3.16. Configuring MLAG

Overview

Function Introduction

High availability topologies typically provide redundancy protection at the expense of oversubscription by connecting top-of-rack (TOR) switches and servers to dual aggregation switches. In these topologies, Spanning Tree Protocol prevents network loops by blocking half of the links to the aggregation switches. This reduces the available bandwidth by 50%.

Deploying MLAG removes oversubscription by configuring an MLAG link between two aggregation switches to create a single logical switching instance that utilizes all connections to the switches. Interfaces on both devices participate in a distributed port channel, enabling all active paths to carry data traffic while maintaining the integrity of the Spanning Tree topology.

MLAG provides these benefits:

  • Provides higher bandwidth links as network traffic increases.

  • Utilizes bandwidth more efficiently with fewer uplinks blocked by STP.

  • Connects to other switches and servers by static LAG or LACP without other proprietary protocols.

  • Supports active-active Layer-2 redundancy

Principle Description

N/A

Configuration

image

Fig. 3.23 MLAG

The configurations of Switch1-Switch2 are as below. The configurations of these 2 Switches are same if there is no special description.

step 1 Enter the configure mode

Switch# configure terminal

step 2 Enter the vlan configure mode and create vlan

Switch(config)# vlan database
Switch(config-vlan)# vlan 10,4094
Switch(config-vlan)# exit

step 3 Create a static agg

Switch(config)# interface eth-0-1
Switch(config-if)# static-channel-group 1
Switch(config-if)# no shutdown
Switch(config-if)# exit

step 5 Bind the agg interface to the mlag

Switch(config)# interface agg1
Switch(config-if)# switchport mode trunk
Switch(config-if)# switchport trunk allowed vlan add 10
Switch(config-if)# mlag 1
Switch(config-if)# exit

step 6 Set the attributes of the vlan interface

Switch1

Switch(config)# interface vlan4094
Switch(config-if)# ip address 12.1.1.1/24
Switch(config-if)# exit

Switch2

Switch(config)# interface vlan4094
Switch(config-if)# ip address 12.1.1.2/24
Switch(config-if)# exit

step 7 Enter the mlag configure mode and set the attributes of the mlag

Switch1

Switch(config)# mlag configuration
Switch(config-mlag)# peer-link eth-0-9
Switch(config-mlag)# peer-address 12.1.1.2
Switch(config-mlag)# exit

Switch2

Switch(config)# mlag configuration
Switch(config-mlag)# peer-link eth-0-9
Switch(config-mlag)# peer-address 12.1.1.1
Switch(config-mlag)# end

step 8 Validation

Use the following command to display the information of mlag on Switch1

Switch# show mlag
MLAG configuration:
----------------------------

role : Master
local_sysid : ea90.aecc.cc00
mlag_sysid : ea90.aecc.cc00
peer-link : eth-0-9
peer conf : Yes
Switch# show mlag interface
mlagid local-if local-state remote-state
1 agg1 up up
Switch# show mlag peer
MLAG neighbor is 12.1.1.2, MLAG version 1
MLAG state = Established, up for 00:13:07
Last read 00:00:48, hold time is 240, keepalive interval is 60 seconds
Received 17 messages,Sent 19 messages
Open : received 1, sent 2
KAlive : received 15, sent 16
Fdb sync : received 0, sent 0
Failover : received 0, sent 0
Conf : received 1, sent 1
Connections established 1; dropped 0
Local host: 12.1.1.1, Local port: 61000
Foreign host: 12.1.1.2, Foreign port: 46157
remote_sysid: baa7.8606.8b00
Switch# show mac address-table
Mac Address Table
------------------------------------------ 
(*) - Security Entry

Vlan Mac Address Type Ports
---- --- ------- ---- -----

Use the following command to display the information of mac address table on Switch1:

Switch# show mlag
MLAG configuration:
-----------------

role : Slave
local_sysid : baa7.8606.8b00
mlag_sysid : ea90.aecc.cc00
peer-link : eth-0-9
peer conf : Yes
Switch# show mlag interface
mlagid local-if local-state remote-state
1 agg1 up up
Switch# show mlag peer
MLAG neighbor is 12.1.1.1, MLAG version 1
MLAG state = Established, up for 00:14:29
Last read 00:00:48, hold time is 240, keepalive interval is 60 seconds
Received 19 messages,Sent 19 messages
Open : received 1, sent 1
KAlive : received 17, sent 17
Fdb sync : received 0, sent 0
Failover : received 0, sent 0
Conf : received 1, sent 1
Connections established 1; dropped 0
Local host: 12.1.1.2, Local port: 46157
Foreign host: 12.1.1.1, Foreign port: 61000
remote_sysid: ea90.aecc.cc00

Use the following command to display the information of mlag on Switch2:

Switch# show mac address-table
Mac Address Table
-------------------------------------------
(*) - Security Entry

Vlan Mac Address Type Ports
---------------------------

Application cases

N/A