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• CommentRowNumber1.
• CommentAuthorAndrew Stacey
• CommentTimeAug 14th 2017

Older nLabians may or may not recall that the original URL of the nForum was nforum.mathforge.org, and that at times it was useful to have a back-up hostname for the nlab itself which was nlab.mathforge.org. As I still rent the mathforge.org domain, I’ve kept these pointing at the nforum and nlab to avoid dead links.

I’m in the process of doing a bit of housekeeping at mathforge, and in so doing I’m updating the nforum.mathforge.org and nlab.mathforge.org DNS entries so that they are CNAME not A entries. (If that means nothing to you, you probably should have stopped reading a while ago.) This is what they should have been originally: cname is like a symbolic link and means that if ncatlab.org moves then these will follow it.

For the record, once DNS hosts are updated, then they will alias as follows:

• nforum.mathforge.org to nforum.ncatlab.org
• nlab.mathforge.org to ncatlab.org

If they should be otherwise, let me know.

I’m pleased to see that the nLab/nForum are still going strong!

• CommentRowNumber2.
• CommentAuthorTobyBartels
• CommentTimeSep 29th 2017
• (edited Sep 29th 2017)

Thanks for keeping these going! But right now I get a Cloudfare page complaining of a DNS resolution error for each of them.

• CommentRowNumber3.
• CommentAuthorTobyBartels
• CommentTimeSep 30th 2017
• CommentRowNumber4.
• CommentAuthorMike Shulman
• CommentTimeSep 30th 2017

I get the error page too.

• CommentRowNumber5.
• CommentAuthorAndrew Stacey
• CommentTimeOct 2nd 2017

So do I, however a little bit of digging gets me the following:

~% host nforum.mathforge.org
nforum.mathforge.org is an alias for nforum.ncatlab.org.
nforum.ncatlab.org has address 104.27.170.19
nforum.ncatlab.org has address 104.27.171.19
nforum.ncatlab.org has IPv6 address 2400:cb00:2048:1::681b:ab13
nforum.ncatlab.org has IPv6 address 2400:cb00:2048:1::681b:aa13
~% host nforum.ncatlab.org
nforum.ncatlab.org has address 104.27.171.19
nforum.ncatlab.org has address 104.27.170.19
nforum.ncatlab.org has IPv6 address 2400:cb00:2048:1::681b:aa13
nforum.ncatlab.org has IPv6 address 2400:cb00:2048:1::681b:ab13


So the alias is pointing to the right place. Doing whois 104.27.171.19, I get that it is registered to cloudfare.

So cloudfare is at your end, not mine. It may well be that the type of redirect I’ve set up doesn’t work with cloudfare’s system in which case I can set it back to the other type of redirect, but then I need to keep an eye on your IP address to ensure that it tracks it. Or it might be that the alternative hostnames need registering with cloudfare so that it knows to expect them.

1. You should be able to use a one line .htaccess file to redirect nforum.mathforge.org to nforum.ncatlab.org, without using IP addresses.

• CommentRowNumber7.
• CommentTimeOct 2nd 2017

Yeah, this is due to the way Cloudflare works. On the other hand, a 301 permanent redirect is probably the “correct” thing to do since the pages have, after all, “moved permanently”. If that’s not annoying for you to set up, Andrew, it would certainly be appreciated.

• CommentRowNumber8.
• CommentAuthorAndrew Stacey
• CommentTimeOct 2nd 2017

Yes, I can do a 301. That’s not a problem. I had hoped that a CNAME would work since then the requests get diverted at the DNS level and never reach my server. But I guess that the number of such requests is so small (being just a few links here and there) that it’s not an issue.

I’ll get that set up in the next few days.

• CommentRowNumber9.