errors : 0 Tx-Hello Errors : 1253
Hello Timeouts : 0 Checkpoint Errors : 0
Up Time : N/A Peer Conn.Failures: 0
Local MAC : 50:00:00:04:00:00 Peer MAC : None
Config'd LACP MAC : None Current LACP MAC : 50:00:00:04:00:00
Authentication : None

Alternate path information: Nonejudging from the output i think that the Hello is not happening between the peers.

can someone advice what am I doing wrong.

also
do we need to tag all VLANs (in this case VLAN 20 ) on ISC Ports? if not, how would the failover happen.
Thanks
Sulaiman

[Eric_Burke]

In my experience, when you're using LACP on the downstream ports, you still need to create a "sharing" group on each switch containing just one member (the one from the local switch). It's a little weird, but it seems to work.

[Tomasz]

Hi Sulaiman,

There is one thing for sure I would add to your config on both sides:
enable mlag port 1 peer core id 1So you specify that your downlink port (no. 1 here) is to be considered as an element of a multi-switch terminated lag with ID of 1, where this ID has to be the same on both switches for that particular MLAG link.

If you had this command, and there was such amount of hellos transmitted and none received, I would take a look at VLAN id (both sides the same), tagging (both sides the same) and if the port is enabled and link connected.

You didn't add VLAN20 to your port 3 on EXOS2 by the way, and to any other ports that have to share this data VLAN.

As on each port, on your ISC you could have some single untagged VLAN, but I think it's better to have clear picture with only tagged VLANs everywhere except access ports. And if you ask, do we need to span all data VLANs across peer-peer connection, the answer is yes. If MLAG peers have to pretend being a single device from a downstream device perspective, they should be able to pass those VLANs' between them in case of unicast traffic.

On how the failover works, you can read thoroughly in EXOS User Guide, it's a really nice lecture not only for this topic. 🙂
https://documentation.extremenetworks.com/exos_22.5/EXOS_User_Guide_22_5.pdf
In brief:
- MLAG switches prevent broadcast, multicast and unknown unicast coming from a downstream device to their peer, without that we would have a broadcast storm;
- if single peer link/lag fails, blocking filter is taken down.

Hope that helps,
Tomasz