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Configuring Multichassis Link Aggregation

Note: Multichassis link aggregation (MC-LAG) is supported on QFX3500 and QFX3600 standalone switches running the original CLI, and on QFX5100 switches running Enhanced Layer 2 Software.

Multichassis link aggregation groups (MC-LAGs) enable a client device to form a logical LAG interface between two switches. An MC-LAG provides redundancy and load balancing between the two switches, multihoming support, and a loop-free Layer 2 network without running the Spanning Tree Protocol (STP).

The MC-LAG switches use the Inter-Chassis Control Protocol (ICCP) to exchange the control information between two MC-LAG switches.

On one end of an MC-LAG is an MC-LAG client device, such as a server, that has one or more physical links in a link aggregation group (LAG). This client device does not need to detect the MC-LAG. On the other side of MC-LAG are two MC-LAG switches. Each of the switches has one or more physical links connected to a single client device. The switches coordinate with each other to ensure that data traffic is forwarded properly.

Note: An interface with an already configured IP address cannot form part of the aggregated Ethernet interface or multichassis aggregated Ethernet interface group.

1. Specify the same multichassis aggregated Ethernet identification number for the MC-LAG that the aggregated Ethernet interface belongs to on each switch.
   [edit interfaces]
user@switch# set aeX aggregated-ether-options mc-ae mc-ae-id number

   For example:

   [edit interfaces]
user@switch# set ae1 aggregated-ether-options mc-ae mc-ae-id 3
2. Specify a unique chassis ID for the MC-LAG that the aggregated Ethernet interface belongs to on each switch.
   [edit interfaces]
user@switch# set aeX aggregated-ether-options mc-ae chassis-id number

   For example:

   [edit interfaces]
user@switch# set ae1 aggregated-ether-options mc-ae chassis-id 0
3. Specify the mode of the MC-LAG the aggregated Ethernet interface belongs to.

   Note: Only active-active mode is supported at this time.

   [edit interfaces]
user@switch# set aeX aggregated-ether-options mc-ae mode mode

   For example:

   [edit interfaces]
user@switch# set ae1 aggregated-ether-options mc-ae mode active-active
4. Specify whether the aggregated Ethernet interface participating in the MC-LAG is primary or secondary.

   Primary is active, and secondary is standby.

   Note: You must configure status control on both switches hosting the MC-LAG. If one switch is in active mode, the other must be in standby mode.

   [edit interfaces]
user@switch# set aeX aggregated-ether-options mc-ae status-control (active | standby)

   For example:

   [edit interfaces]
user@switch# set ae1 aggregated-ether-options mc-ae status-control active
5. Specify the same LACP system ID on each switch.
   [edit interfaces]
user@switch# set aeX aggregated-ether-options lacp system-id mac-address

   For example:

   [edit interfaces]
user@switch# set ae1 aggregated-ether-options lacp system-id 00:01:02:03:04:05
6. Specify the same LACP administration key on each switch.
   [edit interfaces]
user@switch# set aeX aggregated-ether-options lacp admin-key number

   For example:

   [edit interfaces]
user@switch# set ae1 aggregated-ether-options lacp admin-key 3
7. Configure ICCP by doing the following on each switch hosting the MC-LAG:
   1. Configure the local IP address to be used by all switches hosting the MC-LAG.
      [edit protocols]
user@switch# set iccp local-ip-addr local-ip-address

      For example:

      [edit protocols]
user@switch# set iccp local-ip-addr 3.3.3.1
   2. (Optional) Configure the IP address of the switch and the time during which an ICCP connection must succeed between the switches hosting the MC-LAG.

      Configuring session establishment hold time helps to establish a faster ICCP connection . The recommended value is 50 seconds.

      [edit protocols]
user@switch# set iccp peer peer-ip-address session-establishment-hold-time seconds

      For example:

      [edit protocols]
user@switch# set iccp peer 3.3.3.2 session-establishment-hold-time 50
   3. (Optional) Configure the IP address to be used for backup liveness detection.

      Note: By default, backup liveness detection is not enabled. Configure backup liveness detection if you require minimal traffic loss during a reboot. Backup liveness detection helps achieve sub-second traffic loss during an MC-LAG reboot.

      [edit protocols]
user@switch# set iccp peer peer-ip-address backup-liveness-detection backup-peer-ip ip-address

      For example:

      [edit protocols]
user@switch# set iccp peer 3.3.3.2 backup-liveness-detection backup-peer-ip 10.207.64.232
   4. Configure the minimum interval at which the switch must receive a reply from the other switch with which it has established a Bidirectional Forwarding Detection (BFD) session.

      Note: Configuring the minimum receive interval is required to enable BFD.

      [edit protocols]
user@switch# set iccp peer peer-ip-address liveness-detection minimum-receive-interval seconds

      For example:

      [edit protocols]
user@switch# set iccppeer 3.3.3.2 liveness-detection minimum-receive-interval 1000
   5. Configure the minimum transmit interval during which a switch must receive a reply from a switch with which it has established a BFD session.
      [edit protocols]
user@switch# set iccp peer peer-ip-address liveness-detection transmit-interval minimum-interval seconds

      For example:

      [edit protocols]
user@switch# set iccp peer 3.3.3.2 liveness-detection transmit-interval minimum-interval 1000
8. Configure a multichassis protection link between the switches.
   [edit]
user@switch# set multi-chassis multi-chassis-protection peer-ip-address interface interface-name

   For example:

   [edit protocols]
user@switch# set multi-chassis multi-chassis-protection 3.3.3.1 interface ae0
9. If you are using ELS, configure the service-id on both switches.

   The service-id must be the same number on both switches.

   [edit]
user@switch# set switch-options service-id number

   For example:

   [edit]
user@switch# set switch-options service-id 10
10. Configure the MC-LAG interfaces as edge ports on both switches.
    user@switch# set protocols rstp interface interface-name edge

    For example:

    [edit]
user@switch# set protocols rstp interface ae1 edge
11. Enable BPDU block on all interfaces except for the ICL-PL interfaces on both switches.
    [edit]
user@switch# set protocols rstp bpdu-block-on-edge