Juniper EX9200 Features Manual page 83

Copyright © 2016, Juniper Networks, Inc.
The BGP designated VE device-selection procedure is as follows:
If the advertisement has the down bit set to 0, the advertisement is discarded.
1.
Select the path with a higher preference. The preference attribute is obtained from
2.
the site-preference configured using the
routing-instances routing-instance-name protocols vpls site site-name] hierarchy
level. If the site-preference is 0, the preference attribute is obtained from the
local-preference.
If the preference values are the same, select the path with the lower router-id.
3.
If the router-ids are the same, the routes are from the same PE router and the
4.
advertisement is considered to be an update.
Once the BGP designated VE device-selection procedure is complete, the VPLS
designated VE device-selection procedure begins. This procedure is carried out regardless
of the outcome of the BGP designated VE device-selection procedure:
If the advertisement has the down bit set to 0, the advertisement is discarded.
1.
Select the path with a higher preference. The preference attribute is obtained from
2.
the site-preference configured using the
routing-instances routing-instance-name protocols vpls site site-name] hierarchy
level. If the site-preference is 0, the preference attribute is obtained from the
local-preference.
If the preference values are the same, select the path with the lower router-id.
3.
If the router-ids are the same, select the path with a lower route distinguisher.
4.
If the route distinguishers are the same, select the path with the lower block offset
5.
value.
If the block offset values are the same, the advertisement is considered to be an
6.
update.
Once the BGP and VPLS path selection procedures have been completed and the
designated VE devices have been selected, a pseudowire can be created between the
remote PE router and the multihomed PE router.
When the remote PE router establishes or refreshes a pseudowire to the local PE router,
it verifies that the prefix is in the range required for the site ID based on the block offset
and label range advertised by the designated VE device. If the prefix is out of range, the
pseudowire status is set to out of range.
The following cases outline the potential decisions that could be made when a PE router
completes the BGP and VPLS path selection procedures for a Layer 2 advertisement in
the VPLS network:
The PE router originated one of the multihomed advertisements and selected its own
advertisement as the best path.
This PE router has been selected as the designated VE device. Selection as the
designated VE device triggers the creation of pseudowires to and from the other PE
Chapter 7: Configuring Multihoming
site-preference statement at the [edit
statement at the [edit
site-preference
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