IRDP Support Overview

ICMP Router Discovery Protocol (IRDP) is an ICMP message exchange between a host and a router. The security device is the router and advertises the IP address of a specified interface periodically or on demand. If the host is configured to listen, you can configure the security device to send periodic advertisements. If the host explicitly sends router solicitations, you can configure the security device to respond on demand.

Before a host can send IP datagrams beyond its directly connected subnet, it must discover the address of at least one operational router on that subnet.IRDP is a router discovery method that uses a pair of ICMP messages for use on multicast links. The messages are called router advertisements (RA) and router solicitations (RS). Each router periodically multicasts an RA from each of its multicast interfaces, announcing the IP address(es) of that interface. Hosts discover routers simply by listening for adverstisements. The host may send out router solicitation messages seeking immediate advertisements at startup, rather than wait for periodic updates.

Note: ICMP Router Discovery Protocol (IRDP) is supported on all devices running ScreenOS 6.3, including the SSG520.

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