White Papers

permit tcp (for IPv6 ACLs)
Configure a filter to pass TCP packets that match the filter criteria.
Syntax
permit tcp {source address mask | any | host ipv6-address} [operator port
[port]] {destination address | any | host ipv6-address} [bit] [operator
port [port]] [ttl operator] [count [byte]] [log [interval minutes]
[threshold-in-msgs [count]] [monitor]
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 permit tcp {source address mask | any | host ipv6-address}
{destination address | any | host ipv6-address} command.
Parameters
source address
mask
Enter a network mask in /prefix format (/x).
any Enter the keyword any to specify that all routes are subject to the filter.
host ipv6-
address
Enter the keyword host then the IP address to specify a host IP address.
destination
address
Enter the IPv6 address of the network or host to which the packets are sent.
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
● established: datagram of established TCP session
Use the established flag to match only ACK and RST flags of established TCP
session.
You cannot use established along with the other control flags
While using the established flag in an ACL rule, all the other TCP control flags
are masked, to avoid redundant TCP control flags configuration in a single rule.
When you use any TCP control flag in an ACL rule, established is masked and
other control flags are available.
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
● 169 = SNMP
ttl Enter the keyword ttl to permit a packet based on the time to live value. The
range is from 1 to 255.
operator Enter one of the following logical operand:
Access Control Lists (ACL) 297