Creating and Managing Multichassis Link Aggregation Groups (MC-LAGs)
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 Interchassis 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.
You can create MC-LAGs on QFX3500 and QFX3600 Series devices.
To start creating an MC-LAG:
- Click the Build Mode icon
in the Network Director banner. - Select Device Management > Create MC-LAG in the Tasks pane.
The Create MC-LAG wizard opens to the Device Selections page.
- Continue with the section Selecting Devices for the MC-LAG.
This topic includes:
Selecting Devices for the MC-LAG
To select devices for the MC-LAG in the Device Selections page:
- Click Select Devices.
The Select Two Devices for MC-LAG window opens, listing the devices on which you can create an MC-LAG.
- Select two devices from the list.
- Click Done.
The devices appear in the Devices selected for MC-LAG list.
- Click either Next or MC-LAG Settings.
The MC-LAG Settings page opens. Continue with the section Configuring MC-LAG Settings.
Configuring MC-LAG Settings
On the MC-LAG Settings page you configure MC-LAG and ICCP settings for both selected switches. Some MC-LAG and ICCP settings must be coordinated between the two switches, so when you specify such a setting for one switch, that setting is automatically specified for the other switch.
To configure MC-LAG settings:
- Enter settings in the MC-LAG section for both switches.
The MC-LAG settings configure the connection between the client device and the switch. Table 1 describes the fields in this section.
- Enter settings in the ICCP-LAG section for both switches.
The ICCP settings configure the connection between the peer switches in the MC-LAG. Table 2 describes the fields in this section.
- Select the ports for the MC-LAG and the ICCP LAG in the
Port Selection section.
Each selected device has a tab. For each device, move ports between the Available Ports list and the MC-LAG or ICCP-LAG lists using the arrow keys.
- Click the Finish button.
Table 1: MC-LAG Settings
Field | Description |
|---|---|
AE Name | Select the aggregated Ethernet interface to use in the MC-LAG. |
LACP Mode | Select the LACP mode for the MC-LAG. |
Description | Enter a description for the MC-LAG. |
VLAN | Select the same VLAN profile to associate to the aggregated Ethernet (ae) interface on each switch. |
LACP System ID | Specify the same LACP system ID on each switch. |
LACP Admin Key | Specify the same LACP administration key on each switch. |
AE ID | Specify the same multichassis aggregated Ethernet identification number for the MC-LAG that the aggregated Ethernet interface belongs to on each switch. |
Chassis ID | Specify a unique chassis ID for the MC-LAG that the aggregated Ethernet interface belongs to on each switch. |
Control Status | Specify whether the aggregated Ethernet interface participating in the MC-LAG is primary or secondary. Primary is active, and secondary is standby. |
Init Delay Time (seconds) | Specify an initialization delay time, in seconds. |
Table 2: ICCP-LAG Settings
Field | Description |
|---|---|
AE Name | Select the aggregated Ethernet interface to use for the ICCP connection. |
LACP Mode | Select the LACP mode for the ICCP connection. |
Description | Enter a description for the ICCP connection. |
VLAN Name | Enter the name of the VLAN to use for the ICCP connection. |
Vlan ID | Enter the same VLAN ID to use for the ICCP connection on each switch. |
Local IP | Configure the local IP address to be used by all switches hosting the MC-LAG. |
Liveness min. receive interval (ms) | 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. |
Liveness min. transmit interval (ms) | Configure the minimum transmit interval during which a switch must receive a reply from a switch with which it has established a BFD session. |
Session establish hold time (ms) | Configure the time during which an ICCP connection must succeed between the switches hosting the MC-LAG. Configured session establishment hold time results in faster ICCP connection establishment. The recommended value is 50 seconds. |
Managing MC-LAGs
You manage MC-LAGs using the Manage LAG task.
What To Do Next
The configuration changes that you make in the Build mode are not deployed to devices automatically. After you create an MC-LAG, you must deploy it on the switches. You must manually deploy the changes to devices in Deploy mode. For details, see Deploying Configuration to Devices.
 | Tip: Even though MC-LAG configuration is not contained within a profile, you can view the MC-LAGs assigned to a switch by using the View Assigned Profiles task in Build mode. |
