Mirror Implementation; Mirror Source And Destinations - Alcatel-Lucent 7750 SR OS Service Manual

Service Mirroring

Mirror Implementation

Mirroring can be implemented on ingress or egress service access points (SAPs) or ingress and
egress network interfaces. The Flexible Fast Path processing complexes preserve the ingress
packet throughout the forwarding and mirroring process, making incremental packet changes on a
separate copy.
Alcatel-Lucent's implementation of packet mirroring is based on two assumptions:
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Mirror Source and Destinations

Mirror sources and destinations have the following characteristics:
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Ingress and egress packets are mirrored as they appear on the wire. This is important for
troubleshooting encapsulation and protocol issues.
→ When mirroring at ingress, the Flexible Fast Path network processor array (NPA)
sends an exact copy of the original ingress packet to the mirror destination while
normal forwarding proceeds on the original packet.
→ When mirroring is at egress, the NPA performs normal packet handling on the egress
packet, encapsulating it for the destination interface. A copy of the forwarded packet
(as seen on the wire) is forwarded to the mirror destination.
Mirroring must support tunnel destinations.
→ Remote destinations are reached by encapsulating the ingress or egress packet within
an SDP, like the traffic for distributed VPN connectivity services. At the remote
destination, the tunnel encapsulation is removed and the packet is forwarded out a
local SAP.
They can be on the same 7750 SR router (local) or on two different routers (remote).
Mirror destinations can terminate on egress virtual ports which allows multiple mirror
destinations to send to the same packet decode device, delimited by IEEE 802.1Q
(referred to as dot1q) tags. This is helpful when troubleshooting a multi-port issue within
the network.
When multiple mirror destinations terminate on the same egress port, the individual dot1q
tags can provide a DTE/DCE separation between the mirror sources.
Packets ingressing a port can have a mirror destination separate from packets egressing
another or the same port (the ports can be on separate nodes).
A total of 255 mirror destinations are supported (local and/or remote), per chassis.
7750 SR OS Services Guide