RE: [lug-nuts] DNS Problem

From: Lancashire, Andrew (LancashireA@sutterhealth.org)
Date: Mon Jan 10 2000 - 10:11:53 PST


It is possible to have multiple A records for the same host.

check out www.ibm.com

$nslookup www.ibm.com
Server: gnsc3ms.sutterhealth.org
Address: 10.1.50.25
Non-authoritative answer:
Name: www.ibm.com
Addresses: 204.146.81.99, 204.146.80.99

 ANSWERS:
    -> www.ibm.com
        type = A, class = IN, dlen = 4
        internet address = 204.146.81.99
        ttl = 23315 (6h28m35s)
    -> www.ibm.com
        type = A, class = IN, dlen = 4
        internet address = 204.146.80.99
        ttl = 23315 (6h28m35s)

and our beloved

$nslookup www.microsoft.com
Server: gnsc3ms.sutterhealth.org
Address: 10.1.50.25
Non-authoritative answer:
Name: microsoft.com
Addresses: 207.46.131.137, 207.46.131.28, 207.46.131.30, 207.46.130.14
          207.46.130.149, 207.46.130.150, 207.46.130.45
Aliases: www.microsoft.com

QUESTIONS:
        microsoft.com, type = A, class = IN
    ANSWERS:
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.130.150
        ttl = 9595 (2h39m55s)
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.130.45
        ttl = 9595 (2h39m55s)
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.131.137
        ttl = 9595 (2h39m55s)
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.131.28
        ttl = 9595 (2h39m55s)
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.131.30
        ttl = 9595 (2h39m55s)
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.130.14
        ttl = 9595 (2h39m55s)
    -> microsoft.com
        type = A, class = IN, dlen = 4
        internet address = 207.46.130.149
        ttl = 9595 (2h39m55s)

The example with IBM shows the 2 A records. www.microsoft.com is an alias
to microsoft.com which as you can see has many A records. This allows for
high availability and round robin of all the hosts, since the cost is all
the same.

Andrew
-----Original Message-----
From: Sean-Paul Rees [mailto:sean@dreamfire.net]
Sent: Saturday, January 08, 2000 2:59 PM
To: lug-nuts@saclug.org
Subject: [lug-nuts] DNS Problem

I have DNS setup on my network server at home. A friend of mine says
that having two+ A records per IP breaks a standard. However, I disagree
with him.

Any ideas?

Cheers,
Sean
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