From: Leigh Harrison (ccileigh@gmail.com)
Date: Tue Nov 29 2005 - 11:19:39 GMT-3
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
>
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