NOTE: This feature does not work on Windows at present since the gobgp project does not support windows.
This feature integrates the functionality of gobgpd with fabio. This is particularly useful in the scenario where we are using anycast IP addresses and want to dynamically advertise to upstream routers when we’re ready to receive traffic. In the past, we’ve used external router packages such as quagga or frr to handle this for us, but it’s potentially messy to make sure that the route advertisement stops if fabio goes down, and the bgp daemon is started back up once fabio is running again. By integrating the bgp advertisement with the proxy server, we’ve made sure that when fabio goes down, the route is no longer advertised and traffic can be sent to other fabio instances accordingly. When fabio is back up, the route is advertised again.
Multihop is supported, where fabio may not be on the same subnet as neighbor.
To enable BGP, you must at a minimum:
- Set up an anycast interface on the host with a /32 address. On linux, the dummy interface type is a good option since it’s supported using network manager. Another option is hanging this address off of loopback.
- Configure the neighbor / peer / upstream router to allow us to peer, and to allow our anycast as a prefix it will accept
- Set bgp.enabled=true
- Configure the bgp.asn to be our router’s Asn - probably use a private ASN here
- Configure the bgp.routerid to be our router’s IP address (i.e., not the anycast address, something unique). This will be the default nexthop of all routes we publish.
- Configure the bgp.peers for at least one nieghbor.
- Configure the bgp.anycastaddresses for at least one anycast address.
This will embed a gobgpd instance inside of fabio on startup and it will publish the configure anycast addresses.
It will also configure a gobgpd policy that will reject all incoming prefixes from neighbors.
Alternatively, for more advanced use cases, you can reference an external gobgpd config file that will override many of the options set in the fabio config, including the policy blocking us from accepting prefixes from neighbors. You still need to specify the bgp.grpc options from the fabio config since there is no analog in the gobgpd config file. You may still specify bgp anycastaddresses or bgp.peers from the fabio config, but we ignore anything that would be specified in the global section of the gobgpd config file, including router ID and the ASN. Even If the bgp.gobgpdcfgfile value is set, fabio will still honor any values configured for bgp.anycastaddresses or bgp.peers. These will be processed after the config file is processed.
For situations where multiple fabio instances are running with the same anycast address in the same datacenter, or in any other situation where the path distance is the same and load balancing across multiple fabio instances is desired, the details of ECMP configuration is outside the scope of this document as configuration would vary greatly depending on the details of the upstream router.