Link aggregation is the process of creating a virtual interface (bundle), then adding two or more physical interfaces to the bundle. The virtual interface will have the combined data-carrying capacity of all participating links in the bundle. It is similar to etherchannel bundling created on switches. In this demonstration, I will share with us on how to bundle three links between two Cisco ASR 9010 routers to give a link capacity of 3Gbps.
Network Topology
From the network diagram above, we need to bundle the links between RouterA and RouterB to give a link with combined capacity of the three links between both routers. The individual links are 1Gigabit per second each. Our goal is to achieve a link with a data-carrying capacity of 3Gigabit per second between both routers.
Implementation
On RouterA
First, create the bundle interface.
RouterA(config)#interface Bundle-Ether1
RouterA(config-if)# description bundle_to_RouterB
RouterA(config-if)# mtu 9216
RouterA(config-if)# bundle minimum-active links 2
RouterA(config-if)# load interval 30
Then, add interfaces to the bundle.
RouterA(config)# interface GigabitEthernet0/0/0
RouterA(config-if)# description bundle_1_link_1
RouterA(config-if)# bundle id 1 mode active
RouterA(config-if)# load interval 30
RouterA(config-if)# exit
RouterA(config)# interface GigabitEthernet0/0/1
RouterA(config-if)# description bundle_2_link_1
RouterA(config-if)# bundle id 1 mode active
RouterA(config-if)# load interval 30
RouterA(config-if)# exit
RouterA(config)# interface GigabitEthernet0/0/2
RouterA(config-if)# description bundle_3_link_1
RouterA(config-if)# bundle id 1 mode active
RouterA(config-if)# load interval 30
RouterA(config-if)# exit
The minimun active interfaces needed for the bundle to stay up is 2. This means that as long as two physical interfaces are up on this router, the bundle will be up, provided the other end on routerB is active. The active mode used here tells the interface to actively send out Link Aggregation Control Protocol (LACP)
Repeat the steps on RouterB, making sure the right interfaces are selected and added to the bundle.
Verification
To verify bundle status, use the commands show bundle bundle-Ether 1, show bundle status , or show bundle trace, from the privilege mode.