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Disabling BSM semantic fragmentation
Generally, a BSR periodically distributes the RP-set information in bootstrap messages within the IPv6
BIDIR-PIM domain. It encapsulates a BSM in an IP datagram and might split the datagram into fragments
if the message exceeds the maximum transmission unit (MTU). In respect of such IP fragmentation, loss of
a single IP fragment leads to unavailability of the entire message.
Semantic fragmentation of BSMs can solve this issue. When a BSM exceeds the MTU, it is split to
multiple bootstrap message fragments (BSMFs).
•
Upon receiving a BSMF that contains the RP-set information of one group range, a non-BSR router
updates corresponding RP-set information directly.
•
If the RP-set information of one group range is carried in multiple BSMFs, a non-BSR router updates
corresponding RP-set information upon receiving all these BSMFs.
Because the RP-set information contained in each segment is different, loss of some IP fragments will not
result in dropping of the entire message.
The function of BSM semantic fragmentation is enabled by default. Devices not supporting this function
might deem a fragment as an entire message, thus learning only part of the RP-set information.
Therefore, if such devices exist in the IPv6 BIDIR-PIM domain, you need to disable the semantic
fragmentation function on the C-BSRs.
Follow these steps to disable the BSM semantic fragmentation function:
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enter IPv6 PIM view
pim ipv6
—
Disable the BSM semantic
fragmentation function
undo bsm-fragment
enable
Required
By default, the BSM semantic
fragmentation function is enabled.
NOTE:
Generally, a BSR performs BSM semantic fragmentation according to the MTU of its BSR interface.
However, the semantic fragmentation of BSMs originated due to learning of a new PIM neighbor is
performed according to the MTU of the outgoing interface.
Configuring IPv6 administrative scoping
With administrative scoping disabled, an IPv6 BIDIR-PIM domain has only one BSR. The BSR manages
the whole network. To manage your network more effectively and specifically, partition the IPv6 BIDIR-
PIM domain into multiple admin-scope zones. Each admin-scope zone maintains a BSR, which serves a
specific multicast group range, and the global scope zone also maintains a BSR, which serves all the
rest multicast groups.
Enabling IPv6 administrative scoping
Before you configure an IPv6 admin-scope zone, you must enable IPv6 administrative scoping first.
Perform the following configuration on routers that can become a C-BSR and ZBR.
Follow these steps to enable administrative scoping:
Summary of Contents for A5500 EI Switch Series
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