Remote Mirroring Considerations And Restrictions - Avaya 8800 Troubleshooting Manual

Troubleshooting tool fundamentals

Remote mirroring considerations and restrictions

Mirrored traffic shares ingress, egress, and fabric bandwidth with normal traffic and can impact
normal traffic. Therefore, only enable these features for troubleshooting, debugging, or for
security purposes such as packet sniffing, intrusion detection, or intrusion prevention.
To support remote mirroring, all the nodes in the network must be able to handle a packet size
up to 1542 bytes.
The following limitations apply to remote mirroring:
• You can configure a maximum of 16 RMTs in a switch.
• Only one port of an OctaPID can act as an RMT.
• Only one port in an OctaPID can act as an RMS.
• On R modules, you can mirror only one port in each egress lane. This does not apply to
RS/8800 modules.
• The RMS port must be a port mirroring destination port because only mirrored packets
are remote mirrored. The switch does not check if the port is a port mirroring destination
port, and does not send error messages if it is not.
• An RMT must be part of at least one port-based VLAN.
Be aware of the following information:
• If the RMS is a tagged port, the mirrored packet is encapsulated and transmitted with the
VLAN ID of the RMS port and forwarded to the RMT. Encapsulation does not modify the
mirrored packet data or the VLAN ID. When the RMT port receives an encapsulated frame
from the switch fabric, the port removes the remote mirroring encapsulation and the frame
is transmitted on the port with the VLAN ID of the mirrored packet (the original packet).
• If port mirroring is disabled, no packets are remote mirrored.
• Packets are captured only when the RMT is reachable.
• When you enable or disable remote mirroring, a trap is sent to the trap receiver, and an
SNMP log message states that remote mirroring is enabled or disabled and the mode.
• When you remove an I/O module from a slot, the RMS and the RMT on all ports in the
slot are disabled. This action generates an SNMP log message and a trap. When you
reinsert the module, the RMS and RMT are reenabled, but you must re-enable remote
mirroring.
• The RMT switch can receive the remote mirroring packet with complete remote mirroring
encapsulation (including the remote mirroring tag).
• Remote mirrored packets are sent with lowest priority (that is, a p-bit value of 0).
• When the RMT port is used for local port and remote port mirroring, the sniffer can't
decode the mirrored traffic and reports them as malformed packets. When the RMT port
is used for a remote port mirror or a local port mirror, the sniffer can decode the mirrored
36 Troubleshooting
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July 2013