DHCP and Wireless

[Alberto Diaz_1]

Hello,

I have a problem with wireless devices. I have configured a wireless infrastructure with 350 Access Points (Aironet 1100 and aironet 1200), and 2 CiscoSecure ACS appliances.

Clients authenticate via MAC Address, but sometimes they cannot get an IP Address from DHCP Server, specially when a lot of people is trying to authenticate against RADIUS Server.

I would appreciate any help.

Thank you,

Alberto Dí

[Alexander Chuzhoy]

If there is a problem when a lot of people trying to connect-maybe all addresses from the pool are occupied at the time. Check that.

[Alberto Diaz_1]

Thanks, but it is not the problem

Bye

[Ernest Ford]

How many users do you have trying to authenticate at the same time?

Have you considered network congestion or simply an overloaded RADIUS server?

350 access points is a very large number - what is the geographical area that these access points are located over? How are they connected together? Are there routers and WAN links in between the access points and the RADIUS server?

I'm thinking that your problem relates more to your network architecture than the wireless itself - unless that 350 is a reference to the Cisco Aironet 350 access point and not a quantity.

[Rune J. Winje]

Sounds like a congestion/traffic problem.

The number of DHCP servers (or more conveniently number of DHCP proxies) and their closeness to the clients in the wireless/network infrastructure is critical.

Also be aware that the authentication by MAC address is easily circumvented by hackers.
-> macchanger is a standard "security" tool in Linux
-> several Knoppix distributions also include this tool as well as wireless sniffers, password crackers etc (Knoppix is Linux on a bootable CD which can boot off just about any PC/portable)

Do require WPA and/or VPN authentication of your wireless users to have a reasonable security level.



Cheers,
Rune