The ICMP Router Solicitation message is a part of ICMP Internet Router Discovery Protocol (IRDP). ICMP Internet Router Discovery Protocol (IRDP) is defined in RFC 1256. ICMP Router Solicitation message allows a computer inside a network to find its default gateway by sending a solicited message to IPv4 multicast address 126.96.36.199 (All routers multicast address) seeking default gateway information.
ICMP Router Solicitation message Type number is 10. Please click next link, if you are not sure what are Type and Code fields in ICMP header.
All Routers in the network segment listening to multicast link-local IPv4 address 188.8.131.52, will reply with an ICMP Router Advertisement message to announce default gateway IPv4 address. Even though routers advertise their presence in the network by using ICMP Router Advertisement messages periodically, ICMP Router Solicitation message allows a computer to receive default gateway information immediately without having to wait for periodical ICMP Router Advertisement messages.