banshee/network-collection/network/snmp/bgp-peers

BGP peers of a router, by SNMP

Returns, for each BGP peer of a router, the state of its session, the AS of the peer, how long the session has been established, and how many times it has come up. Four watches are offered: a session down, a session that flaps, a session established recently, and a peer missing.

Versions

Generic: any router whose agent serves BGP4-MIB, whatever its brand. A router without BGP, or that does not serve it, stops the collector as misconfigured.

How it works

The collector reads bgpPeerTable (BGP4-MIB, RFC 4273). A peer is named by its address (192.0.2.1).

The state is bgpPeerState in words: idle, connect, active, opensent, openconfirm, established. A peer the administrator has shut (bgpPeerAdminStatus stop) reads stopped, so that it does not pass for a peer that fell.
"Session down" is critical for any state other than established and stopped.
The time established is bgpPeerFsmEstablishedTime, in minutes, for an established session only.
The times established is bgpPeerFsmEstablishedTransitions, a counter of the times the session came up: "Session flapping" raises when it grows by more than 2 in an hour.

The collector only reads: SNMP sends nothing but reads.

Prerequisites

The SNMP agent of the router enabled, reachable from the poller (UDP 161), its access restricted to the poller.
The view granted to the poller includes bgp (.1.3.6.1.2.1.15).
Read-only access, SNMPv2c or SNMPv3, set on the host or one of its folders (protocol:snmp:* variables).

Outputs

Name	Label	Unit	Per instance
`state`	Session state	—	yes, per peer
`remote-as`	Remote AS	—	yes, per peer
`established-for`	Time established	min	yes, per peer
`established-count`	Times established	—	yes, per peer

Watches

Name	Title	Kind	Defaults	Checked by default
`down`	Session down	expected value, on `state`	critical when the state is neither `established` nor `stopped`	yes
`flapping`	Session flapping	increase, on `established-count`	warning beyond 2 in 1 h	yes
`recently-established`	Session established recently	below a threshold, on `established-for`	warning below 15 min	no
`missing`	Peer missing	expected instances, on `state`	no peer named: it raises nothing until addresses are set on the probe	no

Limits

BGP4-MIB lists IPv4 peers only: an IPv6 peer is not seen. Its successor, BGP4-V2-MIB, is a draft that each vendor serves under its own number.
BGP4-MIB counts no prefixes: the prefixes received from a peer are in each vendor's MIB (CISCO-BGP4-MIB, the Juniper and Arista ones), not read here.
A router with several routing instances (VRF) usually lists in BGP4-MIB only the peers of its default instance.
A peer removed from the configuration leaves the table: only "Peer missing" sees it.
An empty table stops the collector misconfigured, where network/snmp/ospf-neighbors raises "No neighbor": a configured BGP peer stays in the table when its session is down, so an empty table means a router without BGP or a view without BGP4-MIB, whereas OSPF neighbors leave their table when they fall.