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).
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} [type] [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.
type Enter the ICMP packet type. The following types are available:
For IPv4:
echo count
echo-reply count
host-unreachable count
host-unknown count
network-unknown count
net-unreachable count
packet-too-big count
parameter-problem count
port-unreachable count
source-quench count
time-exceeded count
For IPv6:
echo count
echo-reply count
nd-ns count
nd-na count
packet-too-big count
parameter-problem count
time-exceeded count
port-unreachable count
The ICMP packets cannot be filtered using mirroring ACL.
Access Control Lists (ACL)
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