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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
s 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 the specified traffic instead of 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
ip access-list standard— configures a standard ACL.
permit — configures a MAC address filter to pass packets.
seq — configures a MAC address filter with a specified sequence number.
permit (for Standard IP ACLs)
To permit packets from a specific source IP address to leave the switch, configure a filter.
Syntax
permit {source [mask]| any | host ip-address} [no-drop] [count [byte]]
[dscp value] [order] [fragments] [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 {source [mask] | any | host ip-address} command.
Parameters
source Enter the IP address in dotted decimal format of the network from which the
packet was sent.
mask (OPTIONAL) 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-address Enter the keyword host then the IP address to specify a host IP address or
hostname.
no-drop Enter the keywords no-drop to match only the forwarded packets.
count (OPTIONAL) Enter the keyword count to count packets processed by the filter.
bytes (OPTIONAL) Enter the keyword bytes to count bytes processed by the filter.
dscp (OPTIONAL) Enter the keyword dcsp to match to the IP DCSCP values.
order (OPTIONAL) Enter the keyword order to specify the QoS priority for the ACL
entry. The range is from 0 to 254 (where 0 is the highest priority and 254 is the
lowest; lower-order numbers have a higher priority). If you do not use the keyword
order, the ACLs have the lowest order by default (255).
fragments Enter the keyword fragments to use ACLs to control packet fragments.
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
206 Access Control Lists (ACL)