Proper use of graceful restart functionality

[Maria Matejka]

Hello!

The -R option basically prohibits local forwarding table cleanup before 
the BGP settles. It tries to not break your local routing by simply 
starting BIRD.

Maria

On 2023-10-16 18:44, Pavlos Parissis wrote:
> Hi all,
>
> I am using latest 2.x version of Bird and I have a question about  graceful restart.
>
> I have  `graceful restart on` for BGP protocol and I currently perform below steps when I want to utilize it:
> 1. birdc graceful restart
> 2. systemctl start bird.service
>
> According to the documentation I need `-R` command-line option, thus I have adjusted systemd unit file accordingly:
> ```
> ExecStart=/usr/sbin/bird -R -f -u bird -g bird
> ```
>
> How does the aforementioned command-line option behave when `birdc graceful restart` is not issued?
> I scanned the code to understand it and I think bird is smart enough to know that a graceful restarted was
> not requested and it doesn't do anything during the startup.
>
> While I was testing graceful restart functionality, I noticed that even without the aforementioned command-line
> option the upstream peer does not remove the routes until restart timeout expires. So, I was wondering if that
> option is real needed thus the question.
>
>
> Regards,
> Pavlos
>
>
-- 
Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
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