7-14 Reference Guide3. Using the tables on page 7-10, find the destination port andprotocol numbers (thelocal Telnet port):n Proto = TCP (or 6)n D. Port = 234. The filter should be enabled and instructed to block the Telnetpackets containing the source address shown in step 2:n On? = Yesn Fwd = NoThis four-step process is how we produced the following filter fromthe original rule:+-#--Source IP Addr--Dest IP Addr-----Proto-Src.Port-D.Port--On?-Fwd+--------------------------------------------------------------------+1 199.211.211.17 0.0.0.0 TCP 23 Yes NoFiltering example #2Suppose a filter is configured to block all incoming IP packets withthe source IP address of 200.233.14.0, regardless of the type ofconnection or its destination. The filter would look like this:+-#--Source IP Addr--Dest IP Addr-----Proto-Src.Port-D.Port--On?-Fwd+--------------------------------------------------------------------+1 200.233.14.0 0.0.0.0 0 Yes NoThis filter blocks any packets coming from a remote network withthe IP network address 200.233.14.0. The 0 at the end of theaddress signifiesany host on the class C IP network 200.233.14.0.If, for example, the filter is applied to a packet with the source IPaddress 200.233.14.5, it will block it.In this case, the mask, which does not appear in the table, must beset to 255.255.255.0. This way, all packets with a source addressof 200.233.14.x will be matched correctly, no matter what the finaladdress byte is.Note: The protocol attribute for this filter is 0 by default. This tellsthe filter to ignore the IP protocol or type of IP packet.
