Graceful Restart

This page explains how to configure Graceful Restart, Graceful Restart Notification Support and Long Lived Graceful Restart. Graceful Restart has two sides. One is restarting speaker which does restart, the other is receiving speaker (helper speaker) which helps a restarting speaker to do graceful restart. GoBGP supports both roles.

Helper speaker

Below is the configuration to enable helper speaker behavior.

[global.config]
  as = 64512
  router-id = "192.168.255.1"

[[neighbors]]
  [neighbors.config]
    neighbor-address = "10.0.255.1"
    peer-as = 65001
  [neighbors.graceful-restart.config]
    enabled = true

Check graceful restart capability is negotiated.

$ gobgp n 10.0.255.1
BGP neighbor is 10.0.255.1, remote AS 65001
  BGP version 4, remote router ID 192.168.0.2
  BGP state = BGP_FSM_ESTABLISHED, up for 00:00:36
  BGP OutQ = 0, Flops = 0
  Hold time is 0, keepalive interval is 30 seconds
  Configured hold time is 90, keepalive interval is 30 seconds
  Neighbor capabilities:
    BGP_CAP_MULTIPROTOCOL:
        RF_IPv4_UC:     advertised and received
    BGP_CAP_ROUTE_REFRESH:      advertised and received
    BGP_CAP_GRACEFUL_RESTART:   advertised and received
        Remote: restart time 90 sec
            RF_IPv4_UC
    BGP_CAP_FOUR_OCTET_AS_NUMBER:       advertised and received
  Message statistics:
                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                2          1
    Keepalives:             2          2
    Route Refresh:          0          0
    Discarded:              0          0
    Total:                  5          4
  Route statistics:
    Advertised:             1
    Received:               0
    Accepted:               0

Restarting speaker

To support restarting speaker behavior, try the configuration below.

[global.config]
  as = 64512
  router-id = "192.168.255.1"

[[neighbors]]
  [neighbors.config]
    neighbor-address = "10.0.255.1"
    peer-as = 65001
  [neighbors.graceful-restart.config]
    enabled = true
    restart-time = 120
  [[neighbors.afi-safis]]
    [neighbors.afi-safis.config]
    afi-safi-name = "ipv4-unicast"
    [neighbors.afi-safis.mp-graceful-restart.config]
        enabled = true

By this configuration, if graceful restart capability is negotiated with the peer, the peer starts graceful restart helper procedure, when gobgpd dies involuntarily or SIGINT, SIGKILL signal is sent to gobgpd. Note when SIGTERM signal is sent to gobgpd, graceful restart negotiated peers don't start graceful restart helper procedure, since gobgpd sends notification messages to these peers before it die.

When you restart gobgpd, add -r option to let peers know gobgpd is recovered from graceful restart.

$ gobgpd -f gobgpd.conf -r

Let's see how capability negotiation changes.

$ gobgp n 10.0.255.1
BGP neighbor is 10.0.255.1, remote AS 65001
  BGP version 4, remote router ID 192.168.0.2
  BGP state = BGP_FSM_ESTABLISHED, up for 00:00:03
  BGP OutQ = 0, Flops = 0
  Hold time is 0, keepalive interval is 30 seconds
  Configured hold time is 90, keepalive interval is 30 seconds
  Neighbor capabilities:
    BGP_CAP_MULTIPROTOCOL:
        RF_IPv4_UC:     advertised and received
    BGP_CAP_ROUTE_REFRESH:      advertised and received
    BGP_CAP_GRACEFUL_RESTART:   advertised and received
        Local: restart time 90 sec, restart flag set
            RF_IPv4_UC, forward flag set
        Remote: restart time 90 sec
            RF_IPv4_UC
    BGP_CAP_FOUR_OCTET_AS_NUMBER:       advertised and received
  Message statistics:
                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                2          1
    Keepalives:             1          1
    Route Refresh:          0          0
    Discarded:              0          0
    Total:                  4          3
  Route statistics:
    Advertised:             1
    Received:               0
    Accepted:               0

You can see restart flag and forward flag is set.

Without -r option, the peers which are under helper procedure will immediately withdraw all routes which were advertised from gobgpd.

Also, when gobgpd doesn't recovered within restart-time, the peers will withdraw all routes. Default value of restart-time is equal to hold-time.