Reference Guide

You can activate ow-based mirroring of trac by using the flow-based enable command. Trac 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 trac traversing to the destination port, congure 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 congure 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 trac 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
Trac 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 specied trac, rather than all trac on an interface. It is available for L2
and L3 ingress and egress trac. You can congure trac 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 Dene ACL rules that include the keywords capture session session-id in CONFIGURATION mode. The system only
considers port monitoring trac 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 conguration.
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