Understanding route53 Alias records

Good documentation + Handson = ❤

What is route53 ?

AWS route53

It is Domain Name System( DNS) provider by AWS. More info from AWS official link.

DNS record types

There are more than 20 type of dns records below are few which are heavily used

A => IPV4 address(s) 
CNAME => Canonical Address or simply, address pointing to other CNAME(s) or A record(s) 
MX => Mail Exchange Server 
AAAA => IPV6 address ...

route53 supports following DNS record types

route 53 record types

Now you may wonder how we can use multiple record(s) ?

www.playground.com A     192.168.2.22 
                         192.168.2.23
app.playground.com CNAME www.playground.com 
                         playground.com

We can use multiple records and querying the DNS will result in any one of the entry randomly being picked(order is random) this can act as cheap load balancer, though not ideal in critical application because if server listening on 192.168.2.23 is down/ unhealthy, DNS will still can randomly resolve that ip.

AWS Non Alias Records

• They are simply DNS records (A,CNAME,MX, .. ) that we do for any DNS servers
• below I have added one A record and 2 CNAME records

Lets verify the DNS entry by issuing dig unix command, here’s wiki on dig

1. A record

2. CNAME record

AWS Alias Records

Note: we are using AWS nameservers, though we can also use Google’s DNS 8.8.8.8

ns-517.awsdns-00.net. 
ns-1505.awsdns-60.org.
ns-1910.awsdns-46.co.uk. 
Ns-441.awsdns-55.com.

Alias records in AWS are records which points to some AWS recources like

This is full list of entries we can have for Alias records

Below I have added Alias A record to load balancer

which end up looking

If we dig www.playground.com we will endup resolving IP of the loadbalancer, lets verify

one of thing I didn’t discussed was health checks that Route53 DNS provides, which basically means if the evaluated IP is not healthy (depends if health check is set) Route53 DNS server won’t resolve to that IP….. anyways topic for some other day

Thats all for today, This is AWS guide to choosing Alias/Non Alias records

Originally published at https://itsjwala.github.io.