Chapter 4: Troubleshooting Fundamentals; Port Mirroring; Port Mirroring Limitations - Avaya ERS 2500 Series Troubleshooting Manual

Chapter 4: Troubleshooting fundamentals

This section describes available troubleshooting tools and their applications.

Port mirroring

Avaya Ethernet Routing Switch 2500 Series switches have a port mirroring feature that helps
you to monitor and analyze network traffic. The port mirroring feature supports both ingress
(incoming traffic) and egress (outgoing traffic) port mirroring. When port mirroring is enabled,
the ingress or egress packets of the mirrored (source) port are forwarded normally and a copy
of the packets is sent from the mirrored port to the mirroring (destination) port.
You can observe and analyze packet traffic at the mirroring port using a network analyzer. A
copy of the packet can be captured and analyzed. Unlike other methods that are used to
analyze packet traffic, the packet traffic is uninterrupted and packets flow normally through the
mirrored port.

Port mirroring limitations

The Ethernet Routing Switch 2500 Series supports port mirroring in the following three modes:
• ingress mode (XRX or ->Port X)
• egress mode (XTX or Port X ->)
• ingress and egress mode (XRX or XTX or <->Port X)
There are limitations to the egress mode. As a standalone unit or in a stack, port-mirroring
mode XTX mirrors egress traffic on the mirrored port, but does not mirror control packets
generated by the switch. The monitor port does not receive copies of the generated control
packets that egress from the mirrored port.
There are also limitations to the ingress and egress mode. First, the same limitation on the
XTX portion also applies to the ingress and egress mode. Second, Avaya recommends that
the monitor port and the mirror port be on the same unit in a stack.
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