Where <icmp> is { type <number> [code <number>] | name <name> | group <group> }.

You can specify an ICMP type code in one of several different ways:

• By type, such as 128 (echo-request)
• By a type and code pair, such as type 1 and code 4 (port unreachable)
• By an explicit name <name> argument, such as name echo-request

type <number>

Specifies the numeric identifier of an ICMP type.

code <number>

Specifies the numeric identifier of an ICMP code.

name <name>

Specifies the name of an ICMP type.

group <group>

Specifies an IPv4 ICMP group.