Virtual Private LAN Services
7210 SAS M Services Guide Page 279
MAC Flush Message Processing
The previous sections described operation principle of several redundancy mechanisms available
in context of VPLS service. All of them rely on MAC flush message as a tool to propagate
topology change in a context of the given VPLS. This section aims to summarize basic rules for
generation and processing of these messages.
As described on respective sections, the 7210 SAS supports two types of MAC flush message,
flush-all-but-mine and flush-mine. The main difference between these messages is the type of
action they signal. Flush-all-but-mine requests clearing of all FDB entries which were learned
from all other LDP peers except the originating PE. This type is also defined by RFC 4762 as an
LDP MAC address withdrawal with an empty MAC address list.
Flush-all-mine message requests clearing all FDB entries learned from originating PE. This means
that this message has exactly other effect then flush-all-but-mine message. This type is not
included in RFC 4762 definition and it is implemented using vendor specific TLV.
The advantages and disadvantages of the individual types should be apparent from examples in the
previous section. The description here focuses on summarizing actions taken on reception and
conditions individual messages are generated.
Upon reception of MAC flush messages (regardless the type) SR-Series PE will take following
actions:
• Clears FDB entries of all indicated VPLS services conforming the definition.
• Propagates the message (preserving the type) to all LDP peers, if “propagate-mac-flush”
flag is enabled at corresponding VPLS level.
The flush-all-but-mine message is generated under following conditions:
• The flush-all-but-mine message is received from LDP peer and propagate-mac-flush flag
is enabled. The message is sent to all LDP peers in the context of VPLS service it was
received in.
• TCN message in a context of STP instance is received. The flush-all-but-mine message is
sent to all LDP-peers connected with spoke and mesh SDPs in a context of VPLS service
controlled by the given STP instance (based on mVPLS definition). The message is sent
only to LDP peers which are not part of STP domain, which means corresponding spoke
and mesh SDPs are not part of mVPLS.
• Flush-all-but-mine message is generated when switch over between spoke SDPs of the
same endpoint occurs. The message is sent to LDP peer connected through newly active
spoke SDP.
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