The mapping server feature configures and advertises, in OSPF, of the node SID index for prefixes of routers which are in the LDP domain. This is performed in the router acting as a mapping server and using a prefix-SID sub-TLV within an OSPF Extended Prefix Range TLV.
Use the following command syntax to configure the SR mapping database in OSPF:
configure
— router
— [no]ospf
— segment-routing
— no segment-routing
— mapping-server
— sid-map node-sid {index value 0 to 4294967295 [range value 1 to 65535]} prefix {{ip-address/mask}|{netmask}}[scope {area area-id | as}]
— no sid-map node-sid index value
The user enters the node SID index, for one prefix or a range of prefixes, by specifying the first index value and, optionally, a range value. The default value for the range option is 1. Only the first prefix in a consecutive range of prefixes must be entered. If the user enters the first prefix with a mask lower than 32, the OSPF Extended Prefix Range TLV is advertised but a router that receives the OSPF Extended Prefix Range TLV does not resolve the SID and instead generates a trap.
The no form of the sid-map command deletes the range of node SIDs beginning with the specified index value. The no form of the mapping-server command deletes all node SID entries in the OSPF instance.
Use the scope option to specify the flooding scope of the mapping server for the generated OSPF Extended Prefix Range TLV. There is no default value. If the scope is a specific area, the TLV is flooded only in that area.
An ABR that propagates an intra-area OSPF Extended Prefix Range TLV flooded by the mapping server in that area into other areas sets the inter-area flag (IA-flag). The ABR also propagates the TLV if it is received with the inter-area flag set from other ABR nodes but only from the backbone to leaf areas and not leaf areas to the backbone. However, if the identical TLV was advertised as an intra-area TLV in a leaf area, the ABR does not flood the inter-area TLV into that leaf area.
Each time a prefix or a range of prefixes is configured in the SR mapping database in any routing instance, the router issues for this prefix, or range of prefixes, a prefix-SID sub-TLV within an OSPF Extended Prefix Range TLV in that instance. The flooding scope of the TLV from the mapping server is determined as previously described. The reachability of that prefix in the mapping server route table is not checked. Additionally, the SR OS does not check whether the SID index is a duplicate of an existing prefix in the local IGP instance database or if the SID index is out of range with the local SRGB.