DNS Workshop

1
DNS Workshop
Mark Elkins A founding member and Technical
Director of UniForum SA, Author of the COZA DNS
System, Owner of Posix Systems - a 'Large', 2nd
tier ISP, ..and has been around playing with the
Internet before it was commercially
available in South Africa.
mje_at_posix.co.za
2
Why DNS

• An IP Address has 232 or over 4 billion
  permutations
• Names are easier to remember
• HOSTS files are not scalable
• Traffic load
• Name collisions
• Consistancy
• One Machine with one IP address can have many
  different names (Virtual Web Server)

3
DNS is Scalable

• It Works (usually)
• Can be fault tolerant
• DNS allows for downward delegation of
  responsibility

4
Using BIND

• Berkeley Internet Name Domain software - Versions
• Example Lookup
• www.posix.co.za
• Nameserver Types
• None
• Cache Only
• Secondary
• Primary

'.' 'za' 'co' 'posix' 'www'
5
Setting up your own Zone

Comments /etc/ns.d/db.pearce.co.
za Last Update mje99!mje ttyp2
21 Aug 02 1507
Don't forget to change the serial Number
whenever any of the files are
changed! The format is YYYYMMDD??
Timeouts and authorities
TTL 864000 _at_ IN SOA
mje99.posix.co.za. dns-admin.posix.co.za. (
2002082100
Serial number
864000 Refresh after 10 days
(secs) 36000
Retry after 10 hours
3600000 Expire after
42 days 864000 )
Minimum TTL 10 days
6
Setting up your own Zone
Nameservers IN
NS mje99.posix.co.za. IN
NS secdns1.posix.co.za. Mail
Exchangers IN MX 0
mercury.pop.co.za. IN MX
10 secdns1.posix.co.za. IP for the
Zone IN A
160.124.208.1 Other Information
localhost IN A
127.0.0.1 ftp
IN A 160.124.208.1
webftp IN A
160.124.208.1 www
IN A 160.124.208.1


7
Named.conf entries

Primary entry zone
"pearce.co.za" type
master file
"db.pearce.co.za"
Secondary entry // Added
2002-06-06 181718 (Thu) zone
"pearce.co.za" type
slave file
"posix/sec/db.pearce.co.za"
masters
160.124.48.1



8
Setting up a Reverse Zone

/etc/ns.d/db.160.124.49 Last Update
mje99.posix.co.za!mje ttyp9 29 Apr 98 1650
Don't forget to change the serial Number
whenever any of the files are changed! The
format is YYYYMMDD?? TTL 864000 _at_
IN SOA mje99.posix.co.za.
dns-admin.posix.co.za. (
2001022809 Serial number
864000 Refresh after 10 days
(secs) 36000
Retry after 100 mins 3600000
Expire after 42 days
864000 ) Minimum TTL 10 days
IN NS
mje99.posix.co.za. IN
NS secdns1.posix.co.za. 0
IN PTR posix.co.za. 10
IN PTR headmaster.entrepreneu
rship.co.za. 11 IN PTR
tux.ukusiza.co.za. 12 IN
PTR ecom.e-way.co.za.


9
Named.conf Reverse entries

Primary zone "49.124.160.in-addr.arpa"
type master file
"db.160.124.49" Secondary
zone "49.124.160.in-addr.arpa"
type slave file
"posix/sec/db.160.124.49"
masters 160.124.48.1




10
CO.ZA Form (Part 1)



Form Header UNIFORUM S.A.
COZA Registration Office
Last Change - 02 September 1998 Domain
1a. Complete domain name pearce.co.za
1b. Action - New, Update, or
Delete (N/U/D) N Registrant and Billing
2a. Domain Owner Gary Pearce
2b. Owner Postal address P.O. Box 77305
Eldoglen 0171 2c. Owner Street
address 8 Shilling Close, Eldoglen, Centurion
2d. Cost of this application (150
50/0) 200 2e. On Account,
Invoice me or Cheque on its way (A/I/C) I
2f. Organisation to be billed or
account no. Gary Pearce 2g.
E-Mail address to send invoice to
gary_at_paceoil.co.za 2i. Inv.
Addr P.O.Box 77305 Eldoglen 0171
2j. Owner Phone No. 082 440 9635
2k. Owner Fax No. 012 658 0294
2l. Owner e-mail gary_at_paceoil.co.za


11
CO.ZA Form (Part 2)





Admin Contact 4a. Name (last,
first) Pearce, Gary 4b.
Title/position Owner 4c.
Organisation Private 4d. Postal
Address P.O.Box 77305 Eldoglen 0171
4e. Phone Number 082 440 9635
4f. Fax Number 012 658 0294 4g.
Email address gary_at_paceoil.co.za
4h. NIC assigned Handle (if known)
Technical Contact 5a. Name (last,
first) Elkins, Mark 5b.
Title/position Director 5c.
Organisation Posix Systems (Pty) Ltd
5d. Postal Address P.O. Box 73892, Lynnwood
Ridge, 0040 5e. Phone Number 012
807 0590 5f. Fax Number 012 807
5324 5g. Email address
dns-admin_at_posix.co.za 5h. NIC
assigned Handle (if known) MJE
Nameservers 6a. Primary server
FQDN mje99.posix.co.za 6b.
Primary server IP address 160.124.48.1
6e. Secondary server FQDN
secdns1.posix.co.za 6f. Secondary
server IP address 160.124.112.10

12
CO.ZA technical limitations

• One application per e-mail
• Application must be ASCII
• No Word/DOC, UU/Base-64/HTML Encoding
• Don't do ORG.ZA domains - only CO.ZA
• Need a Domain Name, only a Domain Name.
• Up to 30 Chars
• No Naked Hyphens
• No double Hyphens (Multi-language)
• All needed fields are supplied
• E-mail fields must look like valid e-mail
  addresses
• Phone Numbers must look like phone numbers
• IP Addresses must be valid
• Nameservers must be valid
• Nameserver must have a reverse
• Nameservers must be reachable
• Cross check between Zone and Nameservers must
  work

13
Potential Changes to COZA

• Removal of MX entries
• Glue - a Sticky problem
• Pre-Registration of NameServers - the .COM way
• Pro's Cons
• Registration of Nameservers in a Domain
• Pro's Cons
• Restriction to the CO.ZA Zone
• Only use 'registered' nameservers

14
Odds Ends

• Recursive search for Glue
• rat.co.za --gt ns.v-e-s.com ns1.v-e-s.com
  gt No A Records
• v-e-s.com --gt ns1.rat.co.za ns2.rat.co.za
  gt No A Records (recently changed to
  ...is.co.za)
• Nameserverless domains
• globe --gt ns.dragon-dbn.co.za.
  ns2.dragon-dbn.co.za.
• ....but there is no 'dragon-dbn.co.za'

15
Summary

• Why DNS?
• DNS is scalable
• Using BIND
• Setting up your own Zone
• named.conf entries
• Setting up a Reverse Zone
• CO.ZA application
• CO.ZA technical limitations
• Changes to how CO.ZA works
• Odds and Ends