Solved

ip dhcp relay

Posted on 2013-06-18
8
264 Views
Last Modified: 2013-10-31
This is my setup:
DHCP server<-->core switch (L3) <--> sw1 (L2) <-->sw2 (L2) <---> PC1

PC1 is using dhcp. But it could not get the DHCP from the server. If I configure it with a static IP address, everything works. Somebody suggested enabling dhcp relay on sw1. But I disagree because from my understanding, the dhcp relay is used to forward DHCP traffic between 2 different subnets. Furthermore, I don't think the layer 2 switch can do dhcp relay. Any thoughts would be greatly appreciated. Thx
0
Comment
Question by:leblanc
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
8 Comments
 
LVL 9

Accepted Solution

by:
gt2847c earned 250 total points
ID: 39257066
DHCP relay would be enabled on the L3 switch.  The VLAN interface routing for the PC would have to forward it as it has knowledge of the origination subnet...
0
 
LVL 1

Expert Comment

by:JoPeLo
ID: 39257162
Looking at your layout, I believe the DHCP server is in a different subnet (VLAN?) of PC1. If so, you should configure the DHCP relay on your core switch L3. In cisco gear, the DHCP relay agent is configured using the ip helper-address interface command.
If the DHCP server is in the same VLAN of your PC1, and supposing you are not using PVLANs, you should look for trunk misconfiguration in all trunk configurations in sw1, sw2 and core switch (is that VLAN allowed in all trunk interfaces?) and/or if that VLAN exists in all switches.

Hope it helps.

jopelo
0
 
LVL 1

Author Comment

by:leblanc
ID: 39257310
I am not using PVLAN. I will check the trunk configuration.
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 16

Assisted Solution

by:vivigatt
vivigatt earned 250 total points
ID: 39259948
Are the DHCP server and the client(s) in the same subnet?
If so, you need a DHCP relay (ip helper in Cisco world).
If not, this is something else...
0
 
LVL 1

Author Comment

by:leblanc
ID: 39262584
Yes dhcp server and the client are in the same subnet and same vlan.
0
 
LVL 16

Expert Comment

by:vivigatt
ID: 39262657
OK, so you don't need DHCP relay.
You must make sure that broadcast packets are handled correctly from end-to-end
0
 
LVL 1

Assisted Solution

by:leblanc
leblanc earned 0 total points
ID: 39266210
I found out that the vlan where the dhcp server is  connected to was not configured.
0
 
LVL 1

Author Closing Comment

by:leblanc
ID: 39613558
i found out that the dhcp sever was no configured correctly
0

Featured Post

What, When and Where - Security Threats from Q1

Join Corey Nachreiner, CTO, and Marc Laliberte, Information Security Threat Analyst, on July 26th as they explore their key findings from the first quarter of 2017.

Question has a verified solution.

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

When it comes to security, there are always trade-offs between security and convenience/ease of administration. This article examines some of the main pros and cons of using key authentication vs password authentication for hosting an SFTP server.
This article is in regards to the Cisco QSFP-4SFP10G-CU1M cables, which are designed to uplink/downlink 40GB ports to 10GB SFP ports. I recently experienced this and found very little configuration documentation on how these are supposed to be confi…
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're looking for how to monitor bandwidth using netflow or packet s…
There's a multitude of different network monitoring solutions out there, and you're probably wondering what makes NetCrunch so special. It's completely agentless, but does let you create an agent, if you desire. It offers powerful scalability …
Suggested Courses

632 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