How can old versions of websites be appearing on the web?

Question

All websites in the freeserve.co.uk and fsnet.co.uk domains (e.g. www.divdev.fsnet.co.uk/scicaf.htm which has an update date on the page) sometimes show their latest version but sometimes show their March 2014 version (but never an intermediate version). If one accesses these sites in two windows via two routes (eg with and without the www, or via a proxy server) one sometimes sees both versions of the site at the same time. This has been going on for weeks and happens on all networks and devices and all geographic locations - UK, Germany, South Africa and USA anyway.

When website owners upload to their websites, the upload goes to IP 195.92.193.56. However, internet accesses to freeserve websites sometimes go to 195.92.193.56 but sometimes go to 195.92.193.55, and I think 195.92.193.55 must contain out-of-date March 2014 versions.

I am not an expert (hence this post) but it seems to me the problem is either a DNS routing issue, i.e. one of EE's DNSs is wrongly routing website visitors to 195.92.193.55 (intoDNS shows an SOA Serial error for the freeserve.co.uk domain but I do not know how significant that is), OR (if it's EE's intention that freeserve.co.uk websites are supposed to be duplicated at these 2 IP addresses) the problem is that updates to 195.92.193.56 are not being copied across to 195.92.193.55 – and have not been since March 2014.

Is the above plausible? Could there be another cause?

Answer 1

They have four name servers and different name servers are responding differently to DNS queries.

$ dig fsnet.co.uk NS
;; ANSWER SECTION:
fsnet.co.uk.        28800   IN  NS  pridns2.svr.pol.co.uk.
fsnet.co.uk.        28800   IN  NS  pridns3.svr.pol.co.uk.
fsnet.co.uk.        28800   IN  NS  pridns1.svr.pol.co.uk.
fsnet.co.uk.        28800   IN  NS  pridns4.svr.pol.co.uk.

$ dig @pridns1.svr.pol.co.uk www.divdev.fsnet.co.uk
;; ANSWER SECTION:
www.divdev.fsnet.co.uk. 3600    IN  A   195.92.193.55

$ dig @pridns2.svr.pol.co.uk www.divdev.fsnet.co.uk
;; ANSWER SECTION:
www.divdev.fsnet.co.uk. 3600    IN  A   195.92.193.56

$ dig @pridns3.svr.pol.co.uk www.divdev.fsnet.co.uk
;; ANSWER SECTION:
www.divdev.fsnet.co.uk. 3600    IN  A   195.92.193.55

$ dig @pridns4.svr.pol.co.uk www.divdev.fsnet.co.uk
;; ANSWER SECTION:
www.divdev.fsnet.co.uk. 3600    IN  A   195.92.193.56

If the content on 195.92.193.55 is out of date, about half the users will get that depending on which DNS server their requests use.