Juniper JUNOSE 11.0.X MULTICAST ROUTING, Configuration Manual

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For example, an ERX1440 Broadband Services Router has tunnel-service modules
installed in slots 4, 9, and 12. Using the load-balancing mechanism, the router
determines that the SM in slot 4 can accommodate the first bundled session for
MLPPP bundle A, and places it there. The first bundled session for bundle A has an
endpoint discriminator of 5. The router subsequently places all bundled sessions for
bundle A (which have an endpoint discriminator of 5) on the SM in slot 4.
When the SM on which the bundled sessions reside has no more space for additional
sessions, the router refuses the L2TP session. This can happen even when other
tunnel-service modules installed in the router have available space.
For more information about endpoint discriminators, see the Configuring Multilink
PPP chapter in JUNOSe Link Layer Configuration Guide .
Assigning Bundled Group Identifiers
In some cases, an endpoint discriminator is not available for the LNS to use to identify
the links in a bundled session.
This situation might occur when:
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PPP clients provide endpoint discriminators with null values.
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PPP clients do not provide an endpoint discriminator option when negotiating
LCP with the LAC.
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The LAC does not include a endpoint discriminator option in the LCP proxy AVPs.
The router places all bundled sessions without endpoint discriminators on the same
SM. However, if there are many such bundled sessions, the load-balanced distribution
of LNS sessions across the tunnel-service modules can deteriorate because the router
places all bundled sessions on the same SM without evenly distributing the load.
The bundled-group-id command enables you to correct this situation by assigning
a numeric bundled group identifier for the router to use when the endpoint
discriminator is unavailable to identify the bundled membership. The router places
bundled sessions with the same bundled group identifier on the same SM in the same
way that it does with endpoint discriminators.
The bundled group identifier applies to the entire router; therefore, if you assign the
same bundled group identifier for different L2TP destination host profiles, the router
places all of the bundled sessions with the same bundled group identifier on the
same SM.
NOTE: We recommend that you assign bundled group identifiers only when you are
certain that endpoint discriminators are unavailable to identify bundle membership.
■
To assign a numeric bundled group identifier:
host1:boston(config-l2tp-dest-profile-host)# bundled-group-id 4
Selecting Tunnel-Service Modules for LNS Sessions Using MLPPP
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Chapter 13: Configuring an L2TP LNS