Emetric

The emetric (Extended Metric) consists of both the standard routing metric and the SRI. The emetric is stored in each route's entry in the routing table. The routing software selects the shortest path that satisfies the security requirements by comparing emetrics. Alternately, the emetric can be entered manually for static routes using the route(1M). (See "Routing Table" for how routes are manually defined.)

If dynamic routing is used, the routing daemon, in.routed broadcasts a special type of security-enhanced response packet advertising the known routes.

Several routes through multiple gateways may exist between a sending and receiving host, and the emetric for each route may be different.