Cisco ASA 5505 - Manual (Page 452)

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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 22 Configuring Static and Default Routes
Monitoring a Static or Default Route
Note The ipv6 route command works the same way as the route command, which is used to define IPv4 static
routes.
Monitoring a Static or Default Route
One of the problems with static routes is that there is no inherent mechanism for determining if the route
is up or down. They remain in the routing table even if the next hop gateway becomes unavailable. Static
routes are only removed from the routing table if the associated interface on the ASA goes down.
The static route tracking feature provides a method for tracking the availability of a static route and
installing a backup route if the primary route should fail. For example, you can define a default route to
an ISP gateway and a backup default route to a secondary ISP in case the primary ISP becomes
unavailable.
The ASA implements this feature by associating a static route with a monitoring target that you define,
and monitors the target using ICMP echo requests. If an echo reply is not received within a specified
time period, the object is considered down and the associated route is removed from the routing table. A
previously configured backup route is used in place of the removed route.
When selecting a monitoring target, you need to make sure that it can respond to ICMP echo requests.
The target can be any network object that you choose, but you should consider using the following:
• The ISP gateway (for dual ISP support) address
• The next hop gateway address (if you are concerned about the availability of the gateway)
• A server on the target network, such as a AAA server, that the ASA needs to communicate with
• A persistent network object on the destination network
Note A desktop or notebook computer that may be shut down at night is not a good choice.
You can configure static route tracking for statically defined routes or default routes obtained through
DHCP or PPPoE. You can only enable PPPoE clients on multiple interfaces with route tracking
configured.
To configure static route tracking, perform the following steps: