On Thu, 14 May 1998, Hans Niklasson wrote:
Greetings
This is one of the actionspoints from RIPE-28, to present easy and short recommendations for setting up a DNS. I presented this for the DNS WG on RIPE-29. Any suggestions or remarks will still be very welcomed. Especially the times for the SOA records. Otherwise I recommend that we move forward to make this a RIPE-document.
Hello. As someone pointed out at RIPE-29, it would be a good idea to increase the expiration period appr four times, say 2419200, there is really no point in limiting this to one week, often the customers do not realize that their nameserver is out of order, and in one week their domain is vanished from Internet. Best regards
DNS recommendations.
By:
Hans Niklasson <hasse@swip.net> Amar Andersson <amar@telia.net>
Scope:
This documents act as a recommendation for configuring your DNS. This is NOT a requirement, only a recommendation of things to think about when setting up your DNS.
Purpose:
To decrease lame delegations and limit unecessary traffic due to resolving problems, among other things.
Records: -----------------------------------------------------------------------------
SOA The address in this field must be a valid e-mail address to the administrator for the DNS. *** It's also good practise to have role address instead of personal, ie root.. admin.. hostmaster.. (when domain-administrator is leaving your company, you only change the alias for role address).
Ex:
domain.xx. 3600 SOA dns.domain.xx admin.domain.xx.
SERIAL Serial number should follow this format: YYYYMMDDXX ( year.year.year.year.month.month.day.day.nr.nr ), where XX is the number of the latest update of the zone in the same day. (Year 2000 is near.)
Ex:
1998010101 ; serial
TTL A good balance of this will reduce unecessary traffic between nameservers.
Ex:
28800 ; refresh (8 hours) 7200 ; retry (2 hour) 604800 ; expire (7 days) 86400 ) ; minimum (1 day)
MX When pointing a domain to a mailserver/hostname, don4t forget to add a glue record ( A ) for this.
Ex:
domain.xx. 86400 MX 10 mail.domain.xx.
mail.domain.xx 86400 A 192.168.0.1
CNAME Use this with percausion. It is *not* recommended to use a CNAME for a mailservers hostname, as this can cause resolving problems and mailloops.
A A gluerecord can only point to an IP address.
PTR This is used for reverse lookup of the IP address to a hostname within the zone. Make sure that your PTR records and A records match. For each A record there has to be a PTR record, and vice versa.
More tips:
Unecessary glue data:
Don4t add unecessary glue data about hosts that is not within the zone. This can cause resolving problems if the host changes IP address.
Ex:
domain.xx. 86400 MX 10 mail.server.xx.
mail.server.xx 86400 A 192.168.0.1
Trailing dots: Don4t forget to add a "." at the end of the domain/ hostname. If this is forgotten, this will make the DNS to add the domain name to the domain/hostname again. This will cause resolving problems.
Ex:
domain.xx. 86400 MX 10 mail.domain.xx.domain.xx.
Illegal characters:
Only a-z , 0-9 and - is valid to use. All other characters is illegal and can cause the resolving to fail.
General Points:
Use the latest version of the DNS software for your platform. Check for updates regulary, as new versions has the latest solutions and information.
Additional reading and references:
RFC1537 ( RFC1912 ) ( Common DNS Operational and Configuration Errors )
"DNS & BIND 2nd Edition" by Paul Albitz & Cricket Liu from O4Reilly & Associates Inc.
ftp://ftp.ripe.net/internet-drafts/draft-ietf-dnsind-classless- inaddr-04.txt ( For reverse delegation methods for blocks smaller than /24, 256 addresses )
http://www.dns.net/dnsrd/ ( DNS Resources Directory )
/Hans Niklasson
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