10-22-2015
Dns is just a lookup table. And yes, it can return multiple records for a query. It's supposed to provide a cheap man's round robin on the returns (but you never know how many things are doing lookups, so sort of random). You can run your own DNS server, point to it and lie (if you want) about being authoritative for "whatever" (e.g. unix.com). Then all clients can be tricked into seeing your mappings for unix.com if they use your "tricky" DNS. You could cache other non-housed requests.... so you DNS would be "complete", but doing a tricky override for "whatever" you wanted to lie about. Hopefully this scares you a bit and it's a good segue into DNSSEC, etc...
Do a query, pick the first answer. That's how it's normally done.
Queries for records you don't house start at the root (of all... the root servers... "dot" if you will), then goes to what we call the TLDs and so on. If you own a registered domain, you can associate a DNS to it to build the relationship required (if you do this without cooperation of the holder of the parent zone this won't work, the parent zone has to know how to delegate requests to your server... sometimes the parent zone will stand authoriatative for your zone by default and they'll handle servicing your records... but normallly, you'd tell them about your server and that it will now stand authoritative for those zone (your registered domain).
Oh... and there is some caching going on the speed this lookups up quite a bit.. but the root servers get hit pretty hard.
There are good books out there... I recommend you look at the documentation at:
https://www.isc.org/support/
10 More Discussions You Might Find Interesting
1. UNIX for Advanced & Expert Users
Hi everyone ...
I want to configure my dns in order to answer to two differents url, for example when the people put www.mywebsite.com.mx or put mywebsite.com.mx ( without www ) my dns could send all the request to the same page an example of this is microsoft.com and www.microsoft.com.
... (4 Replies)
Discussion started by: lusifer
4 Replies
2. Solaris
Hi,
I got solaris 10 installed on a E250 and i am expericing issues resolving dns.
from some research i think it's becuase where i haven't set-up NIS and i don't intend too as i am just setting up a box to poke communigate pro.
Any help or advice please?
Thanks in advance
Alan (1 Reply)
Discussion started by: e250user
1 Replies
3. UNIX for Dummies Questions & Answers
Hello,
I am new to Solaris.
I am using stand alone Solaris 10.0 for test/study purpose and connecting to internet via an ADSL modem which has DHCP server. My Solaris is working on VMWare within winXP. My WinXP and Solaris connects to internet by the same ADSL modem via its DHCP at the same... (1 Reply)
Discussion started by: XNOR
1 Replies
4. UNIX for Advanced & Expert Users
I've got an old v880 running Sol10 that is going to another location. When the system moves, the domainname in resolv.conf will change also. My DBA's are going through the steps of installing Oracle on the box and they want the install program to resolve the hostname is if the box were already in... (2 Replies)
Discussion started by: bluescreen
2 Replies
5. UNIX for Advanced & Expert Users
I'd like to get some opnions on choosing DNS server:
Windows DNS vs Linux BIND comparrsion:
1) managment, easy of use
2) Security
3) features
4) peformance
5) ??
I personally prefer Windows DNS server for management, it supports GUI and command line. But I am not sure about security... (2 Replies)
Discussion started by: honglus
2 Replies
6. Emergency UNIX and Linux Support
Hi All,
So we added a new HP-UX 11.31 machine. Copied OS via Ignite-UX (DVD)over from this machine called machine_a. It was supposed to be named machine_c. And it is when you log in...however when I'm in the ILO console before logging in, it says:
It should say:
What gives? And how do... (4 Replies)
Discussion started by: zixzix01
4 Replies
7. Red Hat
In my work env we have a lots of hosts. most all the hosts are in similar hostnames for eg cluster11.data.corp.sb1.uni.com, med123.data.corp.sk1.uni.com, also we have some server is colo network which have the host name like cluster11.data.colo.sb1.uni.com
Please help me to make the... (2 Replies)
Discussion started by: unimaxlin
2 Replies
8. Red Hat
Hello,
Having issue resolving DNS using the IP address.
Using the server Name it resolves fine.
Was wondering if there is any configuration issue.
# nslookup xxxxxxxx01
Server: Primary DNS IP
Address: Primary DNS IP#53
Name: xxxxxxxx01.local domain
Address: x.y.z.123
# nslookup... (1 Reply)
Discussion started by: ikn3
1 Replies
9. UNIX for Advanced & Expert Users
deleted (0 Replies)
Discussion started by: hce
0 Replies
10. IP Networking
I have vmware on my windows PC ( hostname : acer ).
vmware has RHEL 7 ( hostname : rhel7 ) installed recently.
RHEL IP configuration
IP : 192.168.5.128
Netmask : 255.255.255.0
ssh to rhel7 works from acer using putty
resolve.conf
cat /etc/resolv.conf
nameserver 192.168.5.1
host... (12 Replies)
Discussion started by: hiten.r.chauhan
12 Replies
HOST(1) BSD General Commands Manual HOST(1)
NAME
host -- DNS lookup utility
SYNOPSIS
host [-aCdilrsTvw46] [-c class] [-N ndots] [-R number] [-t type] [-W wait] name [server]
DESCRIPTION
host is a simple utility for performing DNS lookups. It is normally used to convert names to IP addresses and vice versa.
name is the domain name that is to be looked up. It can also be a dotted-decimal IPv4 address or a colon-delimited IPv6 address, in which
case host will by default perform a reverse lookup for that address.
When name is not provided, host prints a short summary of it's usage.
server is an optional argument which is either a domain name or an IP address of the name server that host should query instead of the server
or servers listed in /etc/resolv.conf. When server is a domain name, system resolver is used to obtain it's address.
Supported options:
-a Make a verbose query of type ANY. Equivalent to -v -t ANY.
-C Query for SOA records for zone name from all of it's authoritative name servers. The list of name servers is obtained via NS query
for name.
-c class
Perform DNS query of class class. Recognized classes are IN (Internet), CH (Chaosnet), HS (Hesiod), NONE, ANY and CLASSN (where N is
a number from 1 to 255). Default is IN.
-d Produce verbose output. This is a synonym for -v, and is provided for backward compatibility.
-i Use IP6.INT domain for reverse lookups of IPv6 addresses (as defined in RFC1886; note that RFC4159 deprecates IP6.INT). By default
IP6.ARPA is used.
-l List all NS, PTR, A and AAAA records in zone name by performing a zone transfer (AXFR). You can combine this option with -a to print
all records, or with -t to only print specific ones.
-N ndots
Consider names with at least this many dots as absolute. That is, try to resolve them directly before consulting domain or search
options from /etc/resolv.conf.
-r Perform non-recursive query to the name server by clearing RD (``recursion desired'') bit of the query.
-R number
Retry this many times when a query does not receive an answer in time. The default is 1 retry. If number is negative or zero, 1 is
used instead.
-s Report SERVFAIL responses as they are, do not ignore them.
-T Query name server over TCP. By default UDP is used, except for AXFR and IXFR queries, which require TCP. host will also retry UDP
queries in TCP mode if the UDP response was truncated (i.e. had TC bit set).
-t type
Perform DNS query of type type, which can be any standard query type name (A, CNAME, MX, TXT, etc), a wildcard query (ANY), or TYPEN,
where N is a number from 1 to 65535. For IXFR (incremental zone transfer) queries the starting serial number can be specified by
appending an equal sign followed by the number (e.g. -t IXFR=12345678).
The default is to query for A, AAAA, and MX records, unless -C or -l options are given (in which case SOA or AXFR queries are made)
or name is a valid IP address (in which case reverse lookup using PTR query is performed).
-v Produce verbose output.
-w Wait forever (or for a very long time) for response from the name server.
-W wait
Wait this many seconds for a reply from name server before timing out. If wait is negative or zero, value of 1 is used. The default
is to wait 10 seconds for TCP connections, and 5 seconds for UDP (both are subject to retries, see option -R).
-4 Only use IPv4 transport.
-6 Only use IPv6 transport.
FILES
/etc/resolv.conf
SEE ALSO
drill(1), resolv.conf(5)
COMPATIBILITY
host aims to be reasonably compatible with 'host' utility from BIND9 distribution, both in supported options and in produced output. Here is
a list of known notable differences:
o Debugging options (-D and -m) are not supported.
o Query class CLASS0 and type TYPE0 are not supported.
o Backslashes in domain names are treated especially.
o The maximum of 255 retries (option -R) are supported.
o Some resource records are formatted differently. For example, RRSIG and DNSKEY records are displayed without spaces in them.
o When parsing /etc/resolv.conf commands sortlist and options are ignored. When multiple search and/or domain commands are present, host
first uses the last domain command, and then all of search commands, while 'host' from BIND9 uses whatever command was specified last.
o Multi-packet zone transfers are not supported; only the first response packet is printed.
o 'Pseudosection TSIG' is missing from verbose packet output.
AUTHORS
Vitaly Magerya <magv@tx97.net>
BSD
Aug 27, 2012 BSD