Windows server as DHCP not assign IP address

wishwan7321 · ‎04-25-2020

Hi network,

I am building and testing an network for small business and DHCP has troubles giving IP address to workstations between different VLAN. When I put the IP address static in an workstation the computer can get on internet. It seems that there is no messages exchanged between DHCP and client. I hope that someone could help me to fix the problem.

I am using Cisco router 1841 and switch 3560 PoE-8 and Windows server 2019 and here below are the configuration:

Router

interface fastEthernet 0/0

ip address dhcp

ip nat outside

interface fastEthernet 0/1

no ip address

ip nat inside

interface fastEthernet 0/1.10

encapsulation dot1Q 10

ip address 192.168.10.1 255.255.255.0

description VLAN 10 Servers

interface fastEthernet 0/1.20

encapsulation dot1Q 20

ip address 192.168.20.1 255.255.255.0

description VLAN 20 Users

ip access-list standard NAT

permit 192.168.10.0 0.0.0.255

permit 192.168.20.0 0.0.0.255

ip nat inside source list NAT interface FastEthernet0/0 overload

Switch

vlan 10

name Servers

vlan 20

name Users

exit

interface fastEthernet 0/3

switchport mode access

switchport access vlan 20

interface fastEthernet 0/4

switchport mode access

switchport access vlan 10

interface fastEthernet 0/8

switchport trunk encapsulation dot1q

switchport mode trunk

switchport trunk allowed vlan all

Windows Server

IP 192.168.10.10/24

default-gateway 192.168.10.10

dns-server 192.168.10.10

Martin L · ‎04-25-2020

You may still need ip dhcp relay IP command on fastEthernet 0/1.20 despite the fact that it is same router just with sub-interfaces. Anytime there is a router between (separating) DHCP and hosts, you will need install DHCP Relay service (command on router orit could be actual server).

the actual Cisco command is ip helper-address x where x is IP of DHCP server

Regards, ML
**Please Rate All Helpful Responses **

wishwan7321 · ‎04-25-2020

Hi Martin,

Thanks Martin for the small adjust. it helped me indeed but instead getting IP from the server the workstation got an IP from another DHCP outside the scope. I just deleted the DNS forwarder rule so im good to go.

cheers