Reference Guide
You can activate ow-based mirroring of trac by using the flow-based enable command. Trac with particular ows that are
traversing through the ingress interfaces are examined. Appropriate ACL rules apply in the ingress direction. By default, ow-based
mirroring is not enabled.
To enable the evaluation and replication of trac traversing to the destination port, congure the monitor option with the permit, deny,
or seq commands for ACLs assigned to the source or the monitored port (MD). Enter the keywords capture session session-id
with the seq, permit, or deny command for the ACL rules to allow or drop IPv4, IPv6, ARP, UDP, EtherType, ICMP, and TCP packets.
IPV4-ACL mode
seq sequence-number {deny | permit} {source [mask] | any | host ip-address} [count [byte]]
[fragments] [threshold-in-msgs count] [capture session session-id]
If you congure the flow-based enable command and do not apply an ACL on the source port or the monitored port, both ow-based
monitoring and port mirroring do not function. Flow-based monitoring is supported only for ingress trac and not for egress packets.
The show monitor session session-id command displays output which indicates if a particular session is enabled for ow-
monitoring.
View ow-based monitoring
OS10# show monitor session 1
S.Id Source Destination Dir SrcIP DstIP DSCP TTL State Reason
----------------------------------------------------------------------------
1 ethernet1/1/1 ethernet1/1/4 both N/A N/A N/A N/A true Is UP
Trac matching ACL rule
OS10# show ip access-lists in
Ingress IP access-list testflow
Active on interfaces :
ethernet1/1/1
seq 5 permit icmp any any capture session 1 count (0 packets)
seq 10 permit ip 102.1.1.0/24 any capture session 1 count bytes (0 bytes)
seq 15 deny udp any any capture session 2 count bytes (0 bytes)
seq 20 deny tcp any any capture session 3 count bytes (0 bytes)
Enable ow-based monitoring
Flow-based monitoring conserves bandwidth by mirroring only specied trac, rather than all trac on an interface. It is available for L2
and L3 ingress and egress trac. You can congure trac to be monitored using ACL lters.
1 Create a monitor session in MONITOR-SESSION mode.
monitor session session-number type local | rspan-source
2 Enable ow-based monitoring for the mirroring session in MONITOR-SESSION mode.
flow-based enable
3 Dene ACL rules that include the keywords capture session session-id in CONFIGURATION mode. The system only
considers port monitoring trac that matches rules with the keywords capture session.
ip access-list
4 Apply the ACL to the monitored port in INTERFACE mode.
ip access-group access-list
5 Save the conguration.
do commit
Enable ow-based monitoring
OS10(config)# monitor session 1 type local
OS10(conf-mon-local-1)# flow-based enable
OS10(config)# ip access-list testflow
OS10(conf-ipv4-acl)# seq 5 permit icmp any any capture session 1 count
386
Access Control Lists