A BIER template can be created under the config>router context and provides a centralized BIER configuration where the operator can configure all the BIER parameters. The BIER template contains the sub-domain to multi-topology mapping and other BIER configurations, such as the BFR ID and BIER prefix.
Each sub-domain can contain a single IGP multi-topology (MT). Currently, SR OS only supports MT for IS-IS but not for OSPF.
A BIER template can contain many MTs and SDs. Each SD has its own BIER prefix and BFR ID and can belong to a different MT. The default MT is ipv4-unicast MT.
An example BIER template:
*A:swsim100_a>config>router>bier>template# info
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sub-domain 0
prefix 100.0.0.100
bfr-id 4096
exit
sub-domain 1
prefix 100.0.0.101
bfr-id 1
mt ipv4-multicast
exit
no shutdown
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After a template is configured it can be assigned to a corresponding IGP protocol. The IGP protocol chooses the first <SD, MT> that matches its own configured MT. For example, if the IS-IS has an MT of IPv4-multicast for the example BIER template, it uses the sub-domain 1 configuration. It builds its BIER forwarding table base on SD 1 SI, BSL and use the BIER prefix configured under sub-domain 1 for its IGP sub-TLVs.