Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

incorrect IPs and subnet being handed out but only sometimes

Posted on 2008-10-16
5
Medium Priority
?
407 Views
Last Modified: 2012-05-05
This is a wierd one and keep in mind that it only happens on occasion. The setup is for a hotel and conference area.

Basic Setup:
Cisco 1841 router setup up as DHCP server to hand out IPs between 10.0.0.40 -254 (255.255.255.0 Subnet)
From Router ---> Dell 3048 switches to split to different rooms and Cisco 1121 APs.
The router, switches and AP's all have static IPs set in the 10.0.0.1-39 range

I have triple checked that all the APs are NOT setup as a DHCP servers and their "role in the network" are set as Access Points.
 
The issue is sometimes when guests (or even I) connect to an AP they are being assigned an IP of 10.0.0.19 (or ony one of the IPs below the routers DHCP scope) and a subnet of 255.255.255.224 !?!

Any ideas on where to begin troubleshooting this?
0
Comment
Question by:huntleyj
[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
  • 3
  • 2
5 Comments
 
LVL 23

Expert Comment

by:that1guy15
ID: 22732415
Someone is connecting a router/access point to your network that has DHCP enabled. I would assume since this is a hotel a guest has a small home router that is configured with DHCP and when they connect it to your network it starts passing out IPs. They are most likley using it to get wireless access to a computer or access for multiple computers through one connection
0
 
LVL 3

Author Comment

by:huntleyj
ID: 22732516
Possible. Next few times it happens I'll look at the DCHP bindings on the router and record the MAC addresses and look for a common MAC Address. That's if it's the same guest.
0
 
LVL 23

Expert Comment

by:that1guy15
ID: 22732583
If it is always the same block of IPs then it could be an employee or a guest that stays frequently. Even though the 10.0.0.0 range is very common you would usually see the assigned ips all over the board.
0
 
LVL 3

Author Comment

by:huntleyj
ID: 22732636
What I might do is change the whole IP scope to something less common, say 10.113.0.x . A bit of a pain but if it fixes it it will be well worth it.
0
 
LVL 23

Accepted Solution

by:
that1guy15 earned 2000 total points
ID: 22732842
You can do that but it will not stop rouge DHCP servers from passing out IPs. But you will know when someone gets the wrong ip because they will not be able to communicate with anything.
0

Featured Post

Looking for the Wi-Fi vendor that's right for you?

We know how difficult it can be to evaluate Wi-Fi vendors, so we created this helpful Wi-Fi Buyer's Guide to help you find the Wi-Fi vendor that's right for your business! Download the guide and get started on our checklist today!

Question has a verified solution.

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

In the hope of saving someone else's sanity... About a year ago we bought a Cisco 1921 router with two ADSL/VDSL EHWIC cards to load balance local network traffic over the two broadband lines we have, but we couldn't get the routing to work consi…
The Cisco RV042 router is a popular small network interfacing device that is often used as an internet gateway. Network administrators need to get at the management interface to make settings, change passwords, etc. This access is generally done usi…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
Suggested Courses

609 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