High Availability

There are no direct provisions within the IPsec standards regarding HA. As such, vendors have impleme proprietary solutions to this problem. There are four potential methods of implementing IPsec HA:

• Hot standby Failover sessions using a protocol like Virtual Router Redundancy Protocol (VRRP) or Routing Protocol (HSRP).

• Stateful hot standby Failover sessions using one of the preceding protocols and transferring the information from one device to another.

• Round robin Most common in remote user configurations giving a list of gateways to the client, w succession in the event the first fails.

• Routing convergence Configure IPsec links to multiple head-end devices using GRE tunnels and the event of a failure, the other IPsec tunnel will be used as fast as the routing protocol can convei is used, each IPsec gateway need not be located in the same facility; routing can be used to deteri gateway to route the traffic.

The first three options can be combined with some sort of load-balancing mechanism to make the best i hardware. The routing convergence option can also be deployed in a load-balancing manner by dividing secondary tunnels to different head-end devices, as shown in Figure 10-28.

Figure 10-28. Load-Balanced Site-to-Site Routed IPsec Desigi

Figure 10-28. Load-Balanced Site-to-Site Routed IPsec Desigi

Here you can see that each of the three devices has exactly one third of the primary tunnels and one th tunnels. This way, in the event of a head-end failure, the other two running gateways each can pick up gateway's load. Managing this configuration can be difficult because tracking which remote branch shou which central-site device gets very difficult as the number of central-site devices increases.

The first three HA options are primarily useful for remote user connections because they don't use routi is large enough that you need HA, you probably need routing, which will steer you toward the routing cc for your site-to-site networks.

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