Administrator Guide

You can activate flow-based monitoring for a monitoring session by entering the flow-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).
deny tcp (for IPv6 ACLs)
Configure a filter that drops TCP packets that match the filter criteria.
Syntax
deny 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 syntax if you know the filter’s sequence number
• Use the no deny 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
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) 309