VRRP: Increasing Reliability and Failover with the Virtual Router Redundance Protocol

6.1. VRRP and Firewalls

Firewalls, simply stated, are packet filters with varying degrees of sophistication. Their purpose is to filter out both the packets that are not supposed to come inside a protected network and the packets that are not supposed to go outside. One aspect of a firewall's filtering is of relevance to the VRRP discussion. Firewalls can apply some stateless filters to enforce their specified policies, but often the filters may be based on certain states under inspection—for example, a session context. Since VRRP's sole purpose is the protection of first hop default routers, it does not contain any element that can synchronize and preserve the potential states of a firewall. These states need to be handled by specialized protocols ...