Users Guide

To remove this lter, you have two choices:
• Use the no seq sequence-number command if you know the lter’s sequence number.
• Use the no permit tcp {source mask | any | host ip-address} {destination mask |
any | host
ip-address} command.
Parameters
source Enter the IP address of the network or host from which the packets were sent.
mask Enter a network mask in /prex format (/x) or A.B.C.D. The mask, when specied in
A.B.C.D format, may be either contiguous or non-contiguous.
any Enter the keyword any to specify that all routes are subject to the lter.
host ip-address Enter the keyword host then the IP address to specify a host IP address.
bit Enter a ag or combination of bits:
• ack: acknowledgement eld
• fin: nish (no more data from the user)
• psh: push function
• rst: reset the connection
• syn: synchronize sequence numbers
• urg: urgent eld
• established: datagram of established TCP session
Use the established ag to match only ACK and RST ags of established TCP
session.
You cannot use established along with the other control ags
While using the established ag in an ACL rule, all the other TCP control ags are
masked, to avoid redundant TCP control ags conguration in a single rule. When you use
any TCP control ag in an ACL rule, established is masked and other control ags are
available.
dscp Enter the keyword dscp to deny a packet based on the DSCP value. The range is from 0
to 63.
operator (OPTIONAL) Enter one of the following logical operand:
• eq = equal to
• neq = not equal to
• gt = greater than
• lt = less than
• range = inclusive range of ports (you must specify two ports for the port parameter)
port port Enter the application layer port number. Enter two port numbers if you are using the
range logical operand. The range is from 0 to 65535.
The following list includes some common TCP port numbers:
• 23 = Telnet
• 20 and 21 = FTP
• 25 = SMTP
214 Access Control Lists (ACL)