Tuts4Tech » DNS

How to flush your dns cache

Duffy — Sat, 08 Aug 2009 02:01:51 +0000

Windows

Firstly open a cmd box by going to start > run > cmd
Then flush your dns by running the following:
```
ipconfig /flushdns
```

OSX

Open your terminal
Run the following command:
```
dscacheutil -flushcache
```

Linux

Just run the following:
```
/etc/init.d/nscd restart
```

Setting up a DNS Server for your LAN Network

Duffy — Fri, 08 May 2009 10:49:58 +0000

This tutorial will show you how to configure bind9 on debian to be a dns server for your LAN network.

Install bind9 and some DNS utilities
```
apt-get install bind9 dnsutils
```

Set your systems hostname

echo "server.home.local" > /etc/hostname

then edit /etc/hosts so it looks like this

127.0.0.1       localhost.localdomain   localhost
192.168.1.2    server.home.local        server
# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

change you DNS servers by editing /etc/resolv.conf
```
nano /etc/resolv.conf
```
it should look something like this:
```
search home.local
nameserver 192.168.1.2
```
Creating a Zone

The zone files are the most important part of the BIND system. They hold all the information as to what hostname goes to an IP. to get started edit /etc/bind/named.conf.local
```
nano /etc/bind/named.conf.local
```
and then add the following:
```
zone "home.local" {
        type master;
        file "home.local";
};

zone "1.168.192.in-addr.arpa" {
        type master;
        file "192.168.1";
};
```

Now we need to create the zone file in /var/cache/bind/home.local

nano /var/cache/bind/home.local

and add the following:

$TTL 604800
@ IN SOA server.home.local. sysadmin.home.local. (
                2008080101      ;serial
                04800           ;refresh
                86400           ;retry
                2419200         ;expire
                604800          ;negative cache TTL
                )
@       IN      NS      server.home.local.
@       IN      A       192.168.1.2
@       IN      MX      10      server.home.local.
server  IN      A       192.168.1.2
www     IN      CNAME   server
desktop	IN	A	192.168.1.3
printer	IN	A	192.168.2.4
laptop	IN	A	192.168.2.5

Now we need to create the reverse DNS zone file to do so we need to create /var/cache/bind/192.168.1

nano /var/cache/bind/192.168.1

and add the following:

$TTL 604800
@ IN SOA server.home.local. sysadmin.home.local. (
                2008080101      ;serial
                604800          ;refresh
                86400           ;retry
                2419200         ;expire
                604800          ;negative cache TTL
                )
@       IN      NS      server.home.local.
@       IN      A       192.168.1.2
2	IN	PTR	server.home.local.
3	IN	PTR	desktop.home.local.
4	IN	PTR	printer.home.local.
5	IN	PTR	laptop.home.local.

We now need to set DNS servers to forward to so edit /etc/bind/named.conf.options

nano /etc/bind/named.conf.options

and add the following

forwarders {
                208.67.222.222; // your isps dns server
                208.67.220.220; // your isps dns server
        };

Now we need to restart bind9 and test it

/etc/init.d/bind9 restart

dig home.local

you should see the following

; < <>> DiG 9.3.4 < <>> home.local
;; global options:  printcmd
;; Got answer:
;; ->>HEADER< <- opcode: QUERY, status: NOERROR, id: 54950
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;home.local.                    IN      A

;; ANSWER SECTION:
home.local.             64800   IN      A       192.168.1.2

;; AUTHORITY SECTION:
home.local.             64800   IN      NS      server.home.local.

;; ADDITIONAL SECTION:
server.home.local.        64800   IN      A       192.168.1.2

;; Query time: 1 msec
;; SERVER: 192.168.1.2#53(192.168.1.2)
;; WHEN: Tue Aug  5 09:33:40 2008
;; MSG SIZE  rcvd: 79

Configure all computers in your network to use 192.168.1.2 as there dns server and you should be good to go

Finding out the subdomains of a domain

Duffy — Thu, 02 Apr 2009 12:14:05 +0000

1. First off you need to get a program called dig
for debian based Operating systems you can do

apt-get install dnsutils

a windows version can be downloaded from here

2. Find out the name servers of the domain this can be done by typing

dig ns

3. Now you query the Nameserver to output the subdomains

dig @  axfr

4. You should now have a listing of all the subdomains :)

Example:

root@duffys-place:~# dig ns duffys-place.co.cc

; < <>> DiG 9.5.1-P1 < <>> ns duffys-place.co.cc
;; global options:  printcmd
;; Got answer:
;; ->>HEADER< <- opcode: QUERY, status: NOERROR, id: 48938
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;duffys-place.co.cc.            IN      NS

;; ANSWER SECTION:
duffys-place.co.cc.     43180   IN      NS      ns3.co.cc.

;; Query time: 23 msec
;; SERVER: 212.113.0.3#53(212.113.0.3)
;; WHEN: Thu Apr  2 13:12:59 2009
;; MSG SIZE  rcvd: 54

root@duffys-place:~# dig @ns3.co.cc duffys-place.co.cc axfr

; <<>> DiG 9.5.1-P1 < <>> @ns3.co.cc duffys-place.co.cc axfr
; (1 server found)
;; global options:  printcmd
duffys-place.co.cc.     86400   IN      SOA     ns.duffys-place.co.cc. root.duffys-place.ns.co.cc. 2009030300 28800 7200 604800 3600
duffys-place.co.cc.     86400   IN      NS      ns3.co.cc.
duffys-place.co.cc.     86400   IN      A       88.151.87.96
duffys-place.co.cc.     86400   IN      MX      10 mail1.duffys-place.co.cc.
files.duffys-place.co.cc. 3600  IN      CNAME   cid-d037be1f66fbe46e.skydrive.live.com.
home.duffys-place.co.cc. 86400  IN      A       88.151.87.116
mail.duffys-place.co.cc. 86400  IN      CNAME   ghs.google.com.
mail1.duffys-place.co.cc. 86400 IN      CNAME   aspmx.l.google.com.
paste.duffys-place.co.cc. 86400 IN      CNAME   duffys-place.co.cc.
shane.duffys-place.co.cc. 86400 IN      CNAME   duffys-place.co.cc.
sms.duffys-place.co.cc. 86400   IN      CNAME   duffys-place.co.cc.
usermin.duffys-place.co.cc. 86400 IN    A       88.151.87.98
webmin.duffys-place.co.cc. 86400 IN     A       88.151.87.97
www.duffys-place.co.cc. 86400   IN      CNAME   duffys-place.co.cc.
duffys-place.co.cc.     86400   IN      SOA     ns.duffys-place.co.cc. root.duffys-place.ns.co.cc. 2009030300 28800 7200 604800 3600
;; Query time: 308 msec
;; SERVER: 118.219.232.169#53(118.219.232.169)
;; WHEN: Thu Apr  2 13:13:06 2009
;; XFR size: 15 records (messages 1, bytes 442)

Please Note This Will Only Work On Some Nameservers