Registration and address asignment

1

• Registration and address asignment
• DNS management
• Eugenie Staicut
• Research Institute for Informatics
• Bucharest, Romania
• CEENet 97 3-rd Network Technology Workshop
• 23-31 August 1997, Zagreb, Croatia

2
IP addresses and names

• Disadvantages of an address
• It is too long (192.162.16.201)
• It has no representation for the organization
  where we want to connect
• It is difficult to remember
• Names
• Human users prefer to use names instead of
  numbers
• A name can be associated to any device that has
  an IP address
• Example ftp.ripe.net, kyoto-u.ac.jp,
  www.cisco.com
• Advantages of names
• They make reference to an organization name
  www.ibm.com
• They are easy to remember

3
Domain Name Hierarchy
Root domain

.
Top-Level-Domains
. . . . . .
edu
com
gov
mil
net
org
ro
fr
at
jp
Second Level Domains
ici
imar
ase
pub
utt
vsat
ac
co
gv
or . . .
eunet
uni-linz
tuwien
. . . . . . .
univie
roearn ns std
cs
lmn
dsp
cc
mat
exp
itc
. . . . . .
ulise paul
phytia alpha chris
4
Domain name structures

• The root of system is unnamed
• Top level domains are
• Within the United States of America
• edu - educational institutions
• com - commercial institutions
• net - network support organizations
• gov - government agencies
• mil - military organizations
• org - organizations that dont fit in any of the
  above
• country code according to ISO-3316 (uk, de, fr,
  pl, sk, mk, md, ....)
• Flat structure
• Based on generic categories (ac, co, gv, or, nt,
  etc.)
• Based on geographical locations (waw.pl,
  poznan.pl, etc.)

5
IANA (Internet Assigned Numbers Authority)

• IANA is the overall authority for
• IP addresses
• top-level-domains
• Autonomous Systems number
• other parameters (protocol numbers, port numbers,
  etc.)
• See the file /etc/protocols on a UNIX machine
• 0 IP pseudo protocol number
• 1 ICMP
• 6 TCP
• 17 UDP
• Well known TCP ports (see the file /etc/services
  on a UNIX machine)
• 21 - FTP server
• 23 - telnet server
• 25 - SMTP mail server
• 53 - domain nameserver
• 110 - POP3 server

6
Setting up a Top-Level-Domain (TLD)

• Set up the primary nameserver for the
  top-level-domain
• Ask somebody to run secondary nameserver at
  different locations, different continents (RIPE,
  EUNET, UUNET and others could help)
• Send mail to and to
  providing the Internic domain
  template, including
• administrative contact person
• technical contact person
• primary nameserver
• secondary nameservers
• See ftp//ftp.rs.internic.net/template/domain-temp
  late.txt for a template application form
• whois program can be used to query if a
  top-level-domain is registered
• example whois -h rs.internic.net hr-dom

7
Whois -h whois.internic.net hr-dom

• Croatia / Hrvatska (Republic of) top-level domain
  (HR-DOM)
• CARNet (Croatian Academic and Research
  Network)
• SRCE, J. Marohnica bb
• 41000 Zagreb
• CROATIA
• Domain Name HR
• Administrative Contact
• Pale, Predrag (PP48) ppale_at_ETF.HR
• 38 41 629 963
• Technical Contact, Zone Contact
• Ivan, Maric (MI28) Ivan.Maric_at_SRCE.HR
• 385 (FAX) 385
• Record last updated on 27-Jan-95.
• Record created on 27-Feb-93.
• Database last updated on 22-Aug-97 043050
  EDT.
• Domain servers in listed order
• DNS.SRCE.HR 161.53.3.7
• NS1.UNIVIE.AC.AT 193.171.255.2
• NS.EU.NET 192.16.202.11

8
Obtaining an IP address

• Originally, IP numbers were assigned by the
  Global Internet Registry (known as the InterNIC).
• Today, day-to-day responsibility for assignment
  of IP addresses, Autonomous System Numbers is
  given to Internet registries (IR)
• RIPE-NCC for Europe
• APNIC for Asia and Pacific Area.
• RIPE has established local Internet Registries in
  countries in Europe
• RIPE-NCC has been delegated the following address
  ranges
• 192.162.0.0 - 192.162.255.0
• 192.164.0.0 - 192.168.255.0
• 193.0.0.0 - 193.255.255.0
• 194.0.0.0 - 194.255.255.0

9
Obtaining an IP address (continue)

• RIPE-NCC delegates blocks of numbers to local
  Internet Registry in a country
• The local Internet Registry assigns IP numbers to
  users
• The user sends his request to the local Internet
  Registry, providing information about network
  name, administrative and technical contact
  persons (try whois -h whois.ripe.net
  193.226.32.0 for an example, but follow your
  local Internet Registry instructions)
• The local Internet Registry assigns an IP number
  and register the data to RIPE database, which is
  the only authoritative registry for the status of
  a particular network number from a RIPE-NCC
  delegated block
• Requests sent by users for address space should
  be reasonable and accompanied by enough technical
  details to justify the amount of address space
  requested

10
How to query RIPE database

• Using whois
• whois -h whois.ripe.net help ripe.help
• whois -h whois.ripe.net
• word-for-search
• IP address
• person name
• domain name
• AS NUMBER
• ftp ftp.ripe.net
• gopher gopher.ripe.net
• wais wais.ripe.net
• mail to mailserv_at_ripe.net
• Query the RIPE Databe
• whois -h whois.ripe.net 161.53.0.0
• whois -h whois.ripe.net AS1755
• whois.h whois.ripe.net at
• whois -h whois.ripe.net

11
Whois -h whois.ripe.net 193.230.1.0

• inetnum 193.230.1.0 - 193.230.1.255
• netname IPA
• descr Research Institute for Automation -
  Bucharest, Romania
• country RO
• admin-c SP72-RIPE
• tech-c GM76-RIPE
• tech-c BP30-RIPE
• remarks object maintained by ro.rnc local
  registry
• notify domain-admin_at_roearn.ici.ro
• mnt-by AS3233-MNT
• changed alina_at_u1.ici.ro 960206
• changed estaicut_at_linkguide.ici.ro 970803
• source RIPE

12

• person Sanda Petrescu
• address Research Institute for Automation
• address 167 Calea Floreasca blvd., sect.1
• address Bucharest, Romania
• phone [phone]
• fax-no 40-1-3125392
• e-mail sanda_at_automation.ipa.ro
• nic-hdl SP72-RIPE
• notify domain-admin_at_roearn.ici.ro
• changed alina_at_u1.ici.ro 960206
• source RIPE

13
Whois -h whois.ripe.net at

• domain at
• descr Top Level Domain for the Republic of
  Austria
• descr managed by UniVie/ACOnet
• admin-c PR67
• tech-c WK42
• zone-c GW13-RIPE
• nserver ns1.univie.ac.at
• nserver ns2.univie.ac.at
• nserver alijku01.edvz.uni-linz.ac.at
• nserver ns.uu.net
• nserver ns.eu.net
• nserver ns.Austria.eu.net
• remarks ftp//ftp.univie.ac.at/netinfo/aconet
  /at-dom.template.ge
• remarks role mailbox for inquiries
  mailtodomain-admin_at_univie.ac.at
• mnt-by AT-DOM-MNT
• changed panigl_at_cc.univie.ac.at 960126
• changed werner_at_evolution.co.at 960719
• changed woeber_at_cc.univie.ac.at 961113
• changed Andreas.Papst_at_univie.ac.at 970219

14

• route 193.230.0.0/17
• descr RNC, Romanian National Computer
  Network for Research and Education
• origin AS3233
• mnt-by AS3233-MNT
• changed estaicut_at_linkguide.ici.ro 961021
• source RIPE

15
Autonomous System Number

• An Autonomous System Number (AS) is a set of
  routers under a single technical administration,
  using an interior gateway protocol and an
  exterior gateway protocol to route packets to
  other ASs.
• An AS is a connected group of IP networks run by
  one or more network operators which has a single
  and defined routing policy.
• AS number is a 16 bit number (65535 unique AS
  numbers).
• It is a finite amount of address space.
• Sometimes, the term AS is misunderstood and used
  for grouping together a set of prefixes which
  belong under the same administrative umbrella.
• AS number are assigned by RIPE in Europe

16
Whois -h whois.ripe.net AS6715

• aut-num AS6715
• descr Logic Telecom SA
• descr Bucharest, Romania
• as-in from AS5484 100 accept ANY
• as-in from AS6746 100 accept AS6746 AS2614
  AS6845
• as-out to AS6746 announce AS6715
• as-out to AS5484 announce AS6715 AS6746
• default AS5484 100
• admin-c CT19-RIPE
• tech-c AD17-RIPE
• mnt-by AS6715-MNT
• changed cornel_at_logicnet.ro 961122
• changed cornel_at_logicnet.ro 970804
• source RIPE

17
Domain Name Servers

• Usually host names are used in network commands
  (telnet, ftp, mail, gopher clients, www clients,
  etc. )
• Network connections always take place based on
  the IP address
• The system always converts host names to
  addresses before the network connection is made
• How to associate names with addresses?
• Host table
• Domain Name Server

18
IP datagram format
Type of Service (8 bits)
Header length
Version
Total Length (16 bits)
Identification (16 bits)
0
D
M
Fragment Offset
Time to Live
Protocol
Header Checksum
Source IP address (32 bits)
Destination IP address (32 bits)
TCP header
Data
19
Host Table

• host table is a simple text file (/etc/hosts)
  which contains associations between an IP address
  and a list of host names.
• Example
• 192.162.16.1 ciscoags1.ici.ro ciscoags1
• 192.162.16.2 roearn.ici.ro roearn
• 192.162.16.3 pcs1.ici.ro pcs1
• 192.162.16.4 std.ici.ro std
• Disadvantage
• The table should contain all the Internet hosts
  (over 10,000,000 entries)
• The table is very large
• Difficult to update when new hosts are connected
  to Internet or IP addresses are changed

20
Domain Name Server (DNS)

• Overcomes the weaknesses of the host table
• It is a distributed database system
• Host names are automatically disseminated to
  those who ask to have access

21
Internet Protocols
SNMP
NFS RPC
FTP RFC 959
RIP RFC 1058
Routing protocols EGP
Telnet RFC 854
SMTP RFC 821
DNS RFC 1035
ICMP RFC 792
TCP RFC 793
UDP RFC 768
IP
RFC 791
ARP RFC 826
X.25
PPP
Ethernet/IEEE 802.3
HDLC
SLIP
LAPB
LAN
Public telephone network
22
BIND - UNIX Name Service

• In UNIX, DNS is implemented by the Berkeley
  Internet Name Domain (BIND) software
• It is a client/server software system
• The client is called resolver it generates
  queries for domain name information that are sent
  to the server
• The server is a daemon called named.
• The domain name is actually an argument used by
  the local resolver
• The resolver is responsible for hiding the
  distribution of data among nameservers from the
  user
• The resolver is part of the operating system.

23
DNS Operation

• To establish a connection to a remore host, a
  user program sends a query to the resolover,
  asking the IP number of a specified hostname
• The resolver starts with knowledge of at least
  one nameserver
• The resolver processes a user query by asking a
  known nameserver for the information (IP for the
  remoete host)
• If the remote host is in the zone delegated to
  it, it will answer with its IP number
• The local nameservers knows the addresses of
  other nameservers
• If the remote host is in a zone for which the
  local nameserver is not delegated, queries will
  be sent to other nameservers, starting with root
  servers to find out the delegated nameserver for
  the top-level-domain, the subdomain and so on

24

• Local Host
  Remote host
• 
  
• --------- ----------
  -------- -------- --------
• user queries queries
  queries
  
• User --------------
  ---------- Known ---------- Foreign
  
• Program Resolver
  Name Name
• user responses
  responses responses
  
• --------- ----------
  -------- (zone -------- --------
• A
  A transfer)
• cache additions
  references
• V
  
• ----------
  
• cache
  --------------
• ----------
  local
• 
  data
• 
  base
• 
  (master zone

25
DNS Operation (continue)

• To minimize the answer time for the next query to
  the same host name, the nameserver caches the
  information obtained by a query the information
  cached is valid a certain time period as defined
  when that zone was configured.
• Finally, the nameserver delegated for the zone
  containing the remote host is reached and the IP
  addresses is obtained and returned to the host
  which initiated the first query

26
Remarks

• DNS is essential for a proper operation of the
  network
• If DNS fails, connections to any remote host are
  no more possible
• To allow network operation in case of failures of
  a nameserver, each nameserver (called primary
  nameserver should have at least another
  nameserver (called secondary nameserver) which
  holds a copy of the zone file
• The secondary nameserver periodically queries the
  primary nameserver whether the zone was changed.
  In case of the change, it is transferred into its
  cache and also stored in a local file, which will
  be used next time at starting up as initial data
• When data about a new host should be added to the
  DNS database, or a change of address/name should
  be done, the entry is done only on the primary
  nameserver the secondary nameserver will get it
  automatically.

27
Reverse Lookup

• When a source host establishes a connection to a
  destination host, the TCP/IP packets carry out
  only IP addresses of the source host
• For authentication, access rights or accounting
  information, the destination host wants to know
  the name of the source host
• For this purpose, a special domain id-addr.arpa
  is used
• The reverse name is obtained by reversing the IP
  number and adding the name in-addr.arpa
• Example address 192.162.16.2
• reverse name 2.16.162.192.in-addr.arpa
• Reverse domains form a hierarchical tree and are
  treated as any other Internet domain.

28
Reverse Domain Hierarchy
.arpa

.in-addr
. . . . . .
187
188
189
190
191
192
193
194
195
157
158
159
160
165
166
167
168 . . .
162
161
163
164
16
15
14
13
12
17
18
19
20
21
3
1
2
4
5
29
Hierarchy of nameservers

• Root nameserver - delegates nameservers for
  top-level-domains
• Nameserver for each top level domain - holds
  information about the top level domain, delegates
  nameservers for subdomains
• Nameserver for each subdomain
• Nameserver for each reverse domain

30
Requirements for a nameserver

• A query should be resolved as fast as possible
• It should be available 24 hours a day
• It should be reachable via fast communication
  lines
• It should be located in the central in the
  network topology
• It should run robust, without errors and
  interrupts.

31
Resolver Configuration

• The resolver configuration file /etc/resolv.conf
• Contains two types of entries
• domain defines the default domain name
• nameserver defines the IP address
  of the servers that the resolver is to query for
  domain information
• Example
• domain ici.ro
• nameserver 192.162.16.21
• nameserver 192.162.16.31
• nameserver 131.130.1.11

32
Nameserver Configuration

• File used
• named.boot
• named.ca
• named.local
• zone file
• reverse zone file

33
named.boot File

• Sets general parameters using the commands
• directory
• defines directory for all subsequent file
  references
• cache .
• Points to the cache file which contains NS
  records and A records that provide the addresses
  of the root servers
• primary
• Declares the server as primary for the specified
  domain-name and at the startup it loads the name
  server data base from the specified file-name
• secondary address
• Declares the server as secondary for the
  domain-name, specifying the primary nameserver
  from which the zone will be downloaded and stored
  in the file identified by file-name

34
Example - named.boot

• boot file for name server ns.ici.ro
• directory /var/named
• cache . named.ca
• primary ro ro.zone
• primary md
  md.zone
• primary 0.0.127.in-addr.arpa named.local
• primary 1.226.193.in-addr.arpa
  193_226_1.revzone
• secondary 226.193.in-addr.arpa 192.162.16.31
  226_193_in-addr_arpa_sec.revzone
• secondary ase.ro
  193.226.62.3 ase_ro_sec.zone
• secondary 33.226.193.in-addr.arpa 192.162.16.31
  193_226_33_sec.revzone

35
named.ca File

• Contains
• NS records to define the root servers
• A records to define the IP addresses of root
  servers
• The file containing the root servers can be
  downloaded by
• ftp from ftp.rs.internic.net in the file
  domain/named.root
• It is recommended that the root-servers file is
  downloaded once a month and make any necessary
  changes to the file named.ca

36
Example - named.ca

• Some root servers for initial startup
• . 99999999 IN NS A.ROOT-SERVERS.NET.
• 99999999 IN NS B.ROOT-SERVERS.NET.
• 99999999 IN NS C.ROOT-SERVERS.NET.
• 99999999 IN NS D.ROOT-SERVERS.NET.
• 99999999 IN NS E.ROOT-SERVERS.NET.
• 99999999 IN NS F.ROOT-SERVERS.NET.
• 99999999 IN NS G.ROOT-SERVERS.NET.
• 99999999 IN NS H.ROOT-SERVERS.NET.
• 99999999 IN NS I.ROOT-SERVERS.NET.
• A records for root nameservers, initial cache
  for the first startup of named process
• A.ROOT-SERVERS.NET. 99999999 IN A
  198.41.0.4
• B.ROOT-SERVERS.NET. 99999999 IN A
  128.9.0.107
• C.ROOT-SERVERS.NET. 99999999 IN A
  192.33.4.12
• D.ROOT-SERVERS.NET. 99999999 IN A
  128.8.10.90

37
named.local File

• It used to convert the address 127.0.01 (the
  loopback address) into the name localhost
• It is the zone file for the reverse domain
  0.0.127.in-addr.arpa
• Example named.local for server ns.ici.ro
• Each zone starts with SOA (Start Of Authority)
• _at_ IN SOA ns.ici.ro. domain-admin.roearn.ici.ro. (
• 1 serial
• 86400 refresh 24 hours
• 14400 retry 4 hours
• 2592000 expire 30 days
• 345600 ) minimum TTL 4 days
• The NS (Name Server) record defines the name of
  the nameserver
• for a domain, in this case the domain is
  0.0.127.in-addr.arpa)
• IN NS ns.ici.ro.
• The PTR (Pointer) translate an IP address into
  a hostname
• 1 IN PTR localhost.

38
Zone file for a top level domain

• Pathname /var/named/ro.zone - ns.ici.ro
• _at_ IN SOA ns.ici.ro.
  estaicut.roearn.ici.ro. (
• 97062100 Serial
• 86400 Refresh 24 hours
• 14400 Retry 4 hours
• 2592000 Expire 30 days
• 345600 ) Minimum TTL 4 days
• IN NS ns.ici.ro.
• IN NS ns1.univie.ac.at.
• IN NS ns.eu.net.
• IN NS sunic.sunet.se.
• IN NS ns.uu.net.
• IN NS sparky.arl.mil.
• IN NS ns.eunet.co.at.

39
Zone file for a top level domain (Continue)

• MX (Mail Exchganger) specifies that the mail
  for a host/domain
• should be sent to another host
• roearn.ici.ac in MX 100 roearn.ici.ro.
• adcon 86400 IN NS ns.EU.net.
• 86400 IN NS ns.Austria.EU.net.
• agir IN MX 100 ns.ici.ro.
• ase IN NS crc.ase.ro.
• IN NS infocib.ase.ro.
• IN NS ns.ici.ro.
• The A (Address) translates a hostname into an
  IP number
• crc.ase IN A 193.226.62.3
• infocib.ase IN A 193.226.62.1
• atm IN NS u2.ici.ro.
• IN NS ns.ici.ro.
• u2.ici IN A 192.162.16.31
• ns.ici IN A 192.162.16.21

40
Zone file for a subdomain

• ZONE ici.ro on u2.ici.ro
• _at_ IN SOA u2.ici.ro.
  domain-admin.roearn.ici.ro. (
• 5 Serial
• 86400 Refresh 24 hours
• 14400 Retry 4 hours
• 2592000 Expire 30 days
• 345600 ) Minimum TTL 4 days
• IN NS u2.ici.ro.
• IN NS ns.ici.ro.
• europanet IN A 193.226.46.1
• IN A 193.172.12.18
• pcrt1 IN A 192.162.16.1

41
Zone file for a subdomain (Continue)

• roearn IN A 192.162.16.2
• in hinfo Vaxserver-3100 VMS
• in wks 192.162.16.2 tcp telnet ftp
  smtp
• in wks 192.162.16.2 udp domain
• pcs3 IN A 192.162.16.3
• std IN A 192.162.16.4
• rtd2 IN A 192.162.16.6
• IN A 193.226.2.192
• rticerp IN A 192.162.16.8
• decrt1 IN A 192.162.16.11
• cisco1ici IN A 192.162.16.12
• indis IN A 192.162.16.30
• CNAME (Canonical Name) defines an allias
  (nickname) for a host
• www IN CNAME indis.ici.ro.

42
Reverse zone file for 226.193.in-addr.arpa domain

• ZONE 226.193.in-addr.arpa on u2.ici.ro
• _at_ IN SOA u2.ici.ro.
  domain-admin.roearn.ici.ro. (
• 8 Serial
• 86400 Refresh 24 hours
• 7200 Retry 2 hours
• 604800 Expire
• 86400 ) Minimum TTL 24 hours
• IN NS u2.ici.ro. ns for
  226.193.in-add.arpa
• IN NS ns.ici.ro. ns for
  226.193.in-add.arpa
• IN NS ns.ripe.net.
• 1 IN NS ns.ici.ro. ns for
  1.226.193.in-add.arpa
• IN NS ns1.univie.ac.at. ns for
  1.226.193.in-add.arpa

43
Reverse zone file for 226.193.in-addr.arpa domain
(Continue)

• 3 IN NS ns.ici.ro. ns for 3.226.193.in-add.arp
  a
• IN NS ns1.univie.ac.at. ns for
  3.226.193.in-add.arpa
• 8 IN NS tempus0.utt.ro. ns for
  8.226.193.in-add.arpa
• IN NS ns.ici.ro. ns for 8.226.193.in-add.arpa
  
• 9 IN NS tempus4.cs.utt.ro. ns for
  9.226.193.in-add.arpa
• IN NS tempus0.utt.ro. ns for
  9.226.193.in-add.arpa
• IN NS u2.ici.ro. ns for 9.226.193.in-add.arpa
  
• 19 IN NS utmures.uttgm.ro. ns for
  19.226.193.in-add.arpa
• IN NS pub.pub.ro. ns for 19.226.193.in-add.ar
  pa
• 30 IN NS cpcsat.sfos.ro. ns for
  30.226.193.in-add.arpa
• IN NS ns.pipex.net. ns for
  30.226.193.in-add.arpa
• IN NS ns.uu.net. ns for 30.226.193.in-add.arp
  a
• 33 IN NS u2.ici.ro. ns for 33.226.193.in-add.a
  rpa
• IN NS ns.ici.ro. ns for 33.226.193.in-add.arp
  a

44
Reverse zone files for 33.226.193.in-addr.arpa
domain

• ZONE 33.226.193.in-addr.arpa on u2.ici.ro
• _at_ IN SOA u2.ici.ro.
  domain-admin.roearn.ici.ro. (
• 8 Serial
• 36000 Refresh 10 hours
• 7200 Retry 2 hours
• 604800 Expire
• 86400 ) Minimum TTL
• IN NS u2.ici.ro.
• IN NS ns.ici.ro.
• 1 IN PTR alpha.rmri.ro. name associated with
  193.226.33.1
• 2 IN PTR cisco.rmri.ro. name associated with
  193.226.33.2

45
Starting named

• After constructing the required files, named is
  started using the command
• named -d level -p port -b bootfile
• with the options
• -d debugging level
• -p port (default is UDP/TCP port 53)
• -b configuration file (the default is
  /etc/named.boot)
• Normally the named is started at boot time from a
  startup script file

46
named signaling processing

• SIGHUP
• Causes named to re-read the named.boot file and
  reload the nameserver database
• SIGINT
• Causes named to dump its cache to
  /var/named_dump.db
• SIGUSR1
• Turn on debugging (output debugging data to
  /var/tmp/named.run)
• SIGUSR2
• Turn off debugging

47
Debugging DNS

• Tools
• ping
• traceroute
• telnet 53
• nslookup

48
Checking DNS using nslookup

• nslookup commands
• server set the server to be
  queriedset type NS queries NS
  resourcesset type SOA queries SOA
  resourcesset type A queries A
  resourcesset type MX queries MX
  resourcesset type CNAME queries CNAME
  resourcesset type PTR queries PTR
  resourcesset type ANY queries ANY
  resourcesls lists the
  zonels
  gets the zone into the
• fileview
  views the file
• nslookup
• set typeany
• workshop.carnet.hr.
• carnet.hr.
• hr.
• ls workshop.carnet.hr file1
• view file1 You can check
  other domains, known to you.

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Checking DNS using host

• host !you will get the help informationhost
  ! you will get IP address for
  host sun1.workshop.carnet.hr
• host ftp.univie.ac.at
• host www.microsoft.com
• host ! you will get name for
  
• host 161.53.74.11
• host 131.130.1.72
• host 207.68.137.65
• host -t ! query for a specific
  type of records (NS, SOA, MX, A, CNAME,
  PTR)
• host -t ns workshop.carnet.hr host -t soa
  workshop.carnet.hr
• host -a !query for all record of a
  domain, verbose mode host -a carnet.hr host -a
  hr. Host -a workshop.carnet.hrhost -l a
  !list all the zone for a domain host -l
  -a workshop.carnet.hrCheck other domains, which
  are known to you!

50
REFERENCES

• Craig Hunt, TCP/IP Network Administration,
  OReilly Associates, Inc., Sebastopol, 1993
• P. Beertema, Common DNS Data File Configuration
  Errors, RFC 1537, Oct. 1993
• J. Postel, Domain Name System Structure and
  Delegation, RFC 1591, March 1994
• A. Romav, Taking care of Your Domain, RIPE-114,
  May 1994
• J. Hawkinson, Guidelines for creation, selection
  and registration of an Autonomous System (AS),
  Internet-Draft, May 1995
• Internetworking Technology Overview, Cisco
  Systems, Inc., 1993
• Booktexts of the 4th Network Seminar and
  Intensive Course for Scientists and Network
  Managers from Central Europe, Feb. 1993, Vienna
  University Computer Center
• Booktexts of Network Technology Workshop,
  National Network Management Track, Honolulu, June
  1995
• M. Lottor, Domain Administrators Operations
  Guide, RFC 1033
• RFC 1032, RFC 1034, RFC 1035