Hot Downloads



The forum is in read only mode.
Welcome, Guest
Username: Password: Remember me
  • Page:
  • 1

TOPIC: Some Doubts about DHCP?

Some Doubts about DHCP? 13 years 10 months ago #8189

Hi Friends
I was asked this question at an interview. THe person asked if he has 2000 computers in a company. There are 9 DHCP severs to handle the ip address allotment. The company adds more 50 computers in a department . How will the new computers added know out of 9 DHCP servers to which DHCP server they should contact for ip address ?
I got not give the answer of this question. It would be really nice if someone could help me with this question :)

I could be wrong but..... 13 years 10 months ago #8190


Not a nice question!
For me this question cannot really be answered fully without knowing the architecture of the network.

I would assume that the 2000 machines are over several logical sites which are connected via switches / routers. The switch / router for each logical site would need to be configured as a DHCP relay for it's site.

Simple example:

SWITCH A is configured with a DHCP relay address of is the address of DHCP SERVER 1

SWITCH A recieves a DHCP request from PC "Z"

SWITCH A forwards the DHCP request to The packet has the IP address of SWITCH A as the source address

DHCP SERVER 1 recieves the request and sends a reply to SWITCH A with IP address to be assigned

SWITCH A forwards the reply to PC "Z"

So in answer to the question each of the 50 pcs would use the DHCP server that it's switch/router is configured to use.

I hope this make sense and helps. Maybe someone with a bit more experiance then me can check!


Patience - the last reserve of the any engineer

DHCP 13 years 10 months ago #8192

Since they didn't give you any detailed information on the design of the network, I would just have given them the simple answer:
When a workstation is added to the network it will send a DHCP broadcast which effectively says "hello, I'm a DHCP client, is there a DHCP server out there that would like to give me an IP address?" One or more DHCP servers may respond to this. The workstation will act on the first response that comes in, which is most likely to be from the nearest (in network terms) DHCP server. So unless they have done something more sophisticated it will most likely be the nearest, most local server to the new clients that will allocate the addresses.
If they wanted more, they would then have to give you more info to get it

Re: Some Doubts about DHCP? 13 years 10 months ago #8197

What is given is there are 2000 PC already in place and with 9 DHCP server. Logically, I would think these 9 DHCP servers are serving 9 VLAN. These 9 VLAN could be 9 separate departments of a company. If the switch is configurated correctly, with the correct VLAN, the PC should be able to get an IP from the correct DHCP server.
  • Page:
  • 1
Time to create page: 0.136 seconds


Cisco Routers

  • SSL WebVPN
  • Securing Routers
  • Policy Based Routing
  • Router on-a-Stick

VPN Security

  • Understand DMVPN
  • GRE/IPSec Configuration
  • Site-to-Site IPSec VPN
  • IPSec Modes

Cisco Help

  • VPN Client Windows 8
  • VPN Client Windows 7
  • CCP Display Problem
  • Cisco Support App.

Windows 2012

  • New Features
  • Licensing
  • Hyper-V / VDI
  • Install Hyper-V


  • File Permissions
  • Webmin
  • Groups - Users
  • Samba Setup