Master-Slave Operation
Page 138 7210 SAS-X, R6 OS Services Guide
Master-Slave Operation
NOTE: 7210 SAS devices support only standby-signaling-master option. 7210 does not support
the CLI command standby-signaling-slave. In the discussion below, reference to standby-
signaling-slave command is only used to describe the solution. 7210 device can be used only
where standby-signaling-master is used in the example below.
Master-Slave pseudowire redundancy is discussed in this section. It adds the ability for the remote
peer to react to the pseudowire standby status notification, even if only one spoke-SDP terminates
on the VLL endpoint on the remote peer, by blocking the transmit (Tx) direction of a VLL spoke
SDP when the far-end PE signals standby. This solution enables the blocking of the Tx direction
of a VLL spoke SDP at both master and slave endpoints when standby is signalled by the master
endpoint. This approach satisfies a majority of deployments where bidirectional blocking of the
forwarding on a standby spoke SDP is required.
Figure 17 illustrates the operation of master-slave pseudowire redundancy. In this scenario, an
Epipe service is provided between CE1 and CE2. CE2 is dual homed to PE2 and PE3, and thus
PE1 is dual-homed to PE2 and PE3 using Epipe spoke SDPs. The objectives of this feature is to
ensure that only one pseudowire is used for forwarding in both directions by PE1, PE2 and PE3 in
the absence of a native dual homing protocol between CE2 and PE2/PE3, such as MC-LAG. In
normal operating conditions (the SAPs on PE2 and PE3 towards CE2 are both up and there are no
defects on the ACs to CE2), PE2 and PE3 cannot choose which spoke SDP to forward on based on
the status of the AC redundancy protocol.
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