BMP

BMP (BGP Monitoring Protocol, RFC 7854) is used to send monitoring data from BGP routers to network management entities.

Implementation characteristics

The BMP implementation in FRR has the following properties:

  • only the RFC 7854 features are currently implemented. This means protocol version 3 without any extensions. It is not possible to use an older draft protocol version of BMP.

  • the following statistics codes are implemented:

    • 0: count of prefixes rejected
    • 2: count of duplicate prefix withdrawals
    • 3: count of prefixes with loop in cluster id
    • 4: count of prefixes with loop in AS-path
    • 5: count of prefixes with loop in originator
    • 11: count of updates subjected to RFC 7607 "treat as withdrawal" handling due to errors
    • 65531: experimental count of prefixes rejected due to invalid next-hop

    Note that stat items 3, 4 and 5 are specified to count updates, but FRR implements them as prefix-based counters.

  • route mirroring is fully implemented, however BGP OPEN messages are not currently included in route mirroring messages. Their contents can be extracted from the "peer up" notification for sessions that established successfully. OPEN messages for failed sessions cannot currently be mirrored.

  • route monitoring is available for IPv4 and IPv6 AFIs, unicast and multicast SAFIs. Other SAFIs (VPN, Labeled-Unicast, Flowspec, etc.) are not currently supported.

  • monitoring peers that have BGP add-path enabled on the session will result in somewhat unpredictable behaviour. Currently, the outcome is:

    • route mirroring functions as intended, messages are copied verbatim
    • the add-path ID is never included in route monitoring messages
    • if multiple paths were received from a peer, an unpredictable path is picked and sent on the BMP session. The selection will differ for pre-policy and post-policy monitoring sessions.
    • as long as any path is present, something will be advertised on BMP sessions. Only after the last path is gone a withdrawal will be sent on BMP sessions.
    • updates to additional paths will trigger BMP route monitoring messages. There is no guarantee on consistency regarding which path is sent in these messages.

  • monitoring peers with RFC 5549 extended next-hops has not been tested.

Starting BMP

BMP is implemented as a loadable module. This means that to use BMP, bgpd must be started with the -M bmp option. It is not possible to enable BMP if bgpd was started without this option.

Configuring BMP

All of FRR's BMP configuration options are located inside the router bgp ASN block. Configure BGP first before proceeding to BMP setup.

There is one option that applies to the BGP instance as a whole:

bmp mirror buffer-limit(0-4294967294)

This sets the maximum amount of memory used for buffering BGP messages (updates, keepalives, ...) for sending in BMP Route Mirroring.

The buffer is for the entire BGP instance; if multiple BMP targets are configured they reference the same buffer and do not consume additional memory. Queue overhead is included in accounting this memory, so the actual space available for BGP messages is slightly less than the value configured here.

If the buffer fills up, the oldest messages are removed from the buffer and any BMP sessions where the now-removed messages were still pending have their entire queue flushed and a "Mirroring Messages Lost" BMP message is sent.

BMP Route Monitoring is not affected by this option.

All other configuration is managed per targets:

bmp targets NAME

Create/delete a targets group. As implied by the plural name, targets may cover multiple outbound active BMP sessions as well as inbound passive listeners.

If BMP sessions have the same configuration, putting them in the same bmp targets will reduce overhead.

BMP session configuration

Inside a bmp targets block, the following commands control session establishment:

bmp connect HOSTNAME port (1-65535) {min-retry MSEC|max-retry MSEC}

Add/remove an active outbound BMP session. HOSTNAME is resolved via DNS, if multiple addresses are returned they are tried in nondeterministic order. Only one connection will be established even if multiple addresses are returned. min-retry and max-retry specify (in milliseconds) bounds for exponential backoff.

Warning

ip access-list and ipv6 access-list are checked for outbound connections resulting from bmp connect statements.

bmp listener <X:X::X:X|A.B.C.D> port (1-65535)

Accept incoming BMP sessions on the specified address and port. You can use 0.0.0.0 and :: to listen on all IPv4/IPv6 addresses.

ip access-list NAME
ipv6 access-list NAME

Restrict BMP sessions to the addresses allowed by the respective access lists. The access lists are checked for both passive and active BMP sessions. Changes do not affect currently established sessions.

BMP data feed configuration

The following commands configure what BMP messages are sent on sessions associated with a particular bmp targets:

bmp stats [interval (100-86400000)]

Send BMP Statistics (counter) messages at the specified interval (in milliseconds.)

bmp monitor AFI SAFI <pre-policy|post-policy>

Perform Route Monitoring for the specified AFI and SAFI. Only IPv4 and IPv6 are currently valid for AFI, and only unicast and multicast are valid for SAFI. Other AFI/SAFI combinations may be added in the future.

All BGP neighbors are included in Route Monitoring. Options to select a subset of BGP sessions may be added in the future.

bmp mirror

Perform Route Mirroring for all BGP neighbors. Since this provides a direct feed of BGP messages, there are no AFI/SAFI options to be configured.

All BGP neighbors are included in Route Mirroring. Options to select a subset of BGP sessions may be added in the future.