DNS anycast node monitor

[Frank Even]

On Thu, Apr 9, 2015 at 1:33 PM, Anand Buddhdev <anandb at ripe.net> wrote:
> On 09/04/15 16:50, Hillary Nelson wrote:
>
> Hi Hillary,
>
>> Currently we have about 20 DNS servers sit behind two pairs of F5 LTM on
>> campus, the two pairs of F5s using router injection for DNS virtual
>> addresses. This setup is costly and we are trying to use direct anycast
>> between router and server instead, with quagga and bgp.
>
> If you merely want to announce a route from the DNS server to the
> router, and don't need to receive routes and insert them into the
> server's routing table, then consider ExaBGP. It's great for simply
> announcing prefixes via BGP.
>
> We use this setup at the RIPE NCC and it works rather well.
>
>> The decision of advertise/withdraw route seems to be most critical one. I
>> guess we'll need two monitors, one on the server, another like nagios
>> monitor from a remote system.  I know there are people doing this for many
>> year, wonder if
>> there are working script that would like to share.
>
> We run ExaBGP under the CentOS 6 upstart supervisor. ExaBGP's upstart
> script is configured to stop it on certain events. We use another
> upstart script to monitor the DNS server (with queries using dig), and
> if the DNS server doesn't respond, then an event is emitted causing
> exabgp to die, and withdraw the route to that server. The client almost
> doesn't notice this.
>
> You can also run all this under systemd if you wish, with its
> dependencies. Or use monit, which can also let you define dependencies,
> and stop or start services under certain condition. I don't have all the
> URLs handy, but I'm sure you can search for all these things.
>

Quagga works fine as well.