Forum Discussion
devious_381979
Nimbostratus
NimbostratusGTM and SRV Records
Hello
We have been asked by our customer to provide DNS resolution based on geography, e.g. US clients get given a US server IP, European clients a European server IP etc. Topology records are clearly a good fit here in terms of technology. There is one thing, however, which I'm a little stumped by, simply because I've never worked with them. They are SRV records.
From what I've have read about SRV records & what I know about the GTM it looks like we cannot use Topology records in the same way as standard A records.
I know this question might at first sound a little vague but would appreciate a steer on this one from the community. What things I need to consider? Can this even work? Any other questions to ask them to try get to a resolution everyone can be happy with.
Thank you.
- Kai_Wilke
MVP
Hi Devious,
a SRV records is basically an extended CNAME record with additonal a Weigth/Priority/Port values for the resolved HOST-Name(s).
when DNS_REQUEST { Searching for DNS request for SRV = _sip._tcp.domain.de if { ( [string tolower [DNS::question name]] equals "_sip._tcp.domain.de" ) and ( [DNS::question type] equals "SRV" ) } then { Defining DNS answer for the requested SRV record (Question Name = _sip._tcp.domain.de., ttl = 600, class = IN, type = SRV, priority = 100, weight = 100, port = 5060, hostname = sip.domain.de ) DNS::answer insert "_sip._tcp.domain.de. 600 IN SRV 10 100 5060 sip1.domain.de" DNS::answer insert "_sip._tcp.domain.de. 600 IN SRV 20 100 5060 sip2.domain.de" Changing "Authorative Answer" DNS header to true. DNS::header aa 1 Sending the DNS response DNS::return } } }After your DNS client gets the SRV response, it will perform an additional A or AAAA query for the just received HOST names. The subsequent A or AAAA request may then target a wide-IP as usuall...
Note: The SRV response may already include the A or AAAA DNS responses for the just resolved HOST names to speed up DNS resolution. To make those additional A or AAAA DNS answers GLBS aware you would need a handcrafted logic to perform the country checks and flip the IP based on those information. Its not rocket science, but still far more complicated than using two independent DNS queries/responses...:-)
Cheers, Kai
devious_381979Don’t mean to bump this up but also wondered - is it possible an SRV record could have a target/resource that is itself a Wide IP and therefore we could utilise Topology load balancing?
For example:
_sip._tcp.wideipname
