Port Mirroring - Alcatel-Lucent 7750 SR OS Service Manual

VPLS Features

Port Mirroring

A SAP created on an access port that is currently defined as an egress mirror source may not be
defined into an egress multicast group.
A port that has a SAP defined in an egress multicast group may not be defined as an egress mirror
source. If egress port mirroring is desired, then all SAPs on the port must first be removed from all
egress multicast groups.
Filter Mirroring
An IP or MAC filter that is currently defined on an egress multicast group as a common required
parameter may not have an entry from the list defined as a mirror source.
An IP or MAC filter that has an entry defined as a mirror source may not be defined as a common
required parameter for an egress multicast group.
If IP or MAC based filter mirroring is required for packets that egress an egress multicast group
SAP, the SAP must first be removed from the egress multicast group and then an IP or MAC filter
that is not associated with an egress multicast group must be assigned to the SAP.
SAP Mirroring
While SAP mirroring is not allowed within an IOM chain of SAPs, it is possible to define an
egress multicast group member SAP as an egress mirror source. When the IOM encounters a
chained SAP as an egress mirror source, it automatically removes the SAP from its chain, allowing
packets that egress the SAP to hit the mirror decision. Once the SAP is removed as an egress
mirror source, the SAP will be automatically placed back into a chain by the IOM.
It should be noted that all mirroring decisions affect forwarding plane performance due to the
overhead of replicating the frame to the mirror destination. This is especially true for efficient
multicast replication as removing the SAP from the chain also eliminates a portion of the
replication efficiency along with adding the mirror replication overhead.
OAM Commands with EMG
There are certain limitations with using the OAM commands when egress multicast group (EMG)
is enabled. This is because OAM commands work by looping the OAM packet back to ingress
instead of sending them out of the SAP. Hence, if EMG is enabled, these OAM packets will be
looped back once per chain and hence, will only be processed for the first SAP on each chain.
Particularly, mac-ping, mac-trace and mfib-ping commands will only list the first SAP in each
chain.
Page 346 7750 SR OS Services Guide