IP Mobility: Mobile Networks Configuration Guide, Cisco IOS Release 15M&T
Cisco Mobile Networks Priority HA Assignment
Cisco Mobile Networks Priority HA Assignment
Last Updated: December 2, 2012
Before the introduction of the Cisco Mobile Networks--Priority HA Assignment feature, the mobile router preconfigured home agents (HAs) with different priorities, registering with only the highest priority home agent. However, a mobile router may roam to an area where registration with a closer home agent is more desirable. This feature allows a mobile router to register with the closer home agent using the combination of existing home agent priority configurations on the mobile router and care-of address access lists configured on the home agent.
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Information About Cisco Mobile Networks Priority HA Assignment
Feature Design of Cisco Mobile Networks Priority HA Assignment
This feature changes the behavior of the HA priority configurations on the mobile router without adding any new commands. Each HA will have an access list containing all the foreign agent care-of addresses in its region. When a mobile router sends a registration request to the best HA, the HA will accept or deny the request depending on which care-of address is used in the registration request. If the HA denies the request because the care-of address is not in the access list of that particular HA, the mobile router will try to register with the next best HA, and so on. If HAs have the same priority, then the most recently configured HA takes precedence. If registration with even the lowest priority HA fails, the mobile router will wait for an advertisement and then try to register again starting with the highest priority HA. When the mobile router registers with a new HA, it will also attempt to deregister with the old HA using the old foreign agent care-of address.
Best HA Selection Process
If more than one HA is reachable from any care-of address that may be used by the mobile router, then the HAs need an access list (which is a foreign agent care-of address or collocated care-of address) configured to enforce the best HA selection process. This configuration enforces a region covered by a specific HA defined by the care-of addresses (configured as access lists) within the region. Registrations originating outside the region are administratively denied while registrations within the region are processed.
How to Configure Cisco Mobile Networks Priority HA Assignment
Configuring Care-of Address Access Lists on an HA
This task describes how to configure care-of address access lists on an HA.
14. Repeat Steps 3 through 7 for each HA configured on the mobile router. Repeat Steps 8 through 13 for each HA if virtual networks are configured.
Care-of Address List Operation
Any time an HA has a care-of address access list configured, the access list should permit the mobile router home address (for deregistration) and the interesting list of care-of addresses (for registration).
The care-of address lists are designed to allow registrations only of a select group of care-of addresses on an HA. For priority HA assignment to work, deregistrations need to be allowed as well. The deregistration is sent with the mobile router home address in the care-of address field of the deregistration. If the home address is not permitted, any deregistration will be dropped by the access list. Priority HA assignment does not work properly if the deregistrations are dropped.
Virtual Network Advertisements
In a network using mobile routers configured with priority HA assignment and multiple HAs, the HAs may be sharing routing information. If so, each HA will advertise a route to the same mobile virtual network through the redistribute mobile command. This situaton results in multiple routes to the same virtual network, which can cause routing conflicts and lost packets. The distribute-list command configured on each HA will prevent the advertisement of the virtual-network for the mobile routers. There is no dependency on registration for this to occur.
Configuring HA Priorities on the Mobile Router
This section provides the following output example for the show ip mobile router command:
The following example shows that the mobile router is currently registered with the best home agent located at 188.8.131.52:
Router# show ip mobile router Mobile Router Enabled 01/01/02 10:01:34 Last redundancy state transition NEVER Configuration: Home Address 184.108.40.206 Mask 255.255.255.0 Home Agent 220.127.116.11 Priority 102 (best) (current) 100.100.100.1 Priority 101 Registration lifetime 90 sec Retransmit Init 1000, Max 5000 msec, Limit 3 Extend Expire 120, Retry 3, Interval 10 Monitor: Status -Registered- Active foreign agent 18.104.22.168, Care-of 22.214.171.124 On interface Ethernet5/3
Configuration Examples for Cisco Mobile Networks Priority HA Assignment
HA Priority Configuration Example
In the following example, two home agents are configured with access lists that allow the mobile router to choose the best HA to register with:
interface Loopback0 ip address 100.100.100.1 255.255.255.255 ! interface Ethernet1 ip address 126.96.36.199 255.255.255.0 ! router mobile ! router ospf 100 redistribute mobile subnets network 188.8.131.52 0.255.255.255 area 0 network 100.100.100.0 0.255.255.255 area 0 ! Suppresses virtual network to be advertised in updates distribute-list 1 out ! ip mobile home-agent care-of-access HA1-FA1 ip mobile virtual-network 184.108.40.206 255.255.255.0 ip mobile host 220.127.116.11 virtual-network 18.104.22.168 255.255.255.0 lifetime 90 ip mobile mobile-networks 22.214.171.124 description Jet network 126.96.36.199 255.255.255.0 ip mobile secure host 188.8.131.52 spi 100 key hex 12345678123456781234567812345678 algorithm md5 mode prefix-suffix ! ip access-list standard HA1-FA1 ! MR CCOA permit 184.108.40.206 ! FA1 COA permit 220.127.116.11 ! MR home address permit 18.104.22.168 ! ! Denies virtual network to access-list 1 deny 22.214.171.124 0.0.0.255 access-list 1 permit any
Home Agent 2
interface Loopback0 ip address 126.96.36.199 255.255.255.255 ! interface Ethernet0 ip address 188.8.131.52 255.255.255.0 ! router mobile ! router ospf 100 redistribute mobile subnets network 184.108.40.206 0.255.255.255 area 0 network 220.127.116.11 0.255.255.255 area 0 ! Suppresses virtual network to be advertised in update distribute-list 1 out ! ip mobile home-agent care-of-access HA2-FA2 ip mobile virtual-network 18.104.22.168 255.255.255.0 ip mobile host 22.214.171.124 virtual-network 126.96.36.199 255.255.255.0 lifetime 90 ip mobile mobile-networks 188.8.131.52 description Jet network 184.108.40.206 255.255.255.0 ip mobile secure host 220.127.116.11 spi 200 key hex 12345678123456781234567812345678 algorithm md5 mode prefix-suffix ! ip access-list standard HA2-FA2 ! FA COA permit 18.104.22.168 ! MR home address permit 22.214.171.124 ! access-list 1 deny 126.96.36.199 0.0.0.255 access-list 1 permit any
interface Loopback0 ip address 188.8.131.52 255.255.255.255 ! ! CCOA roaming interface registers with HA1 only interface Ethernet5/1 ip address 184.108.40.206 255.255.255.0 ip mobile router-service roam priority 99 ip mobile router-service collocated gateway 220.127.116.11 ! ! This roaming interface will use FA COA to register interface Ethernet5/3 ip address 18.104.22.168 255.255.255.0 ip mobile router-service roam ! ! Mobile Network interface interface Ethernet5/4 ip address 22.214.171.124 255.255.255.0 ! router mobile ! ip mobile secure home-agent 100.100.100.1 spi 100 key hex 12345678123456781234567812345678 algorithm md5 mode prefix-suffix ip mobile secure home-agent 126.96.36.199 spi 200 key hex 12345678123456781234567812345678 algorithm md5 mode prefix-suffix ! ip mobile router address 188.8.131.52 255.255.255.0 home-agent 100.100.100.1 priority 101 home-agent 184.108.40.206 priority 102 register lifetime 90
For additional information related to the Cisco Mobile Networks--Priority HA Assignment feature, see to the following sections:
care-of address --The termination point of the tunnel to a mobile node or mobile router. This can be a collocated care-of address, by which the mobile node or mobile router acquires a local address and detunnels its own packets, or a foreign agent care-of address, by which a foreign agent detunnels packets and forwards them to the mobile node or mobile router.
home agent --A router on a home network of the mobile node or that tunnels packets to the mobile node or mobile router while they are away from home. It keeps current location information for registered mobile nodes called a mobility binding .
foreign agent --A router on the visited network of a foreign network that provides routing services to the mobile node while registered. The foreign agent detunnels and delivers packets to the mobile node or mobile router that were tunneled by the home agent of the mobile node. For packets sent by a mobile node, the foreign agent may serve as a default router for registered mobile nodes.
mobile network --A network that moves with the mobile router. A mobile network is a collection of hosts and routes that are fixed with respect to each other but are mobile, as a unit, with respect to the rest of the Internet.
mobile router --A mobile node that is a router. It provides for the mobility of one or more entire networks moving together, perhaps on an airplane, a ship, a train, an automobile, or bicycle. The nodes connected to a network served by the mobile router may themselves be fixed nodes or mobile nodes or routers.
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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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