OpenBGPD

OpenBGPD

Synopsis #

This chapter provides canonical, production-focused patterns for running BGP on OpenBSD using the base system daemon bgpd(8) . It covers configuration in bgpd.conf(5) , runtime operations with bgpctl(8) , service control via rcctl(8) , and optional origin validation with rpki-client(8) . These patterns apply to external peering, multi-provider edges, iBGP within a site or POP, and policy expression with communities and local preference.

Design Considerations #

  • Policy-first. Default to “deny” and explicitly allow intended imports and announcements. Keep filters close to neighbors and keep global defaults conservative.
  • Deterministic preference. Set localpref for inbound path selection inside the AS; use communities for structured policy signaling.
  • Scale boundaries. In small fabrics, a full-mesh iBGP suffices. For larger topologies, introduce route reflectors and keep reflector state minimal.
  • RPKI. Validate origins for received routes; drop roa invalid. Schedule rpki-client(8) to refresh ROAs.
  • Observability. Treat bgpctl show summary, show neighbor, and show rib {in,out} as part of every change and incident procedure.
  • Change control. Stage edits, syntax-check, and keep a roll-back path (console or timed revert) when touching upstream sessions.

Configuration #

1) Service lifecycle and skeleton #

Create a minimal skeleton with the local AS and router ID. Enable the daemon.

## /etc/bgpd.conf — minimal skeleton
AS 64512
router-id 198.51.100.2

# rcctl enable bgpd
  # Start on boot
# bgpd -n -f /etc/bgpd.conf
  # Syntax check (no start)
# rcctl start bgpd
  # Launch the daemon

2) Single-homed eBGP to an upstream (announce specific prefixes) #

Assumptions:

  • Public prefixes: 198.51.100.0/24, 2001:db8:100::/48
  • Upstream neighbor: 203.0.113.1, neighbor AS 64500
  • eBGP source address: 198.51.100.2
## /etc/bgpd.conf — eBGP to one ISP with explicit outbound and guarded inbound
AS 64512
router-id 198.51.100.2

# Prefixes intended for announcement
prefix-set "our-net" {
    198.51.100.0/24,
    2001:db8:100::/48
}

neighbor 203.0.113.1 {
    remote-as 64500
    descr "ISP-A"
    local-address 198.51.100.2
    enforce neighbor-as yes
    max-prefix 500000 restart        # Tune per provider guidance
    announce none                     # Outbound controlled by match rules below
}

# Inbound: accept from the upstream (subject to max-prefix and future filters)
allow from neighbor 203.0.113.1

# Outbound: announce only approved prefixes to this neighbor
match to neighbor 203.0.113.1 prefix-set "our-net" announce

Reload and verify:

# bgpctl reload
  # Graceful reconfiguration
$ bgpctl show summary
  # Session state, prefix counts, per-neighbor stats
$ bgpctl show neighbor 203.0.113.1
  # Capabilities and last error (if any)
$ bgpctl show rib out neighbor 203.0.113.1
  # Only approved prefixes should be advertised

3) Dual-homed eBGP (prefer one upstream with localpref; communities on egress) #

Assumptions:

  • Second upstream: 198.51.100.1, AS 64496
  • Preference: routes from ISP-A should win over ISP-B by higher localpref
  • Egress tagging: set a reference community on announced routes (example only)
## /etc/bgpd.conf — two providers; deterministic preference and egress tagging
AS 64512
router-id 198.51.100.2

prefix-set "our-net" { 198.51.100.0/24, 2001:db8:100::/48 }

neighbor 203.0.113.1 {
    remote-as 64500
    descr "ISP-A"
    local-address 198.51.100.2
    enforce neighbor-as yes
    max-prefix 500000 restart
    announce none
}

neighbor 198.51.100.1 {
    remote-as 64496
    descr "ISP-B"
    local-address 198.51.100.2
    enforce neighbor-as yes
    max-prefix 500000 restart
    announce none
}

# Inbound acceptance from both
allow from neighbor 203.0.113.1
allow from neighbor 198.51.100.1

# Prefer ISP-A inside the AS
match from neighbor 203.0.113.1 set localpref 200
match from neighbor 198.51.100.1 set localpref 150

# Outbound: announce the same set to both, with a reference community
match to neighbor 203.0.113.1 prefix-set "our-net" set community 64512:100 announce
match to neighbor 198.51.100.1 prefix-set "our-net" set community 64512:100 announce

Verification focus:

$ bgpctl show rib as 64500
  # Routes learned from ISP-A (AS path view)
$ bgpctl show rib | egrep '198\.51\.100\.0/24|2001:db8:100::/48'
  # Originated prefixes present in the RIB before export
$ bgpctl show neighbor | egrep 'LocalPref|Community'
  # Policy markers visible as expected

Announcements require that the route exist in the routing table (for example, via static routes or loopback assignments). Install deterministic originating routes (host /32 or /128 for service IPs, aggregates for blocks) before bgpd can export them.

4) iBGP within the AS (small fabric, full mesh) #

Assumptions:

  • Two routers, R1 (this host) and R2 at 10.0.0.2, both in AS 64512
  • Full-mesh iBGP; R1 preferred as exit to ISP-A via higher localpref applied to routes learned from that ISP
## /etc/bgpd.conf — add a simple iBGP peer
AS 64512
router-id 10.0.0.1

neighbor 10.0.0.2 {
    remote-as 64512
    descr "iBGP-R2"
    announce none
}

# iBGP acceptance
allow from neighbor 10.0.0.2

# Optional: restrict exchange to internal routes
prefix-set "internal" { 10.10.0.0/16, 10.20.0.0/16 }
match to neighbor 10.0.0.2 prefix-set "internal" announce

Verification focus:

$ bgpctl show summary
  # iBGP session should be Established
$ bgpctl show rib neighbor 10.0.0.2
  # Routes accepted from the peer
$ bgpctl show rib out neighbor 10.0.0.2
  # Routes advertised to the peer (filtered by "internal")

For larger topologies, introduce route reflectors to avoid a full mesh. Keep reflectors simple and limit re-advertisement to required address families and scopes.

5) RPKI origin validation (using rpki-client) #

Run rpki-client(8) periodically to fetch and validate ROAs, then have bgpd load the generated set. Reject roa invalid by policy.

# rcctl enable rpki_client
# rcctl start rpki_client
  # Starts periodic ROA fetch/validation; artifacts under /var/db/rpki-client/
# rpki-client -vv
  # On-demand run for initial population and diagnostics

bgpd configuration:

## /etc/bgpd.conf — load ROAs and drop invalids
AS 64512
router-id 198.51.100.2

roa-set {
    /var/db/rpki-client/openbgpd
}

# Policy: do not accept routes with invalid origin per ROA
deny from any roa invalid

# Allow remaining imports per neighbor rules

Observe RPKI state:

$ bgpctl show rib roa invalid
  # Routes rejected due to invalid origin
$ bgpctl show rib roa unknown | head
  # Routes without covering ROAs (informational)

6) Anycast service advertisement inside the AS #

For an internal anycast service (for example, resolver 10.10.255.53/32), originate the address on each serving node (lo0 alias or static route), and announce using iBGP. ECMP or policy then steers clients.

## /etc/bgpd.conf — originate a host route for anycast via iBGP
AS 64512
router-id 10.0.0.1

network 10.10.255.53/32
  # Route must exist in the RIB (lo0 alias or static) before export

Verification #

Core commands with bgpctl(8) :

$ bgpctl show summary
  # Session state and counters
$ bgpctl show neighbor <addr>
  # Capabilities, timers, last error
$ bgpctl show rib
  # Loc-RIB; append 'in' or 'out' with 'neighbor <addr>' for per-peer views
$ bgpctl show rib community 64512:100
  # Filter by community; useful for policy checks
$ bgpctl log verbose
  # Increase bgpd(8) log verbosity temporarily during troubleshooting

Wire-level and system checks:

# tcpdump -ni egress port 179
  # Observe BGP OPEN/KEEPALIVE/UPDATE on the wire
$ route -n show -inet ; route -n show -inet6
  # Originating/static routes present for announced prefixes

Troubleshooting #

  • Session stuck Idle/Active. Confirm IP reachability, local-address, and that PF allows TCP/179. Validate that remote-as matches the peer’s configured local AS and that enforce neighbor-as is not blocking expected paths.
  • No announcements leaving. The route must exist in the RIB (network statement or static route). Confirm that an explicit match ... announce rule targets the neighbor. Inspect bgpctl show rib out neighbor ....
  • Excessive routes from a peer. Raise or add max-prefix with restart and a warning threshold. Constrain scope with prefix-lists or prefix-set filters.
  • Inbound path not preferred. Review localpref on received routes. Check whether more-specifics or MEDs override intent.
  • RPKI drops unexpected routes. Inspect bgpctl show rib roa invalid and cross-check current ROAs on the parent ROA repository. Investigate ROA state before relaxing policy.
  • Flapping after reloads. Use bgpctl reload for graceful policy updates. For structural changes (peer add/remove), apply during maintenance windows or off-peak hours.

See Also #