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Configuring Mobile IP
Prerequisites
IPC-166
Cisco IOS IP Configuration Guide
For MNs on virtual networks, the active and standby HAs are peers—either HA can handle registration
requests from the MN and update the mobility binding table on the peer HA.
When a standby HA comes up, it must request all mobility binding information from the active HA. The
active HA responds by downloading the mobility binding table to the standby HA. The standby HA
acknowledges that it has received the requested binding information. See (b) in Figure 29 for an example
of an active HA downloading the mobility bindings to a standby HA. A main concern in this stage of the
process is which HA IP interface the standby HA should use to retrieve the appropriate mobility binding
table and on which interface of the standby HA the binding request should be sent.
Figure 29 Mobility Binding Process
Managing Mobility Binding Tables
When a binding is cleared on an active home agent, it will not be cleared on the standby/peer home agent.
If you want to clear the binding on the standby/peer home agent, you must manually clear it using the
clear ip mobile binding command. This design ensures that binding information will not be accidentally
lost.
It is possible that binding tables of two home agents in a redundancy group might be out of
synchronization because of a network problem. You can force the synchronization of the binding tables
by using the clear ip mobile binding all load standby-group-name command.
Prerequisites
To configure home agent functionality on your router, you need to determine IP addresses or subnets for
which you want to allow roaming service. If you intend to support roaming on virtual networks, you need
to identify the subnets for which you will allow this service and place these virtual networks
appropriately on the home agent. It is possible to enable home agent functionality for a physical or
virtual subnet. In the case of virtual subnets, you must define the virtual networks on the router using
the ip mobile virtual-network global configuration command. Mobile IP home agent and foreign agent
services can be configured on the same router or on separate routers to enable Mobile IP service to users.
Active
home
agent
Standby
home
agent
Binding
info
reply
Binding
info request
Binding info
reply acknowledgment
(b) Downloading mobility
Binding tables
(a) Updating binding information
after registration
Active
home
agent
Standby
home
agent
Binding
update
Binding update
acknowledgment
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