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This morning, Network Solutions (where we host our DNS) had some intermittent DNS Server outages. All of our sites were inaccessible during this time. When network solutions DNS Servers came back up, so did our sites.

Our DNS TTLs are currently set to 300. If we increase the TTLs to 86400, will that effectively prevent outages caused by intermittent DNS Server outages?

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Unfortunately this will only help for those visitors who use a resolver that has looked the site up within the last 86400 seconds. Every new visitor to the site will do a DNS lookup to find the site. If their resolver has a record that is still cached (i.e. does not exceed the TTL of 86400 second, and has not been cleared from the resolver cache for some other reason), then the resolver won't try to get a new record from your DNS, and so it will work for that visitor. But if the resolver hasn't yet had reason to look your site up, or it's cleared its cache for some reason, then the resolver will have to ask your DNS for the record and it will fail.

This is why it is a good practice to have two separate DNS servers on different networks.

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Makes total sense. Thanks. –  Adam Balsam Jul 17 '13 at 19:08
    
You're welcome! (And unfortunately I have no answer to the obvious follow-up question, which is "how much can Network Solutions suck before going out of business"...) –  Jenny D Jul 17 '13 at 19:49

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