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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?

that1guy15

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

huntleyj

ASKER

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.

that1guy15

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.

huntleyj

ASKER

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.

ASKER CERTIFIED SOLUTION

that1guy15

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