Quick and dirty jumpstart to peer Cilium with OpenBSD using the built-in OpenBGPD routing daemon.

cilium-bgp-peering-policy.yaml

apiVersion: "cilium.io/v2alpha1"                       
kind: CiliumBGPPeeringPolicy                           
metadata:                                              
 name: cilium-bgp-peering-policy                       
spec:                                                  
 nodeSelector:                                         
   matchLabels:                                        
     bgp: active                                       
 virtualRouters:                                       
 - localASN: 65432                                     
   exportPodCIDR: true                                 
   neighbors:                                          
    - peerAddress: '192.168.42.1/32'                     
      peerASN: 65432                                   
   serviceSelector:                                    
     matchExpressions:                                 
     - {key: gateway, operator: In, values: ['active']}

openbgpd.sh

#---------------------------------------------------------------------------------------------------------
# Quick and dirty jumpstart to Peer Cilium with OpenBSD using the built-in OpenBGPD routing daemon.
# Note: this is for demonstration purposes only and does not cover vital infomration such as protecting
# your network with the built in packet filter PF. Advance at your own risk.
#
# Start by installing OpenBSD 7.5 and then follow the shell script below:
#---------------------------------------------------------------------------------------------------------

#!/bin/sh

# Enable IP Forwarding
echo 'net.inet.ip.forwarding=1' >> /etc/sysctl.conf
sysctl net.inet.ip.forwarding=1

# Enable BGP Daemon
rcctl enable bgpd

# Create BGP Daemon configuration file
cat << EOF > /etc/bgpd.conf
# define our own ASN as a macro
ASN="65432"
# global configuration
AS $ASN
router-id 192.168.42.1
# list of networks that may be originated by our ASN
prefix-set mynetworks {
        10.0.0.0/8
        172.16.20.0/24
}
include "/var/db/rpki-client/openbgpd"
# assume simple network with 3 routers in IBGP full mesh
group "ibgp mesh" {
        remote-as $ASN
        # use loopback for IBGP sessions, assume it's distributed in OSPF
        local-address 192.168.42.1
        neighbor 192.168.42.101         # Cilium Peer # 1
        neighbor 192.168.42.102         # Cilium Peer # 2
}
## rules section
# IBGP: allow all updates to and from our IBGP neighbors
allow from ibgp
allow to ibgp
EOF

# Start BGP Daemon
rcctl start bgpd

#---------------------------------------------------------------------------------------------------------
# Once BGP is running you can connect your Cilium Peers
# A file such as the above `cilium-bgp-peering-policy.yaml` should be sufficient.
#---------------------------------------------------------------------------------------------------------

#---------------------------------------------------------------------------------------------------------
# Once you have peered Cilium and OpenBGPD you can view BGP routes from the OpenBSD command line:
#---------------------------------------------------------------------------------------------------------
# bgpctl show fib bgp
#   flags: B = BGP, C = Connected, S = Static
#          N = BGP Nexthop reachable via this route
#          r = reject route, b = blackhole route

#   flags prio destination                      gateway
#   B       48 10.0.1.0/24                      192.168.42.101
#   B       48 10.0.2.0/24                      192.168.42.102
#   B       48 172.16.20.1/32                   192.168.42.101

# That's all folks!