Virtual IP with ExaBGP

exabgp-setup.sh

#!/usr/bin/env bash

LOCAL_AS=65210
PEER_AS=65200
LB_IP="1.2.3.4"

HOST_IP=`ip address list | grep "scope global" | grep -v "scope global lo" | cut -d" " -f6 | cut -d"/" -f 1`
GATEWAY=`ip route | grep "^default" | cut -d" " -f3`
EXA_BGP_CONFIG="/etc/exabgp/exabgp.conf"
EXA_BGP_CHECK="/etc/exabgp/exabgp-check.sh"

if [ "$1" == "turndown" ]; then
    ip addr del ${LB_IP}/32 dev lo
    exit 0
fi

if ip address  list lo |grep ${LB_IP}
then
    echo "${LB_IP}/32 is already set"
else
    ip add a ${LB_IP}/32 dev lo
fi

cat <<EOF > ${EXA_BGP_CONFIG}

group LB {
    hold-time 180;
    local-as ${LOCAL_AS};
    peer-as ${PEER_AS};
    # local physical interface address
    router-id ${HOST_IP};

    # neighbor is default gateway address
    neighbor ${GATEWAY} {
        # local-address = local physical interface address
        local-address ${HOST_IP};
        description "LB to router";
        process exabgp-check {
                run /etc/exabgp/exabgp-check.sh;
        }

    }

}
EOF

cat <<EOF > ${EXA_BGP_CHECK}
#!/usr/bin/env bash

STATE="down"

VIP="${LB_IP}"
GW_IP="${HOST_IP}"

while true; do
  ip address list lo |grep ${VIP}/32 >/dev/null 2>&1

  if [[ \$? == 0 ]]; then
    if [[ "\$STATE" != "up" ]]; then
      echo "announce route \${VIP}/32 next-hop \${GW_IP}"
      STATE="up"
    fi
  else
    if [[ "\$STATE" != "down" ]]; then
      echo "withdraw route \${VIP}/32 next-hop \${GW_IP}"
      STATE="down"
    fi
  fi

  sleep 1
done

EOF

chmod 755 ${EXA_BGP_CHECK}