best practices for two-location DDNS for a single domain

[Chris McCraw]

Hi there,

Due to a variety of semi-political issues in our environment, we're
looking for a way to implement the following:

- 2 locations with standalone-capable local nameservers which serve
the same domain (ie, in case of network failure between them, we want
them both to go on working as authoritative for the domain for local
clients.)
- using dynamic dns (client updates) in two locations for that same
domain.  Updates from either master need to be visible to clients of
each master, though a slight lag in syncing would be acceptable.
- fortunately this is entirely for internal DNS and need not present a
coherent picture to non-local clients.

Normally, I'd want to split it into one subdomain per location and
have authoritative servers for each which just referred to the other
for the other's zone, or use a master/slave setup and
allow-update-forwarding, but that leaves the slave location unusable
(or at least underperforming) in case of network failure, as I
understand it.

But those aren't an option here - they both need to serve the same
domain and both need to allow local DDNS updates visible from both
sides, and work in the absence of a network between the two.  I've
done some searching and it does not appear that BIND fully supports
this setup natively.  Please correct me if I'm wrong!

I found a potential workaround using a dual-master setup with some
magic to manually sync the updates back and forth, but that magic
seems like it might end up being fragile.

Any other suggestions about how to accomplish this?

Thanks in advance for your help!

-- 
Chris McCraw | New Relic - http://blog.newrelic.com - NewRelic at Twitter