On Tue, 17 Apr 2001, mjn wrote: >$IPCHAINS -A input -p tcp -s 24.0.0.0/24 -d $LOCALNET 25 -j ACCEPT > >I also tried it without the port number. My big problem is not >understanding what the mask "/24" is doing in this case (and many >others)... Well, given an IP address (or network number in this case): 24.0.0.0, and a mask: /24 (ie 255.255.255.0, 24 bits on, remember IP addressing is 32 bits, with each quad being 8 bits), you get to know the network/subnet part and the host part. In this case the first three quads "24.0.0" is the network/subnet part, leaving one quad for the host part. The above rule allows packets with source addresses falling in the range 24.0.0.1-24.0.0.254. check out http://www.tcpipprimer.com/addressing.cfm hope that helps - Ryan