• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 414
  • Last Modified:

incorrect IPs and subnet being handed out but only sometimes

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
huntleyj
Asked:
huntleyj
  • 3
  • 2
1 Solution
 
that1guy15Commented:
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
 
huntleyjAuthor Commented:
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
 
that1guy15Commented:
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
 
huntleyjAuthor Commented:
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
 
that1guy15Commented:
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

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

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

  • 3
  • 2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now