Dynamic crypto map entries, like regular static crypto map entries, are grouped into sets. A set is a group of dynamic crypto map entries all with the same dynamic map name, but each with a different dynamic sequence number. Each member of the set may be configured for RRI.

To create a dynamic crypto map entry and enable RRI, perform the steps in this section.

Before configuring RRI on a static crypto map, note that:

• Routes are not created based on access list 102, as reverse-route is not enabled on mymap 2. RRI is not enabled by default and is not displayed in the router configuration.
• Enable a routing protocol to distribute the VPN routes to upstream devices.
• If Cisco Express Forwarding (CEF) is run on a VPN router configured for RRI, adjacencies need to be formed for each RRI injected network through the next hop device. As the next hop is not explicitly defined in the routing table for these routes, proxy-ARP should be enabled on the next hop router, which allows the CEF adjacency to be formed using the Layer 2 addresses of that device. In cases where there are many RRI injected routes, adjacency tables may become quite large, as an entry is created for each device from each of the subnets represented by the RRI route.

To add RRI to a static crypto map set, perform the steps in this section.

When configuring HSRP with IPsec, the following conditions may apply:

• When HSRP is applied to a crypto map on an interface, the crypto map must be reapplied if the standby IP address or the standby name is changed on that interface.
• If HSRP is applied to a crypto map on an interface, and you delete the standby IP address or the standby name from that interface, the crypto tunnel endpoint is reinitialized to the actual IP address of that interface.
• If you add the standby IP address and the standby name to an interface with the requirement IPsec failover, the crypto map must be reapplied with the appropriate redundancy information.
• Standby priorities should be equal on active and standby routers. If they are not, the higher priority router takes over as the active router. If the old active router comes back up and immediately assumes the active role before having time to report itself, standby and sync connections will be dropped.
• The IP addresses on the HSRP-tracked interfaces on the standby and active routers should both be either lower or higher on one router than the other. In the case of equal priorities (an HA requirement), HSRP will assign the active state-based IP address. If an addressing scheme exists so that the public IP address of router A is lower than the public IP address of router B, but the opposite is true for their private interfaces, an active/standby-standby/active split condition could exist, which will break connectivity.

Note	To configure HSRP without IPsec, refer to the "Configuring IP Services" module in the IP Application Services Configuration Guide.

To apply a crypto map set to an interface, perform the steps in this section.

In the following example, using the reverse-route command in the definition of the dynamic crypto map template ensures that routes are created for any remote proxies (subnets or hosts), protected by the connecting remote IPsec peers.

crypto dynamic mydynmap 1
 set transform-set my-transform-set
 reverse-route

This template is then associated with a "parent" crypto map statement and then applied to an interface.

crypto map mymap 3 ipsec-isakmp dynamic mydynmap
 interface FastEthernet 0/0
 crypto map mymap

RRI is a good solution for topologies that require encrypted traffic to be diverted to a VPN router and all other traffic to a different router. In these scenarios, RRI eliminates the need to manually define static routes on devices.

RRI is not required if a single VPN router is used, and all traffic passes through the VPN router during its path in to and out of the network.

If you choose to manually define static routes on the VPN router for remote proxies and have these routes permanently installed in the routing table, RRI should not be enabled on the crypto map instance that covers the same remote proxies. In this case, there is no possibility of user-defined static routes being removed by RRI.

Routing convergence can affect the success of a failover based on the routing protocol used to advertise routes (link state versus periodic update). We recommend that a link state routing protocol such as OSPF be used to help speed convergence time by ensuring that routing updates are sent as soon as a change in routing state is detected.

In the following example, RRI is enabled for mymap 1, but not for mymap 2. Upon the application of the crypto map to the interface, a route is created based on access-list 101 analogous to the following:

IP route 172.17.11.0 255.255.255.0 FastEthernet 0/0
crypto map mymap 1 ipsec-isakmp
 set peer 172.17.11.1
 reverse-route
 set transform-set my-transform-set
 match address 101
crypto map mymap 2 ipsec-isakmp
 set peer 10.1.1.1
 set transform-set my-transform-set
 match address 102
access-list 101 permit ip 192.168.1.0 0.0.0.255 172.17.11.0 0.0.0.255 
access-list 102 permit ip 192.168.1.0 0.0.0.255 10.0.0.0 0.0.255.255
interface FastEthernet 0/0
 crypto map mymap

The following example shows how all remote VPN gateways connect to the router via 192.168.0.3. The crypto map on the interface binds this standby address as the local tunnel endpoint for all instances of the crypto map named mymap and at the same time ensures that HSRP failover is facilitated between an active and standby device belonging to the same standby group named group1.

Note that RRI also provides the ability for only the active device in the HSRP group to be advertising itself to inside devices as the next hop VPN gateway to the remote proxies. If there is a failover, routes are deleted on the formerly active device and created on the newly active device.

crypto map mymap 1 ipsec-isakmp
 set peer 10.1.1.1
 reverse-route
 set transform-set esp-aes-sha
 match address 102
Interface FastEthernet 0/0
 ip address 192.168.0.2 255.255.255.0
 standby name group1
 standby ip 192.168.0.3
 crypto map mymap redundancy group1
access-list 102 permit ip 192.168.1.0 0.0.0.255 10.0.0.0 0.0.255.255

The standby name needs to be configured on all devices in the standby group, and the standby address needs to configured on at least one member of the group. If the standby name is removed from the router, the IPsec SAs will be deleted. If the standby name is added again, regardless of whether the same name or a different name is used, the crypto map (using the redundancy option) will have to be reapplied to the interface.