Port Mirroring; Mirroring Features; Remote Port Mirroring - Enterasys C3G124-24 Configuration Manual

Port Mirroring

The Enterasys C3 device allows you to mirror (or redirect) the traffic being switched on a port for
the purposes of network traffic analysis and connection assurance. When port mirroring is
enabled, one port becomes a monitor port for another port within the device (the stack, if
applicable).

Mirroring Features

The Enterasys C3 device supports the following mirroring features:
• Mirroring can be configured in a many-to-one configuration so that one target (destination)
port can monitor traffic on up to 8 source ports. Only one mirror destination port can be
configured per stack, if applicable.
• LAG ports can be a mirror source port, but not a mirror destination port. If a LAG port is a
mirror source port, no other ports can be configured as source ports.
• Both transmit and receive traffic will be mirrored.
• A destination port will only act as a mirroring port when the session is operationally active.
• When a port mirror is created, the mirror destination port is removed from the egress list of
VLAN 1 after a reboot.
• MAC addresses will be learned for packets tagged with the mirror VLAN ID. This will
prevent the ability to snoop traffic across multiple hops.

Remote Port Mirroring

Remote port mirroring is an extension to port mirroring which facilitates simultaneous mirroring
of multiple source ports on multiple switches across a network to one or more remote destination
ports.
Remote port mirroring involves configuration of the following port mirroring related parameters:
1. Configuration of normal port mirroring source ports and one destination port on all switches,
as described above.
2. Configuration of a mirror VLAN, which is a unique VLAN on which mirrored packets
traverse across the network. The mirror VLAN has to be configured on ALL switches across
the network along which mirrored traffic traverses, from the switch where the source ports
reside to the switch where the mirrored packets are sniffed and/or captured.
You must ensure that switches involved are properly configured to facilitate correct remote port
mirroring operation. The following points in particular need to be observed:
Caution: Port mirroring configuration should be performed only by personnel who are
knowledgeable about the effects of port mirroring and its impact on network operation.
Note: An Enterasys Networks Feature Guide document containing an in-depth discussion of port
mirroring configuration is located on the Enterasys Networks web site:
https://extranet.enterasys.com/downloads//
Caution: Traffic mirrored to a VLAN may contain control traffic. This may be interpreted by the
downstream neighbor as legal control frames. It is recommended that you disable any protocols
(such as Spanning Tree) on inter-switch connections that might be affected .
Port Mirroring
Enterasys C3 Configuration Guide 11-37