[dns-operations] DNS load-balancing/failover using an ASR 9xxx (few questions)

[Warren Kumari]

On Thu, Aug 14, 2014 at 6:00 PM, Nat Morris <nat at nuqe.net> wrote:
> On 14 August 2014 18:48, Jake Zack <jake.zack at cira.ca> wrote:
>> In the ASR 9xxx series with IOS XR, the “ipsla” that it has available
>> doesn’t seem to do either TCP connections or UDP DNS queries.  It seems my
>> only real option is to monitor for ICMP reachability and nothing else.
>>
>> Anyone have a better solution?  I’ve considered throwing a wrapper around
>> BIND doing OSPF updates and such…but it seems unideal.

What seems unideal about it? It is a well know and understood
technique, relies only on open and tested core features. I'd suggest
doing BGP instead of OSPF, but much of that is personal preference...

>
> BGP sessions between the ASR 9xxxx and each DNS server in the cluster,
> ExaBGP running on them announcing their loopback/service /32 + /128
> address(es).

Yup, this also only uses well know, well understood systems - with
anything like the Cisco solution you end up with vendor lock-in - and
are subject to their whims (like what Jake described). ipsla is not
part of their core features and so changes over releases / platforms.
I'm sure they'd be happy to sell you an ACE though :-)

>
> Health check scripts on each service to probe for service ability,
> retract the announcement upon failure.
>
> --
> Nat
>
> https://nat.ms
> +44 7531 750292
>
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idea in the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair
of pants.
   ---maf