# ICR Terms

Table 29 defines terms used in this discussion of ICR.

Table 29: ICR Terminology

Term | Description
--- | ---
ICR cluster | Group of E Series routers participating in interchassis redundancy (ICR) deployment.
ICR interface | Physical interface, for example, gigabitEthernet 3/1/3, on an E Series router on which ICR is enabled. The ICR interface is always tied to a unique router.
ICR partition | A logical group of subscriber interfaces within a single ICR interface. For example, the ICR partition can be a group of S-VLANs configured on a single physical interface. You can create multiple partitions on each ICR interface and configure the number of partitions, as well as assign subscribers to the partition. An ICR partition can be configured as master or backup.
VRRP | Virtual Router Redundancy Protocol. Use VRRP to prevent loss of network connectivity by configuring backup routers. The backup routers maintain network connectivity when the master router fails. You can configure unique VRRP instances to manage each ICR partition.
VSA | Vendor-specific attributes. VSAs are defined by remote-access server vendors to customize how RADIUS works on their servers. VSAs can be used in combination with RADIUS-defined attributes.