Mobile IP Technology and Applications

Summary 115

When to Use Peer-Peer Home Agent Redundancy

On the surface, peer-peer configuration looks like an ideal way to improve network capacity and

performance. When you look closer, however, you can see that this might not be the case. First,

it does not afford extra capacity; the memory used by each Home Agent is the same because the

binding table is replicated. Second, minimal gains are found in signaling capacity because the

processing necessary to add a binding on the active Home Agent is only slightly more than that

for adding a binding on a standby Home Agent.

Peer-peer redundancy adds value in two deployment scenarios. In networks where AAA server

latency is high, peer-peer redundancy can provide added capacity because processing a binding

on just the active Home Agent takes far longer than sharing the responsibility. The second case

is in networks where Home Agents must use more than one interface for redundancy. This can

mitigate some failure scenarios in networks where both Home Agents could be up and

accepting bindings when a single link is down.

Summary

The campus mobility model is the simplest of Mobile IP deployments, and it provides us with

a chance to look at some of the key features of IOS Mobile IP.

In this chapter, integration with AAA was discussed, and RADIUS was identified as the optimal

protocol for AAA services. The details surrounding the Cisco ZeCC should have made it clear

that this is an ideal solution for enterprise deployment because of the simplified client rollout

and the integration with existing backend systems.

Home Agent Redundancy was introduced as a critical component to a high-availability Mobile

IP solution. The use of Home Agent Redundancy in its simplest form—the active-standby

mode—is the ideal deployment in most cases. The added complexity of peer-peer redundancy

is only necessary in a few deployment scenarios. Remember, when discussing active-standby

ip mobile virtual-network 20.0.0.0 255.0.0.0

ip mobile virtual-network 30.0.0.0 255.0.0.0

ip mobile virtual-network 40.0.0.0 255.0.0.0 address 40.0.0.1

! Used to map to the HSRP groups SanJoseHANet1 and SanJoseHANet2

ip mobile home-agent redundancy SanJoseHANet1 virtual-network

ip mobile home-agent redundancy SanJoseHANet2 virtual-network

! Configure security association with Peer Home Agent

ip mobile secure home-agent 1.0.0.1 spi 100 key hex

00112233445566778899001122334455

ip mobile secure home-agent 2.0.0.1 spi 100 key hex

00112233445566778899001122334455

Example 5-6 Home Agent Redundancy in Peer-Peer Formation Using Multiple Physical Networks (Continued)