The simplest form of pseudowire redundancy is to configure pseudowire with active
and standby remote PE IP addresses. If the pseudowire to the primary remote PE fails
(either because the remote PE has failed or because there is no LSP to the remote PE),
then the local PE will establish a pseudowire to the standby remote PE instead.
However, establishing a pseudowire takes time (for LDP signalling, etc.), so a better
model is to preestablish the pseudowire to the standby PE and then use PW status
signalling to switch between active and standby remote PEs. An additional status bit
has been defined in the status code signaled by the PW status TLV to enable the PE
to signal PW status as ???active??? or ???standby.??? If one or both PE devices at either end of
a pseudowire signal a status of standby, then neither PE will send any data over the
pseudowire (though they may send OAM messages).
One very useful model for pseudowire redundancy, as shown in Figure 14.5, is one
where the local PE sets up pseudowires to a pair of remote PEs that connect to a
single CE device using a multi-chassis Layer 2 redundancy protocol (e.g., multi-chassis
802.
Pages:
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996