Why cname is bad

Good, or Bad? Asked 7 years, 1 month ago. Active 7 years, 1 month ago. Viewed times. Your website www. Why is this "good"? Please note ' TTL'. Improve this question. Can you whittle this question down to be shorter? We don't need that much detail. I think I was spilling my heart out. It was late.

I've removed Introduction. Add a comment. Active Oldest Votes. A not uncommon setup is something like this: example. Improve this answer. Tim Fountain Tim Fountain 4, 1 1 gold badge 17 17 silver badges 19 19 bronze badges.

To create some perspective, a dig from our network to one of our sites, via our own dns: 79millisec. A dig on google. While at the same time later dropping all record types if at some point it finally looks up and caches a CNAME? Sounds like a race condition to me! In general resolvers look up one type and cache the result for that one type.

A CNAME is a special kind of answer that says "This name should be considered equivalent to this other name, go find out what that other name has" and as-such the CNAME is cacheable for queries of all types. I don't mean to point fingers, but in this case that's what happened; CloudFlare's behavior ignores the RFCs [1] and leads to nondeterministic results. Excellent explanation, thank you. The correct way todo this is setup a load balancer, then use route 53 to manage the dns, set the root domain to your load balancer I'D then map the www cname to the root domain, this solves all problems and takes under 5 minutes to configure.

If you want one to be "canonical", then the other should respond Moved Permanently with the correct address. Duplicate content across domains is a mess for SEO. I found them to be kinda expensive at moderate scale. But maybe I was doing something wrong. We should not be using A records for websites.

The article points to an AWS article on how to set up the whole thing correctly - but once you've done that, there's still another problem: You really shouldn't host public stuff with S3 at all, unless you use CloudFront in front of it. Try benchmarking it with Apache Bench: S3 is extremely slow, whereas CloudFront is fast and can take a large number of hits.

I came here to add this exact statement. I'll have to check that out. I'm a little confused by why this was even an issue. Why couldn't he just setup an A record for both domain. Is that not the best practice? Yes it is and has been for a long time. What this article really boils down to is a terribly poor understanding of how DNS works and why certain records are use for certain serivces. In the case of www. Would protocol specific SRV records be better? Yes, but since that change isn't happening quickly do what's right now and change in the future.

Because he's not self-hosting his website. He's using a S3 bucket, and the "normal" way of doing that is to CNAME to a S3-owned hostname, so Amazon can then mess with the IP address behind the scenes without telling you to update your A record. To the best of my knowledge one cannot use Route 53 and also take advantage of CloudFlare's services.

Yes, unfortunately I had to choose between the two. I like CloudFlare a lot but without that I was unable to stay. I'm surprised that so many of the comments in this thread are about dns hosting services and not dns server software support for these so-called "alias records". I was making a list of "why on Earth doesn't this simple software exist?

Does any common DNS server package provide this support easily out of the box? It seems like one of the most common uses cases possible. Server Fault is a question and answer site for system and network administrators.

It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. I've looked online and have not found a clear answer. Some people claim that CNAME records are bad they are not, however, clear on why this is and propose the following setup:. Note: The subdomains do not require their own MX records, so that is not an issue here. In the discussions I've been part of, the arguments tend to go like this:.

After trying a couple of different ways to do this, I now have a personal favorite style. It is:. I find that this setup works well. Sign up to join this community. The best answers are voted up and rise to the top.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Ask Question. Asked 11 years, 2 months ago. Active 8 years, 6 months ago. Viewed 82k times. I manage multiple websites that currently have the following DNS configuration: example.