dhcp server & client objectives –to learn how to setup dhcp servers contents –download and...

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DHCP server & Client Objectives to learn how to setup dhcp servers Contents Download and Install The DHCP Package The /etc/dhcpd.conf File Upgrading Your DHCP Server How to get DHCP started Modify Your Routes for DHCP on Linux Server Configuring Linux clients to use DHCP Simple DHCP TroubleshootingPracticals working with TCP/IP utilities and files

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Page 1: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

DHCP server & Client

• Objectives– to learn how to setup dhcp servers

• Contents– Download and Install The DHCP Package

– The /etc/dhcpd.conf File

– Upgrading Your DHCP Server

– How to get DHCP started

– Modify Your Routes for DHCP on Linux Server

– Configuring Linux clients to use DHCP

– Simple DHCP TroubleshootingPracticals

– working with TCP/IP utilities and files

Page 2: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

Download and Install The DHCP Package

• You have three ways to install DHCP server on RedHat– With yum/up2date (install sample config and prepare lease data base)

– RPM (Simply install it, togeather with sample config)

– You need at least RPM-package dhcp-server if you download manually

– TAR-BALL (Allways latest version, the ISC standard dhcp, manual work)

• Getting the DHCP server with yum– Will download and start configure DHCP

• Installing from RPM’s

• You can also obtain dhcp sources directly from ISC

The version rpm number is dhcp-3.0.2-6 in our example, and 3.0.3 for the tar ball.

# yum install dhcp-server# yum install dhcp-server

# rpm –ivh dhcp-3.0.2-6.i586.rpm# rpm –ivh dhcp-server-3.0.2-6.i586.rpm

# rpm –ivh dhcp-3.0.2-6.i586.rpm# rpm –ivh dhcp-server-3.0.2-6.i586.rpm

# cd /usr/local/src# wget ftp://ftp.isc.org/isc/dhcp/dhcp-3.0.3.tar.gz

# cd /usr/local/src# wget ftp://ftp.isc.org/isc/dhcp/dhcp-3.0.3.tar.gz

Page 3: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

• Sample dhcpd.conf file:/usr/share/doc/dhcp-<version-number>/dhcpd.conf.sample

Their version number is dhcp-3.0pl1-23 in this example

• Begin with the sample configuration file

• Basic file format

The /etc/dhcpd.conf File basics

# cp /usr/share/doc/dhcp-3.0pl1-23/dhcpd.conf.sample \  /etc/dhcpd.conf

# cp /usr/share/doc/dhcp-3.0pl1-23/dhcpd.conf.sample \  /etc/dhcpd.conf

subnet 192.168.1.0 netmask 255.255.255.0 { default-lease-time 86400; max-lease-time 86400;option routers 192.168.1.100;option log-servers 192.168.1.100;option broadcast-address 192.168.1.255;option domain-name-servers 192.168.1.100, 80.84.37.3;option nntp-server 192.168.1.100;range 192.168.1.201 192.168.1.220; }

subnet 192.168.1.0 netmask 255.255.255.0 { default-lease-time 86400; max-lease-time 86400;option routers 192.168.1.100;option log-servers 192.168.1.100;option broadcast-address 192.168.1.255;option domain-name-servers 192.168.1.100, 80.84.37.3;option nntp-server 192.168.1.100;range 192.168.1.201 192.168.1.220; }

Page 4: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

The /etc/dhcpd.conf File fix/denial

• Deliver fixed address to a host

• Dont do DHCP on all interfaces/subnets if multihomed

• TFTP boot server and boot loader file

subnet 80.84.37.0 netmask 255.255.255.240 { not authoritative; }

subnet 80.84.37.0 netmask 255.255.255.240 { not authoritative; }

host printer { hardware ethernet 00:50:DA:38:CE:23; fixed-address 192.168.1.64; option domain-name-servers 192.168.1.100; option broadcast-address 192.168.1.255; option domain-name "printer.ikea.se";}

host printer { hardware ethernet 00:50:DA:38:CE:23; fixed-address 192.168.1.64; option domain-name-servers 192.168.1.100; option broadcast-address 192.168.1.255; option domain-name "printer.ikea.se";}

next-server 192.168.1.60; # tftp-serverfilename "pxelinux.0"; # bootloaderhost brutebert { hardware ethernet00:B0:D0:39:63:8C; }

next-server 192.168.1.60; # tftp-serverfilename "pxelinux.0"; # bootloaderhost brutebert { hardware ethernet00:B0:D0:39:63:8C; }

Page 5: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

Dynamic DNS & DHCP

• This is not the full story, DNS is also needed– You will need a DNS in order to update zonefiles

• Main entries in /etc/dhcpd.conf

• You also need one authorized key to allow updates

• These entries comes before any subnet declaration

authoritative; ddns-update-style interim;ddns-domainname "radio.ing-steen.se";update-static-leases on;

authoritative; ddns-update-style interim;ddns-domainname "radio.ing-steen.se";update-static-leases on;

key "DHCP-UPDATER"{ algorithm HMAC-MD5; secret ”<keydata>";}

key "DHCP-UPDATER"{ algorithm HMAC-MD5; secret ”<keydata>";}

Page 6: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

Dynamic DNS & DHCP

• The Forward and Reverse name Zone-files to update– They came after the ddns entries in same file.

– Zones must be specified to the DHCP

• Last comes the standard subnet declaration, like on page 3 with this added to it

zone radio.ing-steen.se.{ primary 172.16.0.5; key DHCP-UPDATER;}

zone radio.ing-steen.se.{ primary 172.16.0.5; key DHCP-UPDATER;}

zone 16.172.in-addr.arpa.{ primary 172.16.0.5; key DHCP-UPDATER;}

zone 16.172.in-addr.arpa.{ primary 172.16.0.5; key DHCP-UPDATER;}

authoritative;get-lease-hostnames true; do-forward-updates true; allow unknown-clients; ddns-updates on;

authoritative;get-lease-hostnames true; do-forward-updates true; allow unknown-clients; ddns-updates on;

Page 7: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

Upgrading Your DHCP Server

• When updatingLook in header of sample file: /usr/share7doc/dhcp<version>/dhcpd.conf.sample

Add those lines in your existing /etc/dhcpd.conf file

ddns-update-style interim # Redhat Version 8.0+ignore client-updates # Fedora Core 1+

ddns-update-style interim # Redhat Version 8.0+ignore client-updates # Fedora Core 1+

Page 8: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

How to get DHCP started

• DHCPD is depending on /var/lib/dhcp/dhcpd.leasesYou might need to erase existing lease files and create an empty:

dhcpd.leases contain leases database format when in action:

• Starting the dhcpd server

• Stoppinig and Reloading the server

# rm –f /var/lib/dhcp/dhcpd.leases# touch /var/lib/dhcp/dhcpd.leases

# rm –f /var/lib/dhcp/dhcpd.leases# touch /var/lib/dhcp/dhcpd.leases

lease 172.16.0.67 { starts 0 2004/09/05 04:41:09; ends 1 2004/09/06 04:41:09; hardware ethernet 00:0d:93:83:8a:8e; uid 01:00:0d:93:83:8a:8e;}

lease 172.16.0.67 { starts 0 2004/09/05 04:41:09; ends 1 2004/09/06 04:41:09; hardware ethernet 00:0d:93:83:8a:8e; uid 01:00:0d:93:83:8a:8e;}

# chkconfig dhcpd on# chkconfig dhcpd on

# service dhcpd start# service dhcpd stop# service dhcpd restart

# service dhcpd start# service dhcpd stop# service dhcpd restart

Page 9: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

Modify Your Routes for DHCP on Linux Server

• Temporary solutionAdd the route to 255.255.255.255 from the command line

If the message 255.255.255.255: Unknown host appears then try adding the following entry to your /etc/hosts file:

Then, try:

• Permanent solution add in /etc/sysconfig/static-routes

If this doesn't work properly try adding the following entry to your /etc/hosts file:

# route add -host dhcp dev eth0# route add -host dhcp dev eth0

# route add -host 255.255.255.255 dev eth0# route add -host 255.255.255.255 dev eth0

255.255.255.255 dhcp255.255.255.255 dhcp

eth0 host 255.255.255.255eth0 host 255.255.255.255

255.255.255.255 dhcp255.255.255.255 dhcp

Page 10: DHCP server & Client Objectives –to learn how to setup dhcp servers Contents –Download and Install The DHCP Package –The /etc/dhcpd.conf File –Upgrading

Summary

• DHCP server is used to deliver IP parameters

• Configuration sit in /etc/dhcpd.conf

• Leases sit in /var/lib/dhcp/dhcpd.leases

• DHCP can deliver boot strap files to diskless

• With options you can deliver many functions

• DHCP server usally run as stand alone server

• Start dhcp server with /etc/init.d/dhcpd start

• Stop dhcp server with /etc/init.d/dhcpd stop

• Reload dhcp server with /etc/init.d/dhcpd restart