DHCP Dynamic host configuration protocol

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DHCP (Dynamic host configuration protocol)
DHCP Server - computer running the dhcp service
. . .
DHCP Clients hosts depending on the dhcp service
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DHCP
What do we mean by dynamic?
Would a DHCP client that received exactly the
same settings each time it turned on qualify as
using dhcp?
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DHCP
What do we mean by configuration?
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DHCP
Why use DHCP?
Any modification in network configuration can be
made by
New machines on a LAN can be integrated by
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DHCP - server
1. As root, make sure /etc/sysconfig/network/ifcf
g-eth0 specifies a static IP address (dont want
dhcp server to act as a dhcp client)
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DHCP - server
The d is for daemon or server
2. As root, in /etc create a file called
dhcpd.conf
Suse Linux needs this
dhcpd.confddns-update-style noneoption
domain-name "CIS373.net"default-lease-time
1800max-lease-time 7200subnet 192.168.10.0
netmask 255.255.255.0 range 192.168.10.150
192.168.10.200host Computer4 hardware
ethernet 000347F6CF0A fixed-address
192.168.10.222
Other options would be?
Default lease time is 30 minutes max is two
hours.
These are the IP addresses the server is leasing
What is this?
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DHCP - server
3. Remove all traces of any previous dhcp
services
in /var/lib/dhcp, remove dhcpd.leases and
dhcpd.leases rm dhcpd.leases rm dhcpd.leases
4. Create an empty dhcpd.leases file
Still in /var/lib/dhcp touch dhcpd.leases
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DHCP dhcpd.leases example pg 1 of 2
All times in this file are in UTC (GMT), not
your local timezone. This is not a bug, so
please don't ask about it. There is no portable
way to store leases in the local timezone, so
please don't request this as a feature. If
this is inconvenient or confusing to you, we
sincerely apologize. Seriously, though -
don't ask. The format of this file is
documented in the dhcpd.leases(5) manual page.
This lease file was written by isc-dhcp-V3.0.1rc6

What is UTC? http//setiathome.ssl.berkeley.ed
u/utc.html http//en.wikipedia.org/wiki/UTC
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DHCP dhcpd.leases example pg 2 of 2
lease 192.168.10.200 starts 2 2004/11/23
171047 ends 2 2004/11/23 191047 binding
state active next binding state free
hardware ethernet 000347f6c580 uid
"\001\000\003G\366\305\200" client-hostname
"itl06i" lease 192.168.10.199 starts 2
2004/11/23 171121 ends 2 2004/11/23
191121 binding state active next binding
state free hardware ethernet
000347f6dacb uid "\001\000\003G\366\332\31
3" client-hostname "itl07i"
Why is this dhcp server handing out these
particular IP addresses?
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DHCP - server
5. Start the service
In /etc/init.d, enter this command ./dhcpd start
Reminder what does ./ mean???
Once you have removed all syntax errors from
dhcpd.conf, you will see
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DHCP - server
6. Confirm the service
As root, issue this command ps ef grep dhcp
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DHCP - client
1. Configure client to use dhcp
In /etc/sysconfig/network, be sure ifcfg-eth0
sets the interface up to use dhcp
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DHCP - client
2. Remove all traces of previous dhcp leases
In /var/lib/dhcpcd, remove dhcpcd-eth0.info and
dhcpcd-eth0.cache But dont remove dhcpcd-eth0.
timestamp
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DHCP - client
dhcpcd-eth0.info
IPADDR192.168.10.200NETMASK255.255.255.0NETWOR
K192.168.10.0BROADCAST192.168.10.255DOMAINCI
S373.netDNS192.168.10.1DHCPSID192.168.10.1DHC
PGIADDR0.0.0.0DHCPSIADDR192.168.10.1DHCPCHADDR
000347F6C580DHCPSHADDR000347F6DB49DH
CPSNAMELEASETIME7200RENEWALTIME3600REBINDTIM
E6300INTERFACEeth0CLASSID"Linux
2.4.18-64GB-SMP i686"CLIENTID000347F6C580
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DHCP - client
3. Now when the computer boots, it will look to
find a dhcp server
You can simulate the boot process as far as the
dhcp client is concerned by these commands In
/etc/init.d ./network stop ./network start
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DHCP - client