RE: OT: DNS Question
- From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Fri, 23 Sep 2005 11:22:30 -0500
Hi Shawn,
Good points. And then there's the habit of the Windows DNS client to
suppress addresses that don't work for X number of minutes, even if
there was a momentary connection problem.
Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://spaces.msn.com/members/drisa/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls
> -----Original Message-----
> From: Quillman Shawn (RBNA/CSA1) *
> [mailto:Shawn.Quillman@xxxxxxxxxxxx]
> Sent: Friday, September 23, 2005 11:09 AM
> To: [ISAserver.org Discussion List]
> Subject: [isalist] RE: OT: DNS Question
>
> http://www.ISAserver.org
>
>
> Keep in mind that in general DNS round-robin gets flaky at the
> application level since it's up to the application to determine how it
> handles resolution responses. If the app don't know
> round-robin you'll
> get incosistent results at best, and you know how many
> developers are in
> tune with networking theories and security...
>
> For example:
> host1.blah.com. IN A 192.168.0.1
> host1.blah.com. IN A 192.168.0.2
>
> Query 1 for host1.blah.com returns:
> 192.168.0.1,192.168.0.2
>
> Query 2 for host1.blah.com returns:
> 192.168.0.2,192.168.0.1
>
> Query 3 returns
> 192.168.0.1,192.168.0.2
>
> Etc.
>
> Say 192.168.0.1 goes down, a client's resolver caches that
> response, AND
> the app don't know round-robin. Regardless of the state of
> 192.168.0.2,
> the client's hosed until either 192.168.0.1 comes back up or
> the TTL on
> the record lapses.
>
> RR has certainly been around long enough. In most cases, in my
> experience anyway, it's only been useful to make sure that at
> least some
> people don't lose access. I'd agree that you're relatively
> safe in the
> mail world since mail's such a commodity service and is so in bed with
> DNS, but definitely play with it first :) And maybe keep low TTL's on
> the RR records. You can always then go in and whack the one record
> whose host is down if necessary to force all responses to
> resolve to the
> host that's up.
>
> >-----
> >Robert Bosch Corporation
> >Technical Systems Analyst (RBNA/CSA1)
> >Corporate Sales Reporting Systems
> >38000 Hills Tech Drive - Farmington Hills, MI 48331 - USA
> >phone: 1 (248) 553-1164 fax: 1 (248) 848-6969
> >shawn.quillman@xxxxxxxxxxxx
> >http://www.bosch.us
>
> -----Original Message-----
> From: Steve Moffat [mailto:steve@xxxxxxxxxx]
> Sent: Friday, September 23, 2005 11:41 AM
> To: [ISAserver.org Discussion List]
> Subject: [isalist] RE: OT: DNS Question
>
> http://www.ISAserver.org
>
> Cool...thats what I thought
>
> Thanks
>
> -----Original Message-----
> From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx]
> Sent: Friday, September 23, 2005 12:23 PM
> To: ISA Mailing List
> Subject: [isalist] RE: OT: DNS Question
>
> http://www.ISAserver.org
>
> Hi Steve,
>
> You can create two Host (A) records for mail.bldc.com.
>
> The create an MX record for mail.bldc.com.
>
> Enable DNS RR on the DNS server.
>
> That should do it, unless this capsicum has gone to my brainium, borax
> and abominable cavity.
>
> Thomas W Shinder, M.D.
> Site: www.isaserver.org
> Blog: http://spaces.msn.com/members/drisa/
> Book: http://tinyurl.com/3xqb7
> MVP -- ISA Firewalls
>
>
>
> > -----Original Message-----
> > From: Steve Moffat [mailto:steve@xxxxxxxxxx]
> > Sent: Friday, September 23, 2005 10:14 AM
> > To: [ISAserver.org Discussion List]
> > Subject: [isalist] OT: DNS Question
> >
> > http://www.ISAserver.org
> >
> > Normally, I'm quite good at DNS, (STFU Greggo....:), but I
> cant get my
>
> > head around this one...:)
> >
> > No ISA involved yet....it's on the cards.
> >
> > Client has 1 dedicated line and 1 ADSL line. Heh heh not a load
> > balancing or teaming question.
> >
> > Dedicated line has an fqdn of mail.bldc.com
> >
> > ADSL line has an fqdn of mail2.bldc.com (Static IP)
> >
> > Now...I want to be able to resolve mail.bldc.com to both
> IP's, is this
>
> > possible in DNS, externally hosted?.....so that if one line
> is down,
> > it'll go to the other.
> >
> > Thanks
> >
> > Steve
> >
> > The correct technical term for haggis stalking is "havering".
> >
> >
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> The correct technical term for haggis stalking is "havering".
>
>
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