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# Graceful Restart
This page explains how to configure [Graceful Restart](https://tools.ietf.org/html/rfc4724).
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.
## Contents
- [Helper speaker](#helper)
- [Restarting speaker](#restarting)
## <a name="helper"> Helper speaker
Below is the configuration to enable helper speaker behavior.
```toml
[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.
```shell
$ 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 Refesh: 0 0
Discarded: 0 0
Total: 5 4
Route statistics:
Advertised: 1
Received: 0
Accepted: 0
```
## <a name="restarting"> Restarting speaker
To support restarting speaker behavior, try the configuration below.
```toml
[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.
```shell
$ gobgpd -f gobgpd.conf -r
```
Let's see how capability negotiation changes.
```shell
$ 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 Refesh: 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`.
|
