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Example: Configuring Multichassis Link Aggregation for Layer 3 Unicast Using VRRP on MX Series Routers

Requirements

This example uses the following hardware and software components:

• Four Juniper Networks MX Series routers
• Junos OS Release 11.2 or later running on all four routers

• Configure aggregated Ethernet interfaces on a router.
• Configure the Link Aggregation Control Protocol (LACP) on aggregated Ethernet interfaces on a router.
• Configure the Virtual Router Redundancy Protocol (VRRP) on a router.

Overview

In this example, you configure an MC-LAG across two routers by including interfaces from both routers in an aggregated Ethernet interface (ae1). To support the MC-LAG, create a second aggregated Ethernet interface (ae0) for the interchassis control link-protection link (ICL-PL). Configure a multichassis protection link for the ICL-PL, Inter-Chassis Control Protocol (ICCP) for the peers hosting the MC-LAG, and Layer 3 connectivity between MC-LAG peers.

Note: Layer 3 connectivity is required for ICCP.

To complete the configuration, enable VRRP by completing the following steps:

1. Create a routed VLAN interface (RVI).
2. Create a VRRP group and assign a virtual IP address that is shared between each router in the VRRP group.
3. Enable a member of a VRRP group to accept all packets destined for the virtual IP address if it is the master in the VRRP group.

Consider a sample topology in which a customer edge router, CE, is connected to two provider edge (PE) routers, PE1 and PE2, respectively. The two PE devices each have a LAG connected to the CE device. The configured mode is active-active, meaning that both PE routers’ LAG ports are active and carrying traffic at the same time. PE1 and PE2 are connected to a single service provider router, P.

In this example, the CE router is not aware that its aggregated Ethernet links are connected to two separate PE devices. The two PE devices each have a LAG connected to the CE device. The configured mode is active-active, meaning that both PE routers’ LAG ports are active and carrying traffic at the same time.

In Figure 1, from the perspective of Router CE, all four ports belonging to a LAG are connected to a single service provider device. Because the configured mode is active-active, all four ports are active, and the CE device load-balances the traffic to the peering PE devices. On the PE routers, a regular LAG is configured facing the CE device.

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 an MC-LAG are two MC-LAG routers. Each of the routers has one or more physical links connected to a single client device. The routers coordinate with each other to ensure that data traffic is forwarded properly.

ICCP messages are sent between the two PE devices. In this example, you configure an MC-LAG across two routers, consisting of two aggregated Ethernet interfaces, an interchassis control link-protection link (ICL-PL), multichassis protection link for the ICL-PL, and ICCP for the peers hosting the MC-LAG.

Topology Diagram

Figure 1 shows the topology used in this example.

Figure 1: MC-LAG Active-Active on MX Series Routers

Configuring the PE Routers

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level , and then enter commit from configuration mode.

Router PE1

Step-by-Step Procedure

1. Specify the number of aggregated Ethernet interfaces to be created.

   [edit chassis]user@PE1# set aggregated-devices ethernet device-count 5

2. Specify the members to be included within the aggregated Ethernet bundles.

   [edit interfaces]user@PE1# set ge-1/0/1 gigether-options 802.3ad ae1user@PE1# set ge-1/0/6 gigether-options 802.3ad ae0

3. Configure the interfaces that connect to senders or receivers, the ICL interfaces, and the ICCP interfaces.

   [edit interfaces]user@PE1# set ge-1/1/1 flexible-vlan-tagginguser@PE1# set ge-1/1/1 encapsulation flexible-ethernet-servicesuser@PE1# set ge-1/1/1 unit 0 encapsulation vlan-bridgeuser@PE1# set ge-1/1/1 unit 0 vlan-id-range 100-110user@PE1# set ge-1/1/4 flexible-vlan-tagginguser@PE1# set ge-1/1/4 encapsulation flexible-ethernet-servicesuser@PE1# set ge-1/1/4 unit 0 encapsulation vlan-bridgeuser@PE1# set ge-1/1/4 unit 0 vlan-id-range 100-110user@PE1# set ge-1/0/2 unit 0 family inet address 100.100.100.1/30

4. Configure parameters on the aggregated Ethernet bundles.

   [edit interfaces ae0]user@PE1# set flexible-vlan-tagginguser@PE1# set encapsulation flexible-ethernet-servicesuser@PE1# set unit 0 encapsulation vlan-bridgeuser@PE1# set unit 0 vlan-id-range 100-110user@PE1# set unit 0 multi-chassis-protection 100.100.100.2 interface ge-1/1/4.0
   [edit interfaces ae1]user@PE1# set flexible-vlan-tagginguser@PE1# set encapsulation flexible-ethernet-servicesuser@PE1# set unit 0 encapsulation vlan-bridgeuser@PE1# set unit 0 vlan-id-range 100-110user@PE1# set unit 0 multi-chassis-protection 100.100.100.2 interface ge-1/1/4.0

5. Configure LACP on the aggregated Ethernet bundles.

   [edit interfaces ae0 aggregated-ether-options]user@PE1# set lacp activeuser@PE1# set lacp system-priority 100user@PE1# set lacp system-id 00:00:00:00:00:05user@PE1# set lacp admin-key 1
   [edit interfaces ae1 aggregated-ether-options]user@PE1# set lacp activeuser@PE1# set lacp system-priority 100user@PE1# set lacp system-id 00:00:00:00:00:05user@PE1# set lacp admin-key 1

6. Configure the MC-LAG interfaces.

   [edit interfaces ae0 aggregated-ether-options]user@PE1# set mc-ae mc-ae-id 5user@PE1# set mc-ae redundancy-group 10user@PE1# set mc-ae chassis-id 1user@PE1# set mc-ae mode active-activeuser@PE1# set mc-ae status-control active
   [edit interfaces ae1 aggregated-ether-options]user@PE1# set mc-ae mc-ae-id 10user@PE1# set mc-ae redundancy-group 10user@PE1# set mc-ae chassis-id 1user@PE1# set mc-ae mode active-activeuser@PE1# set mc-ae status-control active
   The multichassis aggregated Ethernet identification number (mc-ae-id) specifies which link aggregation group the aggregated Ethernet interface belongs to. The ae0 interfaces on Router PE1 and Router PE2 are configured with mc-ae-id 5. The ae1 interfaces on Router PE1 and Router PE2 are configured with mc-ae-id 10. (To refer to the configuration on Router PE2, see Router PE2)

   The redundancy-group 10 statement is used by ICCP to associate multiple chassis that perform similar redundancy functions and to establish a communication channel so that applications on peering chassis can send messages to each other. The ae0 and ae1 interfaces on Router PE1 and Router PE2 are configured with the same redundancy group, redundancy-group 10.

   The chassis-id statement is used by LACP for calculating the port number of the MC-LAG's physical member links. Router PE1 uses chassid-id 1 to identify both its ae0 and ae1 interfaces. Router PE2 (as shown in Router PE2) uses chassis-id 0 to identify both its ae0 and ae1 interfaces.

   The mode statement indicates whether an MC-LAG is in active-standby mode or active-active mode. Chassis that are in the same group must be in the same mode.

7. Configure a domain that includes the set of logical ports.

   [edit bridge-domains bd0]user@PE1# set domain-type bridgeuser@PE1# set vlan-id alluser@PE1# set service-id 20user@PE1# set interface ae0.0user@PE1# set interface ae1.0user@PE1# set interface ge-1/0/3.0user@PE1# set interface ge-1/1/1.0user@PE1# set interface ge-1/1/4.0
   The ports within a bridge domain share the same flooding or broadcast characteristics in order to perform Layer 2 bridging.

   The bridge-level service-id statement is required to link related bridge domains across peers (in this case Router PE1 and Router PE2), and should be configured with the same value.

8. Configure ICCP parameters.

   [edit protocols iccp]user@PE1# set local-ip-addr 100.100.100.1user@PE1# set peer 100.100.100.2 redundancy-group-id-list 10user@PE1# set peer 100.100.100.2 liveness-detection minimum-interval 1000

9. Configure the service ID at the global level.

   [edit switch-options]user@PE1# set service-id 10
   You must configure the same unique network-wide configuration for a service in the set of PE routers providing the service. This service ID is required if the multichassis aggregated Ethernet interfaces are part of a bridge domain.

Step-by-Step Procedure

1. Enable VRRP on the MC-LAG on PE1 :
   • Create a routed VLAN interface (RVI), assign a virtual IP address that is shared between each router in the VRRP group, and assign an individual IP address for each router in the VRRP group:
     [edit interfaces]
user@PE1# set vlan unit 100 family inet address 100.1.1.11/24 vrrp-group 1 virtual-address 100.1.1.1
   • Assign the priority for each router in the VRRP group:

     Note: The router configured with the highest priority is the master.

     [edit interfaces]
user@PE1# set vlan unit 100 family inet address 100.1.1.11/24 vrrp-group 1 priority 200
   • Enable the router to accept all packets destined for the virtual IP address if it is the master in the VRRP group:
     [edit interfaces]
user@PE1# set vlan unit 100 family inet address 100.1.1.11/24 vrrp-group 1 accept-data

Step-by-Step Procedure

1. Enable RSTP globally on all interfaces.
   [edit]
user@PE1# set protocols rstp interface ae1.0 mode point-to-point
2. Configure the MC-LAG interfaces as edge ports .

   Note: The ae1 interface is a downstream interface. This is why RSTP and bpdu-block-on-edge need to be configured.

   [edit]
user@PE1# set protocols rstp interface ae1.0 edge
3. Enable BPDU blocking on all interfaces except for the ICL-PL interfaces .

   Note: The ae1 interface is a downstream interface. This is why RSTP and bpdu-block-on-edge need to be configured.

   [edit]
user@PE1# set protocols rstp bpdu-block-on-edge

Results

From configuration mode, confirm your configuration by entering the show bridge-domains, show chassis, show interfaces, show protocols, and show switch-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Repeat the procedure for Router PE2, using the appropriate interface names and addresses.

Configuring the CE Router

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level , and then enter commit from configuration mode.

Router CE

Step-by-Step Procedure

1. Specify the number of aggregated Ethernet interfaces to be created.

   [edit chassis]user@CE# set aggregated-devices ethernet device-count 2

2. Specify the members to be included within the aggregated Ethernet bundle.

   [edit interfaces]user@CE# set ge-2/0/2 gigether-options 802.3ad ae0user@CE# set ge-2/0/3 gigether-options 802.3ad ae0

3. Configure an interface that connects to senders or receivers.

   [edit interfaces ge-2/1/6]user@CE# set flexible-vlan-tagginguser@CE# set encapsulation flexible-ethernet-servicesuser@CE# set unit 0 encapsulation vlan-bridgeuser@CE# set unit 0 vlan-id-range 100-110

4. Configure parameters on the aggregated Ethernet bundle.

   [edit interfaces ae0]user@CE# set flexible-vlan-tagginguser@CE# set encapsulation flexible-ethernet-servicesuser@CE# set unit 0 encapsulation vlan-bridgeuser@CE# set unit 0 vlan-id-range 100-500

5. Configure LACP on the aggregated Ethernet bundle.

   [edit interfaces ae0 aggregated-ether-options]user@CE# set lacp activeuser@CE# set lacp system-priority 100
   The active statement initiates transmission of LACP packets.

   For the system-priority statement, a smaller value indicates a higher priority. The device with the lower system priority value determines which links between LACP partner devices are active and which are in standby mode for each LACP group. The device on the controlling end of the link uses port priorities to determine which ports are bundled into the aggregated bundle and which ports are put in standby mode. Port priorities on the other device (the noncontrolling end of the link) are ignored.

6. Configure a domain that includes the set of logical ports.

   [edit bridge-domains bd0]user@CE# set domain-type bridgeuser@CE# set vlan-id alluser@CE# set interface ge-2/1/6.0user@CE# set interface ae0.0
   The ports within a bridge domain share the same flooding or broadcast characteristics in order to perform Layer 2 bridging.

Results

From configuration mode, confirm your configuration by entering the show bridge-domains, show chassis, and show interfaces commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Configuring the Provider Router

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level , and then enter commit from configuration mode.

Router P

Step-by-Step Procedure

1. Specify the number of aggregated Ethernet interfaces to be created.

   [edit chassis]user@P# set aggregated-devices ethernet device-count 2

2. Specify the members to be included within the aggregated Ethernet bundle.

   [edit interfaces]user@P# set ge-1/0/5 gigether-options 802.3ad ae1user@P# set ge-1/0/11 gigether-options 802.3ad ae1

3. Configure an interface that connects to senders or receivers.

   [edit interfaces ge-1/1/3]user@P# set flexible-vlan-tagginguser@P# set encapsulation flexible-ethernet-servicesuser@P# set unit 0 encapsulation vlan-bridgeuser@P# set unit 0 vlan-id-range 100-500

4. Configure parameters on the aggregated Ethernet bundle.

   [edit interfaces ae1]user@P# set flexible-vlan-tagginguser@P# set encapsulation flexible-ethernet-servicesuser@P# set unit 0 encapsulation vlan-bridgeuser@P# set unit 0 vlan-id-range 100-110

5. Configure LACP on the aggregated Ethernet bundle.

   [edit interfaces ae1 aggregated-ether-options]user@P# set lacp activeuser@P# set lacp system-priority 100

6. Configure a domain that includes the set of logical ports.

   [edit bridge-domains bd0]user@P# set vlan-id alluser@P# set domain-type bridgeuser@P# set interface ge-1/1/3.0user@P# set interface ae1.0

Results

From configuration mode, confirm your configuration by entering the show bridge-domains, show chassis, and show interfaces commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Verification

• show iccp
• show interfaces ae0
• show interfaces ae1
• show interfaces mc-ae
• show vrrp
• show l2-learning instance extensive

Troubleshooting

Troubleshooting a LAG That Is Down

Problem

The show interfaces terse command shows that the MC-LAG is down.

Solution

Check the following:

1. Verify that there is no configuration mismatch.
2. Verify that all member ports are up.
3. Verify that the MC-LAG is part of family Ethernet switching (Layer 2 LAG).
4. Verify that the MC-LAG member is connected to the correct MC-LAG member at the other end.