bird.conf

log syslog all;

router id $NODE_IP;

# Device is a special protocol that has no channels.
# it is to configure BIRD to scan network devices in OS.
# One Device protocol instance should be included in bird.conf
protocol device {
interface "$INTERFACE";
}

# also a special protocol that has no channels.
# It is always used alongside with other routing protocols 
# such as BGP to detect link failures very fast.
protocol bfd {
    interface "*" {
        interval 50 ms;
    };
}

# Direct is to import routes automatically generated by the kernel.
#protocol direct {
#  ipv4;
#}

# Kernel protocol is to exchange routes between a BIRD routing table and a kernel routing table (FIB).
protocol kernel {
  ipv4 {
         export filter {
         if proto = "direct" then reject;
         accept;
       };
  };
}

# "static" protocol is used to define routes that are manually configured
# instead of being learned dynamically through a routing protocol.
# it should be blackholed (dropped) instead of being forwarded.
protocol static {
  ipv4;
  route ${TO_BRIDGE_SUBNET} via ${TO_NODE_IP};
}


# configures an BGP instance that exchanges IPv4 routes between an iBGP peer
# running at $TO_NODE_IP 
# It imports all IPv4 routes from the peer router and exports all routes in master4 (default bgp routing table)
protocol bgp $HOSTNAME {
  local $NODE_IP as 65000;
  neighbor $TO_NODE_IP as 65000;

  ipv4 {
    import all;
    export all;
  };
}