Source port filtering is most interesting when the source system is a
system under your control. I use source port filtering to control packets
outbound from the network under my control. I use it for controlling TCP
traffic in *both* directions. Being a "belt and suspenders" person I
prefer to control the flow of traffic both inbound and outbound. For that
I want source port filtering for packets outbound from my network.
No, I do not trust the source port value in a packet coming in from the
larger Internet and I therefore agree with the gentleman from cisco that
source port is of considerably less interest for use with packets coming
from hosts not within my control.
Brian Lloyd, President Lloyd Internetworking
com 3031 Alhambra Drive
(916) 676-1147 - voice Suite 102
(916) 676-3442 - fax Cameron Park, CA 95682