BGP-based auto-discovery is performed by a multicast VPN address family. Any PE that attaches to an MVPN must issue a BGP update message containing an NLRI in this address family, along with a specific set of attributes.
The PE router uses route targets to specify MVPN route import and export. The route target may be the same as the one used for the corresponding unicast VPN, or it may be different. The PE router can specify separate import route targets for sender sites and receiver sites for a specific MVPN.
The route distinguisher (RD) that is used for the corresponding unicast VPN can also be used for the MVPN.
When BGP auto-discovery is enabled, PIM peering on the I-PMSI is disabled, so no PIM hellos are sent on the I-PMSI. C-trees to P-tunnels bindings are also discovered using BGP S-PMSI AD routes, instead of PIM join TLVs. Configure PIM join TLVs when c-mcast-signaling is set to pim in the config>service>vprn>mvpn>provider-tunnel>selective>auto-discovery-disable context.
Table: Supported configuration combinations and Table: Supported configuration combinations describe the supported configuration combinations. If the CLI combination is not allowed, the system returns an error message. If the CLI command is marked as ‟ignored” in the table, the configuration is not blocked, but its value is ignored by the software.
| Auto-discovery | Inclusive PIM SSM | Action |
|---|---|---|
Yes |
Yes |
Allowed |
MDT-SAFI |
Yes |
Allowed |
No |
Yes |
Not Allowed |
Yes or No |
No |
Allowed |
MDT-SAFI |
No |
Ignored |
MDT-SAFI |
No (RSVP and MLDP) |
Not Allowed |
| Auto-discovery | C-mcast-signaling | s-PMSI auto-discovery | Action |
|---|---|---|---|
Yes |
BGP |
Ignored |
Allowed |
Yes |
PIM |
Yes |
Allowed |
Yes |
PIM |
No |
Allowed |
No |
BGP |
Ignored |
Not Allowed |
No |
PIM |
Ignored |
Allowed |
MDT-SAFI |
Ignored (PIM behavior) |
Ignored (‟No” behavior) |
Allowed |
For example, if auto-discovery is disabled, the c-mcast-signaling bgp command fails with an error message stating:
C-multicast signaling in BGP requires auto-discovery to be enabled
If c-mcast-signaling is set to bgp then no auto-discovery fails with an error message stating
C-multicast signaling in BGP requires auto-discovery to be enabled
When c-mcast-signaling is set to bgp, S-PMSI A-D is always enabled (its configuration is ignored);
When auto-discovery is disabled, S-PMSI A-D is always disabled (its configuration is ignored).
When auto-discovery is enabled and c-multicast-signaling is set to pim, the S-PMSI A-D configuration value is used.
mdt-safi uses pim c-mcast-signaling and s-pmsi-signaling regardless of what is configured. A c-mcast-signaling or s-pmsi-signaling configuration is ignored, but both pim and bgp values are allowed.
mdt-safi is only applicable to PIM-SSM I-PMSI. PIM-SM (ASM) I-PMSI is configurable but is ignored. RSVP and MLDP I-PMSI are not allowed.
MVPN implementation based on RFC 6037, Cisco Systems’ Solution for Multicast in MPLS/BGP IP VPNs can support membership auto-discovery using BGP MDT-SAFI. A CLI option is provided per MVPN instance to enable auto-discovery either using BGP MDT-SAFI or NG-MVPN. Only PIM-MDT is supported with BGP MDT-SAFI method.