From: istong@stong.org
Date: Tue Nov 29 2005 - 15:33:44 GMT-3
Leigh,
A "normal" time for a DNS change to propogate would be
roughtly 24 hours. Depends a lot on how various systems are
configured. Some systems may be setup to cache entries for
longer than that. Typically you make a change and 24 hours
later it's propagated. You can set your NS to a much lower
TTL such as 5 minutes if you want your entries to time out
faster. Often done if you are doing global DNS or making
lots of changes to your records.
Hope that helps,
Ian
www.ccie4u.com
> Brian,
>
> Any comments are welcomed!!
>
> I've been asked to look into the changing of the dns ttl
> to aid in disaster recovery (from one ip to another).
>
> I was under the impression that it takes around 24 hrs for
> a dns change to propogate around the internet. So from
> that I guess that the dns change over time is purely
> academic. 5-6 mins is not a great problem when it's
> going to take hours for it to properly settle.
>
> I guess what I am really asking is how long does it really
> take for the dns change to propogate around the internet?
>
> I'm also going to suggest a redesign of the data centre,
> incorporating 2 bgp feeds, and content switching, etc.
>
> How long would it take for a change in dns to propogate
> around the internet - although to be fair, I'm mainly
> interested in the timing for a site in the UK, dns
> changed in the UK. How long before the change would be
> seen in Europe ?
>
> LH
>
>
> blodwick wrote:
>
> >After looking back over your email again Leigh I went off
> on a tangent >about something else probably not related.
> Sorry about that. I'm a goof >:)
> >
> >~ Brian L
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of >blodwick
> >Sent: Tuesday, November 29, 2005 8:51 AM
> >To: 'Ian Stong'; 'Leigh Harrison'; 'FORUM'
> >Subject: RE: DNS Disaster Recovery Question
> >
> >I believe what Leigh is talking about is an intelligent
> DNS device that >communicates state information either
> directly with the server or with a >local content device
> before sending resolution. The Cisco device is >called a
> Global Site Selector (GSS). If you were to use DNS round
> robin >you would obviously be sent to a non-working server
> 50% of the time >during an outage (if you had 2 data
> center options). There are further >advantages if you use
> the Cisco Content Services Switch (CSS) locally at >each
> data center and use the GSS to control disaster recovery.
> The CSS >locally at each data center can load-balance the
> local servers and will >communicate to the GSS local state
> information. With the CSS locally you >can also utilize
> scripted keepalives to take establishing server "state"
> >to the next level. This subject gets quite involved, but
> imagine being >able to query a java applet on your web
> server that would in turn query >your back end database.
> You would be able to assure that users were >always being
> sent to a web server that has an operational web engine,
> >know java is operating properly and that your backend
> database is >reachable and responding properly to queries.
> >
> >~ Brian L
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of >Ian Stong
> >Sent: Tuesday, November 29, 2005 8:10 AM
> >To: 'Leigh Harrison'; 'FORUM'
> >Subject: RE: DNS Disaster Recovery Question
> >
> >Haven't worked with them myself. Curious what else they
> provide since >just
> >setting the TTL to 5 mins can be done by anyone. It's
> just a setting >you
> >use on the NS entries of your DNS server. You could even
> use a free DNS >hosting service such as zoneedit.com and
> set your TTL to 5 mins. >
> >
> >Ian
> >http://www.ccie4u.com
> >
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of >Leigh
> Harrison >Sent: Tuesday, November 29, 2005 6:04 AM
> >To: FORUM
> >Subject: DNS Disaster Recovery Question
> >
> >All,
> >
> >A customer of mine has asked me to look at a company
> called >Netnames.com.
> >
> >This is to do with using DNS for disaster recovery, i.e.,
> changing the >ip address to point at a server in a
> different data centre. >Their solution is to change the
> TTL on the customers DNS to 5 mins, you >can also log in
> to change it if need be. >
> >Have any of you service provider chaps come across this
> place? Is there >
> >an alternative/easier/cheaper solution?
> >
> >Any comments/suggestions greatly welcomed.
> >
> >LH
> >
> >_________________________________________________________
> ______________ >Subscription information may be found at:
> >http://www.groupstudy.com/list/CCIELab.html
> >
> >_________________________________________________________
> ______________ >Subscription information may be found at:
> >http://www.groupstudy.com/list/CCIELab.html
> >
> >
> >
>
Ian Stong
http://www.ccie4u.com
"Rack Rentals and Lab Scenarios starting at only $12"
support@ccie4u.com
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