Setup 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).
Related
Commands
● permit – assign a permit filter for IP packets.
permit icmp (for IPv6 ACLs)
To allow all or specific internet control message protocol (ICMP) messages, configure a filter.
Syntax
permit icmp {source address mask | any | host ipv6-address} {destination
address | any | host ipv6-address} [message-type] [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 icmp {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) 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-
v6address
Enter the keyword host then the IPv6 address to specify a host IP address.
destination Enter the IP address of the network or host to which the packets are sent.
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:
● 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.
count (OPTIONAL) Enter the keyword count to count packets processed by the filter.
byte (OPTIONAL) Enter the keyword byte to count bytes processed by the filter.
log (OPTIONAL) Enter the keyword log to enable the triggering of ACL log messages.
threshold-in
msgs count
(OPTIONAL) Enter the threshold-in-msgs keyword followed by a value to
indicate the maximum number of ACL logs that can be generated, exceeding
which the generation of ACL logs is terminated with the seq, permit, or deny
commands. The threshold range is from 1 to 100.
interval minutes (OPTIONAL) Enter the keyword interval followed by the time period in minutes
at which ACL logs must be generated. The interval range is from 1 to 10 minutes.
Access Control Lists (ACL) 279