?
Solved

Unable to get DHCP lease

Posted on 2010-08-23
11
Medium Priority
?
1,010 Views
Last Modified: 2012-05-10
Hello,

We are having an issue with DHCP leases on our network.  Up until this point we only used static addressing.  At this time we need to be able to pull dynamic lease from one of our DCs.  In this instance our LAN_Client and LAN_DC just are not playing nice.  If you static the client devices IP they are able to communication with everything on the network.

How things move:  Client>DHCP Request>Switch>Firewall>Switch>Server

Our firewall policy is wide open at this time for traffic between the two VLANs.  The switch that is passing data is a PowerConnect 5424.

Detailed movement:  Client>DHCP Request>Switch>VLAN 15>Firewall>VLAN 10>Switch>DHCP response>Client

If we take a client device and connect it directly to VLAN 10 it is able to pull a dynamic address.  

Any thoughts as to what would be causing this?
0
Comment
Question by:jjl505
9 Comments
 
LVL 6

Expert Comment

by:Galtar99
ID: 33506492
Do you have IP helper (assuming you're running cisco switches) or similar statement on your client VLAN's to redirect the DHCP broadcasts to your DHCP server(s)?
http://www.cisco.com/en/US/docs/ios/12_1/iproute/command/reference/1rdipadr.html#wp1018606 
0
 

Author Comment

by:jjl505
ID: 33506574
We are running Dell PowerConnect...
0
 
LVL 4

Expert Comment

by:bhartwell
ID: 33506855
Can your router be configured to allow BOOTP relay? Did you try setting up a dhcp relay agent on the VLAN 15 side of your network? Im guessing that if your trying to communicate across multiple vlans you may need to have the relay agent in place so that the dhcp server knows where those clients reside. This article may be helpful in solving your problem:

http://www.serverwatch.com/tutorials/article.php/2193031/Back-to-Basics-The-DHCP-Relay-Agent.htm

0
Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

 

Author Comment

by:jjl505
ID: 33511512
I will have a loook at the article and get back to you.  Thank you for the prompt response.
0
 
LVL 2

Accepted Solution

by:
pmanno earned 2000 total points
ID: 33524431
DHCP is a broadcast based protocol.  In order for it to work, all machines (client and server) must be in the same broadcast domain.  A firewall/router does not pass broadcast traffic unless it is configured to relay that traffic through in which case it takes the DHCP request and forwards it to one or more servers.

What firewall are you using?  If SonicWall, look at Network -> IP Helper for the configuration of the relay.
0
 
LVL 9

Expert Comment

by:Donboo
ID: 33526250
Looks very much like you problem is the firewall that is not configured to relay the dhcp request.

Check the firewall see if you have configured DHCP relay agent/ IP-helper.

What firewall are you using?
0
 

Author Comment

by:jjl505
ID: 33526516
A Fortinet Fortigate...I will have our Security guy take a look at it.
0
 

Author Comment

by:jjl505
ID: 33627960
It was a firewall issue.  DHCP relaying was not enabled.  I think a thorough beating is in order.
0
 
LVL 2

Expert Comment

by:pmanno
ID: 33627988
Dude, no points!?  I put up DHCP relay...
0

Featured Post

Get expert help—faster!

Need expert help—fast? Use the Help Bell for personalized assistance getting answers to your important questions.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

A Cisco router can be configured as a DHCP Server. There are advantages and disadvantages in making your Cisco router work as DHCP Server. Almost all the features for windows DHCP can be configured on Cisco-based DHCP server. Some of the features me…
This article will show how Aten was able to supply easy management and control for Artear's video walls and wide range display configurations of their newsroom.
Screencast - Getting to Know the Pipeline
Is your OST file inaccessible, Need to transfer OST file from one computer to another? Want to convert OST file to PST? If the answer to any of the above question is yes, then look no further. With the help of Stellar OST to PST Converter, you can e…
Suggested Courses
Course of the Month9 days, 15 hours left to enroll

569 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question