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.
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 188.8.131.52 255.0.0.0
ip mobile virtual-network 184.108.40.206 255.0.0.0
ip mobile virtual-network 220.127.116.11 255.0.0.0 address 18.104.22.168
! 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 22.214.171.124 spi 100 key hex
ip mobile secure home-agent 126.96.36.199 spi 100 key hex
Example 5-6 Home Agent Redundancy in Peer-Peer Formation Using Multiple Physical Networks (Continued)