Routers with PBB-EVPN services use the following route types to advertise the ISID of a specific service.
Inclusive Multicast Ethernet Tag routes (IMET-ISID routes) are used to auto-discover ISIDs in the PBB-EVPN network. The routes encode the service ISID in the Ethernet Tag field.
BMAC-ISID routes are only used when ISID-based C-MAC flush is configured. The routes encode the ISID in the Ethernet Tag field.
Although the preceding routes are only relevant for routers where the advertised ISID is configured, they are sent with the B-VPLS route-target by default. As a result, the routes are unnecessarily disseminated to all the routers in the B-VPLS network.
SR OS supports the use of per-ISID or group of ISID route-targets, which limits the dissemination of IMET-ISID or BMAC-ISID routes for a specific ISID to the PEs where the ISID is configured.
The config>service>(b-)vpls>isid-route-target>isid-range from [to to] [auto-rt | route-target rt] command allows the user to determine whether the IMET-ISID and BMAC-ISID routes are sent with the B-VPLS route-target (default option, no command), or a route-target specific to the ISID or range of ISIDs.
The following configuration example shows how to configure ISID ranges as auto-rt or with a specific route-target.
*A:PE-3>config>service>(b-)vpls>bgp-evpn#
isid-route-target
[no] isid-range <from> [to <to>] {auto-rt|route-target <rt>}
/* For example:
*A:PE-3>config>service>(b-)vpls>bgp-evpn#
isid-route-target
isid-range 1000 to 1999 auto-rt
isid-range 2000 route-target target:65000:2000
The auto-rt option auto-derives a route-target per ISID in the following format:
<2-byte-as-number>:<4-byte-value>
Where: 4-byte-value = 0x30+ISID, as described in RFC 7623. Figure 1 shows the format of the auto-rt option.
Where:
If it is 2 bytes, then the AS number is obtained from the config>router>autonomous-system command. If the AS number exceeds the 2 byte limit, then the low order 16-bit value is used.
A = 0 for auto-derivation
Type = 3, which corresponds to an ISID-type route-target
ISID is the 24-bit ISID
The type and sub-type are 0x00 and 0x02.
If isid-route-target is enabled, the export and import directions for IMET-ISID and BMAC-ISID route processing are modified as follows.
Exported IMET-ISID and BMAC-ISID routes
For local I-VPLS ISIDs and static ISIDs, IMET-ISID routes are sent individually with an ISID-based route-target (and without a B-VPLS route-target) unless the ISID is contained in an ISID policy for which no advertise-local is configured.
If both isid-route-target and send-bvpls-evpn-flush options are enabled for an I-VPLS, the BMAC-ISID route is also sent with the ISID-based route-target and no B-VPLS route-target.
The isid-route-target command affects the IMET-ISID and BMAC-ISID routes only. The BMAC-0, IMET-0 (B-MAC and IMET routes with Ethernet Tag == 0), and ES routes are not impacted by the command.
Imported IMET-ISID and BMAC-ISID routes
Upon enabling isid-route-target for a specific I-VPLS, the BGP starts importing IMET-ISID routes with ISID-based route-targets, and (assuming the bgp-evpn accept-ivpls-evpn-flush option is enabled) BMAC-ISID routes with ISID-based route-targets.
The new ISID-based RTs are added for import operations when the I-VPLS is associated with the B-VPLS service (and not based on the I-VPLS operational status), or when the static-isid is added.
The system does not maintain a mapping of the route-targets and ISIDs for the imported routes. For example, if I-VPLS 1 and 2 are configured with the isid-route-target option and IMET-ISID=2 route is received with a route-target corresponding to ISID=1, then BGP imports the route and the router processes it.
The router does not check the format of the received auto-derived route-targets. The route is imported as long as the route-target is on the list of RTs for the B-VPLS.
If the isid-route-target option is configured for one or more I-VPLS services, the vsi-import and vsi-export policies are blocked in the B-VPLS. BGP peer import and export policies are still allowed. Matching on the export ISID-based route-target is supported.