CLI Guide

and the packet count for that new interval commences from zero. If ACL logging was stopped previously
because the configured threshold is exceeded, it is re-enabled for this new interval.
If ACL logging is stopped because the configured threshold is exceeded, it is re-enabled after the logging
interval period elapses. ACL logging is supported for standard and extended IPv4 ACLs, IPv6 ACLs, and
MAC ACLs. You can configure ACL logging only on ACLs that are applied to ingress interfaces; you
cannot enable logging for ACLs that are associated with egress interfaces.
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
294 Access Control Lists (ACL)