Users Guide
Related Commands
• ip access-list extended — create an extended ACL.
•
• permit tcp — assign a permit lter for TCP packets.
• permit udp — assign a permit lter for UDP packets.
permit tcp
To pass TCP packets meeting the lter criteria, congure a lter.
Syntax
permit tcp {source mask | any | host ip-address} [bit] [operator port [port]]
{destination mask | any | host ip-address} [bit] [dscp] [operator port [port]]
[count [byte] [order] [fragments] [no-drop]
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 /prex format (/x) or A.B.C.D. The mask, when specied 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
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
202 Access Control Lists (ACL)