Solved

Multiple DHCP servers on the network behavior

Posted on 2009-07-13
7
807 Views
Last Modified: 2012-05-07
Hello,

I have 4 Linksys WRT310N on my network. One is a OpenVPN server and the others OpenVPN clients. 2 of the clients have DHCP enabled. I also have software OpenVPN clients. The problem is some network clients are using remote gateways instead of the local one. For example in Miami the router DHCP server is 192.168.1.1. A client connected to that router is being assigned a IP by the Houston router, 192.168.1.2, when it should be assigned by the Miami router, to which it is connected directly. How to prevent such behavior?

Thank you!
0
Comment
Question by:starusa
  • 3
  • 2
7 Comments
 
LVL 68

Expert Comment

by:Qlemo
ID: 24840104
Have a look whether you have DHCP relay activated on the Linksys clients. As DHCP broadcasts cannot cross a routing connection, the Linksys at each end seems to be do something to allow for it. Or are you running OpenVPN in bridged mode (vs. routing, with own transfer networks)?
0
 
LVL 16

Expert Comment

by:SteveJ
ID: 24866257
I think Qlemo may be onto your problem . . . there's no reason why your local linksys should ignore a DHCP request and pass it to a remote.

Good luck,
SteveJ
0
 

Author Comment

by:starusa
ID: 24904622
Hey guys,
I'm not very into networking. I'm using tap0, so I guess that's bridging. DHCP Relay is the same as DHPC Forwarding? What about changing the router mode from Gateway to Router on the clients?
Thank you.
0
Why You Should Analyze Threat Actor TTPs

After years of analyzing threat actor behavior, it’s become clear that at any given time there are specific tactics, techniques, and procedures (TTPs) that are particularly prevalent. By analyzing and understanding these TTPs, you can dramatically enhance your security program.

 
LVL 68

Expert Comment

by:Qlemo
ID: 24905181
If the OpenVPN clients get IPs of the server network, it is bridged. If OpenVPN uses a separate IP address range, it is routed.

About Linksys router mode - I do not know whether that could influence the DHCP behaviour, but it might.

And DHC relay = DHCP forwarding.
0
 

Author Comment

by:starusa
ID: 24905452
Well, in that case I'm using bridged mode. The router which is the vpn server is configured as 192.168.3.1 and the clients have the same 192.168.3.x. Also, DHCP forwarding is not enabled for any router.
0
 
LVL 68

Accepted Solution

by:
Qlemo earned 500 total points
ID: 24924142
I'm guessing only. I assume the DHCP requests are forwarded using OpenVPN because of the bridge mode. But that should not be the case, as the routers themselves are acting as DHCP servers.

Well, as a workaround you could use DHCP ClassID, set up on client by
ipconfig /setclassid "Local Area Connection" MyNewClassId
, and name the Scope of each site's DHCP server accordingly. A client without a ClassID is getting an arbitrary DHCP address, though.
This requires you use DHCP servers capable of Scopes / ClassIDs, of course ...

0

Featured Post

Better Security Awareness With Threat Intelligence

See how one of the leading financial services organizations uses Recorded Future as part of a holistic threat intelligence program to promote security awareness and proactively and efficiently identify threats.

Join & Write a Comment

Suggested Solutions

Quality of Service (QoS) options are nearly endless when it comes to networks today. This article is merely one example of how it can be handled in a hub-n-spoke design using a 3-tier configuration.
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…
Viewers will learn how to connect to a wireless network using the network security key. They will also learn how to access the IP address and DNS server for connections that must be done manually. After setting up a router, find the network security…
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…

747 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

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now