H3C Technologies H3C S10500 Series Switches - Manual (Page 396)

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CAUTION:
In configuration, make sure that the BS period is 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).
• After 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 after 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… 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 IPv6 PIM neighbor is
performed according to the MTU of the outgoing interface.
Configuring IPv6 administrative scoping
With IPv6 administrative scoping disabled, an IPv6 PIM-SM domain has only one BSR. The BSR
manages the whole network. To manage your network more effectively and specifically, you can
partition the IPv6 PIM-SM domain into multiple IPv6 admin-scope zones. Each IPv6 admin-scope zone
maintains a BSR, which serves a specific IPv6 multicast group range. The IPv6 global scope zone also
maintains a BSR, which serves the IPv6 multicast groups with the Scope field in the group addresses
being 14.
Enabling IPv6 administrative scoping
Before you configure an IPv6 admin-scope zone, you must enable IPv6 administrative scoping.