UPDATE: 13 Aug 2014 – Amazon Route 53 now does native GeoDNS within the product – see Amazon Route 53 GeoDNS Routing Policy
A new feature to Exchange 2013 is supported use of a single namespace for your global email infrastructure. For example mail.contoso.com rather than different ones for each region such as uk-mail.contoso.com; usa-mail.contoso.com and apac-mail.contoso.com.
GeoDNS means that you are given the IP address of a server that is in or close to the region that you are in. For example if you work in London and your mailbox is also in London then most of the time you will want to be connected to the London CAS servers as that gives you the best network response. So in Exchange 2010 you would use your local URL of uk-mail.contoso.com and if you used the others you would be told to use uk-mail.contoso.com. For GeoDNS support you use mail.contoso.com and as you are in the UK you get the IP address of the CAS array in London. When you travel to the US (occasionally) you would get the US CAS array IP address, but this CAS array is able to proxy your OWA, RPC/HTTP etc traffic to the UK mailbox servers.
The same is true for email delivery via SMTP. Email that comes from UK sourced IP addresses is on balance a statistical likelihood that it is going to the UK mailbox. So when you look up the MX record for contoso.com from a UK company you get the UK CAS array and the email gets delivered to the CAS array that is in the same site as the target mailbox. If the email is for a user in a different region and it hits the UK CAS array then it is proxied to the other region seamlessly.
GeoDNS is a feature provided by some high-scale DNS providers, but not something Amazon Web Services (AWS) Route 53 provides – so how do I configure GeoDNS with Amazon Web Services (AWS) Route 53 DNS Service?
Quite easily is the answer. Route 53 does not offer GeoDNS but does offer DNS that directs you towards the closest AWS datacentre. If your datacentres are in regions similar to AWS then the DNS redirection that AWS offers is probably accurate.
To set it up, open your Route 53 DNS console, or move your DNS to AWS (it costs $0.50/month for a zone at time of writing, AWS Route 53 pricing here) and then create your global Exchange 2013 namespace record in DNS:
- Click Create Record Set and enter the name. In the below example I’m using geo.c7solutions.com as I don’t actually have a globally distributed email infrastructure!
- Select A – IPv4 or if you are doing IPv6 select AAAA.
- Set Alias to No and enter the IP address of one of your datacentres
- Select the AWS region that is closest to this Exchange server(s) and enter a unique description for the Set ID value.
- The entry will look something like this:
- Save the Record Set and create additional entries for other regions. For the purposes of this blog I have created geo.c7solutions.com in four regions with the following IP addresses:
Region IP Address Region us-east-1 184.108.40.206 Northern Virginia us-west-1 220.127.116.11 Northern California eu-west-1 18.104.22.168 Ireland ap-northwest-1 22.214.171.124 Singapore sa-east-1 126.96.36.199 Sao Paulo ap-southeast-1 188.8.131.52 Sydney
- The configuration in AWS for the remaining entries looks like the following:
- And also, once created, it appears like this:
In addition to this blog, I’ve left the record described above on my c7solutions.com DNS zone. So depending upon your location in the world, if you open a command prompt and ping geo.c7solutions.com you should get back the IP address for the AWS region closest to you, and so get back an IP that represents a Exchange resource in your global region. Of course the IP’s I have used are not mine to use and probably will not respond to ping requests – but all you need to do is see it DNS returns the IP above that best matches the region that you are in.
I wrote this blog when in a hotel in Orlando and as you can see from the image below, it returns 184.108.40.206 which is the IP address associated with us-east-1.
But when I connected to a server in the UK and did the same ping geo.c7solutions.com I got the following, which show GeoDNS working when equating GeoDNS to AWS Latency DNS.
What do you get for your regions? Add comments and let us where you are (approximately) and what region you got. If enough people respond from enough places we can see if AWS can go GeoDNS without massive cost.
[Updated 13 Nov 2012] Added Sydney (ap-southeast-1) and fake IP address of 220.127.116.11
[Updated 27 April 2013] Added Northern California (us-west-1) and fake IP of 18.104.22.168