vyos@r14:~$ /usr/sbin/frr_exporter --help 
usage: frr_exporter [<flags>]


Flags:
  -h, --[no-]help                Show context-sensitive help (also try --help-long and --help-man).
      --[no-]collector.bgp.peer-types  
                                 Enable the frr_bgp_peer_types_up metric (default: disabled).
      --collector.bgp.peer-types.keys=type ...  
                                 Select the keys from the JSON formatted BGP peer description of which the values will be used with the
                                 frr_bgp_peer_types_up metric. Supports multiple values (default: type).
      --[no-]collector.bgp.peer-descriptions  
                                 Add the value of the desc key from the JSON formatted BGP peer description as a label to peer metrics. (default:
                                 disabled).
      --[no-]collector.bgp.peer-groups  
                                 Adds the peer's peer group name as a label. (default: disabled).
      --[no-]collector.bgp.peer-hostnames  
                                 Adds the peer's hostname as a label. (default: disabled).
      --[no-]collector.bgp.peer-descriptions.plain-text  
                                 Use the full text field of the BGP peer description instead of the value of the JSON formatted desc key (default:
                                 disabled).
      --[no-]collector.bgp.advertised-prefixes  
                                 Enables the frr_exporter_bgp_prefixes_advertised_count_total metric which exports the number of advertised prefixes
                                 to a BGP peer. This is an option for older versions of FRR that don't have PfxSent field (default: disabled).
      --[no-]collector.bgp.accepted-filtered-prefixes  
                                 Enable retrieval of accepted and filtered BGP prefix counts (default: disabled).
      --frr.socket.dir-path="/var/run/frr"  
                                 Path of of the localstatedir containing each daemon's Unix socket.
      --frr.socket.timeout=20s   Timeout when connecting to the FRR daemon Unix sockets
      --[no-]frr.vtysh           Use vtysh to query FRR instead of each daemon's Unix socket (default: disabled, recommended: disabled).
      --frr.vtysh.path="/usr/bin/vtysh"  
                                 Path of vtysh.
      --frr.vtysh.timeout=20s    The timeout when running vtysh commands (default: 20s).
      --[no-]frr.vtysh.sudo      Enable sudo when executing vtysh commands.
      --frr.vtysh.options=""     Additional options passed to vtysh.
      --collector.ospf.instances=""  
                                 Comma-separated list of instance IDs if using multiple OSPF instances
      --[no-]collector.route.detailed-routes  
                                 Enable detailed route count of each route type (default: disabled).
      --[no-]collector.bfd       Enable the bfd collector (default: enabled, to disable use --no-collector.bfd).
      --[no-]collector.bgp       Enable the bgp collector (default: enabled, to disable use --no-collector.bgp).
      --[no-]collector.bgp6      Enable the bgp6 collector (default: disabled).
      --[no-]collector.bgpl2vpn  Enable the bgpl2vpn collector (default: disabled).
      --[no-]collector.ospf      Enable the ospf collector (default: enabled, to disable use --no-collector.ospf).
      --[no-]collector.pim       Enable the pim collector (default: disabled).
      --[no-]collector.route     Enable the route collector (default: enabled, to disable use --no-collector.route).
      --[no-]collector.vrrp      Enable the vrrp collector (default: disabled).
      --web.telemetry-path="/metrics"  
                                 Path under which to expose metrics.
      --[no-]web.systemd-socket  Use systemd socket activation listeners instead of port listeners (Linux only).
      --web.listen-address=:9342 ...  
                                 Addresses on which to expose metrics and web interface. Repeatable for multiple addresses. Examples: `:9100` or
                                 `[::1]:9100` for http, `vsock://:9100` for vsock
      --web.config.file=""       Path to configuration file that can enable TLS or authentication. See:
                                 https://github.com/prometheus/exporter-toolkit/blob/master/docs/web-configuration.md
      --log.level=info           Only log messages with the given severity or above. One of: [debug, info, warn, error]
      --log.format=logfmt        Output format of log messages. One of: [logfmt, json]
      --[no-]version             Show application version.

vyos@r14:~$

--collector.bgpl2vpn

set service monitoring prometheus frr-exporter collector bgpl2vpn

set service monitoring prometheus frr-exporter export bgpl2vpn