H3C Technologies H3C S12500 Series Switches - Manual (Page 407)

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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.
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.
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 PIM-SM domain, you need to disable the semantic fragmentation function
on the C-BSRs.
To disable the BSM semantic fragmentation function:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter IPv6 PIM view. pim ipv6 N/A
3. Disable the BSM semantic
fragmentation function.
undo bsm-fragment enable
By default, the BSM semantic
fragmentation function is enabled.
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-scoped zones. Each IPv6 admin-scoped zone
maintains a BSR to provide services for a specific IPv6 multicast group range. The IPv6 global-scoped
zone also maintains a BSR to provide services for the IPv6 multicast groups with the Scope field in the
group addresses being 14.
Enabling IPv6 administrative scoping
Before you configure an IPv6 admin-scoped zone, you must enable IPv6 administrative scoping first.
Perform the following configuration on all routers in the IPv6 PIM-SM domain.
To enable IPv6 administrative scoping:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter IPv6 PIM view. pim ipv6 N/A
3. Enable IPv6 administrative
scoping.
c-bsr admin-scope Disabled by default.