Dynamic Host Configuration Protocol (DHCP)

1. DHCP

2. DHCP processing

3. How DHCP Lease Generation Works

DHCP Server2
DHCP Server1
1.
2.
3.
4.
DHCP client
DHCP client broadcasts a DHCPDISCOVER packet
DHCP servers broadcast a DHCPOFFER packet
DHCP client broadcasts a DHCPREQUEST packet
DHCP Server1 broadcasts a DHCPACK packet

4. How DHCP Lease Renewal Works

DHCP Server2
DHCP Server1
1.
2.
3.
4.
DHCP
clients
87.5%
100%
50% of
of
oflease
lease
lease
duration has
expired
DHCP client отправляет DHCPREQUEST packet
DHCP Server1 отправляет DHCPACK packet
Если клиент не обновил ip адрес по истечению 50% времени
лизинга, то повторная попытка будет по истичению 87.5% времени
лизинга.
Если клиент не обновил лизинг на 87.5%, то по истечению 100%
времени лизинга процесс снова начнется с пункта 1.

5. DHCP Relay Agent?

A DHCP relay agent слушает DHCP broadcasts от DHCP clients и
переправляет через роутер к DHCP servers в другие подсети
DHCP
relay
agent
DHCP
broadcast
Unicast
Unicast
DHCP
server
Routers
(non–RFC 1542
compliant)
DHCP clients
DHCP clients
Subnet A
Subnet B

6. DHCP Server Authorization

DHCP authorization registers the DHCP Server service in the
Active Directory domain to support DHCP clients
If DHCP Server2 does not find its IP address on
DHCP
Server2
checks
withipthe
domain
controller
DHCP
client
IPищет
address
еслиlist,
DHCP
Server1
Server1
в support
списках,
the
thereceives
service
does
not адрес
start and
to
obtain
a list DHCP
of иauthorized
servers
from
authorized
Server1 DHCP
сервис
запущен
работает
с DHCP
клиентами
DHCP
clients
Domain
controller
AD DS
DHCP Server1
Authorized
Services DHCP
requests
DHCP Server2
DHCP client
Unauthorized
Does not service
DHCP requests

7. DHCP Scopes?

A DHCP scope область ip адресов
из NA доступных для раздачи
DHCP Server
DHCP scope свойства:
Network Addres
• Время лизинга
• Имя Scope
• Subnet mask
• Network IP address range
• Исключения range
LAN A
LAN B
Scope A
Scope B

8. DHCP Options?

Часто используемые scope options:
• Router
(Default Gateway)
• Primary DNS Server
• Secondary DNS Server
• WINS Servers