CLI Guide

You can activate flow-based monitoring for a monitoring session by entering theflow-based enable
command in the Monitor Session mode. When you enable this capability, traffic with particular flows
that are traversing through the ingress and egress interfaces are examined and, appropriate ACLs can
be applied in both the ingress and egress direction. Flow-based monitoring conserves bandwidth by
monitoring only specified traffic instead all traffic on the interface. This feature is particularly useful when
looking for malicious traffic. It is available for Layer 2 and Layer 3 ingress and egress traffic. You may
specify traffic using standard or extended access-lists. This mechanism copies all incoming or outgoing
packets on one port and forwards (mirrors) them to another port. The source port is the monitored port
(MD) and the destination port is the monitoring port (MG).
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)
Access Control Lists (ACL) 309