The virtual router is implented using the keepalived(8) package from the Keepalive project. Keepalived can do a lot of thingd but I only use the VRRP (Virtual Redundant Router Protocal) part of the package.

Nounours is the chosen master router since it has the best connection to the Internet. Gate-rpi is then the backup router. Configuration is done following the guidelines on the ArchLinux Wiki.

Here are the configurations files. On both routers they may be found at /etc/keepalive/keepelive.conf.

global_defs {
 notification_email {
   bent@oz6bl.dk
 }
 notification_email_from keepalived@nounours.oz6bl.dk
 smtp_server localhost
 smtp_connect_timeout 30
 router_id ROUTER1
}
vrrp_instance NET19 {
  state MASTER
  interface br0
  virtual_router_id 19
  priority 10
  advert_int 1
  authentication {
      auth_type PASS
      auth_pass verysec
  }
  virtual_ipaddress {
      192.168.19.254
  }
}

global_defs {
 notification_email {
   bent@oz6bl.dk
 }
 notification_email_from keepalived@gate-rpi.oz6bl.dk
 smtp_server localhost
 smtp_connect_timeout 30
 router_id ROUTER44
}
vrrp_instance NET19 {
  state BACKUP
  interface eth0
  virtual_router_id 19
  priority 5
  advert_int 1
  authentication {
      auth_type PASS
      auth_pass verysec
  }
  virtual_ipaddress {
      192.168.19.254
  }
}