Deployment Guide

deny tcp
Configure a filter that drops transmission control protocol (TCP) packets meeting the filter criteria.
Syntax
deny tcp {source mask | any | host ip-address} [bit] [operator port [port]]
{destination mask | any | host ip-address} [ttl operator] [dscp] [bit]
[operator port [port]] [count [bytes] [order] [fragments] [monitor] [no-
drop]
To remove this filter, you have two choices:
● Use the no seq sequence-number command if you know the filter’s sequence number.
● Use the no deny 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 are sent.
mask Enter a network mask in /prefix format (/x) or A.B.C.D. The mask, when specified
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 filter.
host ip-address Enter the keyword host then the IP address to specify a host IP address.
ttl Enter the keyword ttl to deny a packet based on the time to live value. The range
is from 1 to 255.
operator Enter one of the following logical operand:
● eq(equal to) — matches packets that contain a ttl value that is equal to the
specified ttl value.
● neq(not equal to) — matches packets that contain a ttl value that is not equal
to the specified ttl value.
● gt(greater than) — matches packets that contain a ttl value that is greater
than the specified ttl value.
● lt (less than) — matches packets that contain a ttl value that is less than the
specified ttl value.
● range(inclusive range of values) — matches packets that contain a ttl value
that falls between the specified range of ttl values.
dscp Enter this keyword dscp to deny a packet based on the DSCP value. The range is
from 0 to 63.
bit Enter a flag or combination of bits:
● ack: acknowledgement field
● fin: finish (no more data from the user)
● psh: push function
● rst: reset the connection
● syn: synchronize sequence numbers
● urg: urgent field
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
command)
port port
Enter the application layer port number. Enter two port numbers if 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
200 Access Control Lists (ACL)