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Configuring Multichassis Link Aggregation on MX Series Routers

On MX Series routers, multichassis link aggregation (MC-LAG) enables a device to form a logical LAG interface with two or more other devices. MC-LAG provides additional benefits over traditional LAG in terms of node-level redundancy, multihoming support, and loop-free Layer 2 network without running the Spanning Tree Protocol (STP). MC-LAG can be configured for virtual private LAN service (VPLS) routing instance, circuit cross-connect (CCC) application, and Layer 2 circuit encapsulation types.

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

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

• Active-standby mode is supported using Link Aggregation Control Protocol (LACP).
• MC-LAG operates only between two chassis.
• Layer 2 circuit functions are supported with ether-ccc and vlan-ccc encapsulation.
• VPLS functions are supported with ether-vpls and vlan-vpls.

Note: Ethernet connectivity fault management (CFM) specified in the IEEE 802.1ag standard for Operation, Administration, and Management (OAM) is not supported on MC-LAG interfaces.

To enable MC-LAG, include the mc-ae statement at the [edit interfaces aeX aggregated-ether-options] hierarchy level along with either the ethernet-bridge, encapsulation ethernet-ccc, encapsulation ethernet-vpls, or flexible-ethernet-services statement at the [edit interfaces aeX] hierarchy level. You also need to configure the lacp statement and the admin-key and system-id statements at the [edit interfaces aeX aggregated-ether-options] hierarchy level:

Note: When you configure the prefer-status-control-active statement, you must also configure the status-control active statement. If you configure the status-control standby statement with the prefer-status-control-active statement, the system issues a warning.

To delete an MC-LAG interface from the configuration, issue the delete interfaces aeX aggregated-ether-options mc-ae command at the [edit] hierarchy level in configuration mode:

To prevent loops in MC-LAG topologies, configure the two edge nodes with the same (STP) virtual root ID using Reverse Layer 2 Gateway Protocol (RL2GP). This root ID should be superior to all bridges in the downstream network because downstream bridges have to be capable of running STP. RL2GP should be configured on both MC-LAG nodes to prevent loops. A potential loop, such as one that can happen due to improper cabling at the core or the access switching layer, or due to a bug in server software, is broken by STP blocking one of the interfaces in the downstream network. Because both MC-LAG nodes are root bridges (virtual), the MC-LAG interface remains in the forwarding state. The downstream bridge receives bridge protocol data units (BPDUs) from both the nodes and thus receives twice the number of BPDUs on its ae interface. If both MC-LAG nodes use the same ae interface name, the STP port number is identical, which reduces the STP load on downstream bridge.

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

   For example:

   [edit interfaces]
user@host# 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 router.
   [edit interfaces]
user@host# set aeX aggregated-ether-options mc-ae chassis-id chassis-id

   For example:

   [edit interfaces]
user@host# 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 for RL2GP at this time.

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

   For example:

   [edit interfaces]
user@host# 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 routers hosting the MC-LAG. If one router is in active mode, the other must be in standby mode.

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

   For example:

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

   For example:

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

   For example:

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

      For example:

      [edit protocols]
user@host# set iccp local-ip-addr 3.3.3.1
   2. (Optional) Configure the IP address of the router and the time during which an ICCP connection must succeed between the routers 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@host# set iccp peer peer-ip-address session-establishment-hold-time seconds

      For example:

      [edit protocols]
user@host# set iccp peer 3.3.3.2 session-establishment-hold-time 50
   3. Configure the minimum interval at which the router must receive a reply from the other router 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@host# set iccp peer peer-ip-address liveness-detection minimum-receive-interval seconds

      For example:

      [edit protocols]
user@host# set iccp peer 3.3.3.2 liveness-detection minimum-receive-interval 60
   4. Configure the minimum transmit interval during which a router must receive a reply from a router with which it has established a BFD session.
      [edit protocols]
user@host# set iccp peer peer-ip-address liveness-detection transmit-interval minimum-interval seconds

      For example:

      [edit protocols]
user@host# set iccp peer 3.3.3.2 liveness-detection transmit-interval minimum-interval 60
8. Configure a multichassis protection link between the routers.
   [edit]
user@host# set multi-chassis multi-chassis-protection peer-ip-address interface interface-name

   For example:

   [edit protocols]
user@host# set multi-chassis multi-chassis-protection 3.3.3.1 interface ae0
9. Enable Rapid Spanning Tree Protocol (RSTP).
   [edit]
user@host# set protocols rstp interface ae1 mode point-to-point
10. Configure the MC-LAG interfaces as edge ports on both routers.
    user@host# set protocols rstp interface interface-name edge

    For example:

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