Design Reference

example, they want to access the Internet, data storage, VoIP-PSTN, or call signaling services.
To interconnect VRF instances, you can use an external firewall that supports virtualization,
or use inter-VRF forwarding for specific services. Using the inter-VRF solution, you can use
routing policies and static routes to inject IP subnets from one VRF instance to another, and
filters to restrict access to certain protocols.
The following figure shows inter-VRF forwarding. In this solution, you can use routing policies
to leak IP subnets from one VRF to another. You can use filters to restrict access to certain
protocols. This configuration enables hub-and-spoke network designs, for example, for VoIP
gateways.
Figure 16: Inter VRF communication, internal inter-VRF forwarding
Virtual Router Redundancy Protocol
The Virtual Router Redundancy Protocol (VRRP) provides a backup router that takes over if
a router fails, which is important if you must provide redundancy mechanisms.
VRRP guidelines
VRRP provides another layer of resiliency to your network design by providing default gateway
redundancy for end users. If a VRRP-enabled router that connects to the default gateway fails,
failover to the VRRP backup router ensures no interruption for end users who attempt to route
from their local subnet.
Only the VRRP Master router forwards traffic for a given subnet. The backup VRRP router
does not route traffic destined for the default gateway.
To allow both VRRP switches to route traffic, Virtual Services Platform 4000 has an extension
to VRRP, the BackupMaster, that creates an active-active environment for routing. If you
Virtual Router Redundancy Protocol
Network Design Reference for Avaya VSP 4000 February 2014 57