Effect Of Downstream Vlan Tagging On Untagged, Mirrored Traffic; Operating Notes - ProCurve 6200yl Management And Configuration Manual

Monitoring and Analyzing Switch Operation
Traffic Mirroring
B-70
Effect of Downstream VLAN Tagging on
Untagged, Mirrored Traffic
In a remote mirroring application, if mirrored traffic leaves the switch without
802.1Q VLAN tagging, but is forwarded through a downstream device that adds
802.1Q VLAN tags, then the MTU for untagged, mirrored frames leaving the
source switch is reduced below the values shown in table B-2. That is, if the
MTU on the path to the destination is 1522 bytes, then untagged, mirrored
frames leaving the source switch cannot exceed 1518 bytes. If the MTU on the
path to the destination is 9220 bytes, then untagged, mirrored frames leaving
the source switch cannot exceed 9216 bytes.
Tagged 10 Gbps VLAN link.
Adds 4 bytes to each frame.
6200yl
Aggregator
Untagged 1 Gbps
VLAN Links
3500yl
Mirror Source
Figure B-36. Effect of Downstream VLAN Tagging on the MTU for Mirrored Traffic

Operating Notes

Mirroring Dropped Traffic: Where an interface is configured to mirror-
■
ing traffic to a destination, it does so regardless of whether the traffic is
dropped while on the interface. For example, if an ACL configured on a
VLAN with a deny ACE that eliminates packets from a Telnet application,
the switch still mirrors the Telnet packets it receives on the interface and
subsequently drops.
Router in the
Mirror Path
3500yl
Mirror Source
Due to VLAN tagging on the 10 Gbps link,
untagged traffic from the mirror sources must
be at least 4 bytes smaller than the MTU for
the path to the mirror destination.
5400zl
Remote
1Gbps
Mirror
Destination
Traffic
Analyzer