Customizes the packet filter string.
Syntax:
Protocol+Direction+Host(s)+ Value
+Logical Operations+Other Expression
Protocol:
Values: ether, fddi, ip, arp, rarp, decnet,
lat, sca, moprc, mopdl, tcp and udp.
Application-level protocol, such as
http, dns and sip are not supported.
If no protocol is specified, all the
protocols are used.
Direction:
Values: src, dst, src and dst, src or dst
If no source or destination is specified,
the "src or dst" keywords are applied.
For example: "host 10.2.2.2" is
equivalent to "src or dst host 10.2.2.2".
Host(s):
Values: net, port, host, portrange.
If no host(s) is specified, the "host"
keyword is used.
For example: "src 10.1.1.1" is equivalent
to "src host 10.1.1.1".
Logical Operations:
Values: not, and, or.
Negation ("not") has highest
precedence. Alternation ("or") and
concatenation ("and") have equal
precedence and associate left to right.
For example:
"not tcp port 3128 and tcp port 23" is
equivalent to "(not tcp port 3128) and
tcp port 23".
"not tcp port 3128 and tcp port 23" is
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