HP A5500 SI Switch Series Configuration Manual page 366

NOTE:
About the BS period:
By default, the BS period is determined by this formula "BS period = (BS timeout – 10) / 2". The
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default BS timeout is 130 seconds, so the default BS period = (130 – 10) / 2 = 60 (seconds).
If this parameter is manually configured, the system will use the configured value.
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About the BS timeout timer:
By default, the BS timeout value is determined by this formula "BS timeout timer = BS period × 2 +
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10". The default BS period is 60 seconds, so the default BS timeout timer = 60 × 2 + 10 = 130
(seconds).
If this parameter is manually configured, the system will use the configured value.
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CAUTION:
Be sure to configure the BS period smaller than the BS timeout value.
Disabling BSM semantic fragmentation
Generally, a BSR periodically distributes the RP-set information in bootstrap messages within the IPv6
PIM-SM domain. It encapsulates a BSM in an IPv6 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
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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
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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 and learn only part of the RP-set information. Therefore, if
such devices exist in the IPv6 PIM-SM 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...
Enter system view
Enter IPv6 PIM view
Disable the BSM semantic
fragmentation function
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 IPv6 PIM neighbor
is performed according to the MTU of the outgoing interface.
Use the command...
system-view
pim ipv6
undo bsm-fragment enable
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Remarks
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Required
By default, the BSM semantic
fragmentation function is enabled.