Mobile IP - Foreign Agent Local Routing to Mobile Networks

The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature allows traffic from a correspondent node on a local subnet to route directly through the foreign agent (FA) to a mobile network that is visiting the FA. This direct routing is accomplished by injecting mobile network routes into the routing table of the FA.

This feature is useful in scenarios in which a mobile router needs to receive high bandwidth traffic, such as streaming video, from a device on the local LAN of the FA. An example of such a scenario is diagrammed in the figure below.

Figure 1

Usage Scenario for the Mobile IP - Foreign Agent Local Routing to Mobile Networks Feature

In this scenario, a police officer has been called to a bank where an incident is occurring. The mobile router in the police officer's car registers with the FA and connects to the video streaming server, a correspondent node, that is located inside the bank. The police officer may then watch live video of the incident that is occurring inside the bank, gaining valuable information about how to proceed with handling the incident safely.

Before the introduction of the Mobile IP - Foreign Agent Local Routing to Mobile Networks feature, the streaming video from the correspondent node in the bank would be routed from the FA to the HA, then back to the FA, and finally to the mobile router. This behavior, known as triangular routing, is not desirable for latency-sensitive applications. If a second police car arrived and wanted to watch the video as well, the already limited bandwidth between the FA and the HA would be even further taxed. The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature allows traffic from the local corresponding node to be routed directly from the FA to the mobile router, eliminating the unnecessary trip to the HA.

The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature improves latency by allowing the FA to route traffic directly to mobile networks rather than routing through the HA. This feature is useful in scenarios in which a mobile router needs to receive high bandwidth traffic, such as streaming video, from a device on the local LAN of the FA. This feature can also be useful any time that the bandwidth between the FA and the HA is limited.

1.    enable

2.    configure terminal

3.    ip mobile foreign-agent inject-mobile-networks [mobnetacl access-list-identifier]

4.    ip mobile secure {aaa-download | host | visitor | home-agent| foreign-agent| proxy-host} {lower-address[upper-address] | nai string} {inbound-spi spi-in outbound-spi spi-out | spi spi} key hex string [replay timestamp [number]] [algorithm {md5 mode prefix-suffix| hmac-md5}]

• Troubleshooting Tips

To restrict which mobile networks will have their local routes injected into the FA routing table, you may choose to configure an access list. You can configure either a named access list or a numbered access list. Perform one of the following tasks to configure an access list on the FA:

• Configuring a Named Access List
• Configuring a Numbered Access List

The following example configures the FA for local routing and uses a named access list:

ip mobile foreign-agent care-of Ethernet2/2
ip mobile foreign-agent inject-mobile-networks mobnetacl mobile-net-list
ip mobile foreign-agent reg-wait 120
ip mobile secure home-agent 10.10.10.1 spi 1400 key hex 12345678123456781234567812345678      algorithm hmac-md5
!
ip access-list standard mobile-net-list
 permit any

The following example configures the FA for local routing and uses a numbered access list:

ip mobile foreign-agent care-of Ethernet2/2
ip mobile foreign-agent inject-mobile-networks mobnetacl 88
ip mobile foreign-agent reg-wait 120
ip mobile secure home-agent 10.10.10.1 spi 1400 key hex 12345678123456781234567812345678      algorithm hmac-md5
!
access-list 88 permit any