FreeBSD 8.2-ipfw-icmp

Question

FreeBSD

Hi2all.
How to conduct icmp (specifically ping) through a specific interface?
Thank you.

Answer 1

and also for FreeBSD
ping - classic ICMP
trace - UDP + ICMP (unix style)
S - Sender Device
I - Intermediate Device (Router)
D - Destination IP
PING
S->D Send ICMP-8 packets to network hosts
S<-D Receive from destination ICMP-0
TRACEROUTE
S: -> Sends UDP datagram to dest port>=33434, src port random, TTL=1 (next packet — UDP destination port is incremented)
I: <-> Receive from any router ICMP-11 with TTL=1
D: < - Destination reached - Receive ICMP-3, code 3 ("destination unreachable," "port unreachable") (ICMP "udp port 33435 unreachable")
OR A "host unreachable," "net unreachable," "maximum TTL exceeded," or a "timeout" type of message, which means that the probe is resent.