Solved

ip dhcp relay

Posted on 2013-06-18
8
260 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
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
PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

 
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

Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Converting TV to Network (Muli-User) Web front. 8 63
Dns issues 4 35
Non-jumbo host to jumbo enabled switch: Will it work? 3 17
Cisco  3750E switches 1 13
This is an article about my experiences with remote access to my clients (so that I may serve them) and eventually to my home office system via Radmin Remote Control. I have been using remote access for over 10 years and have been improving my metho…
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.
Internet Business Fax to Email Made Easy - With  eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, f…
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…

770 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