Securing the wired network with 802.1X

This post covers an innovation project I did to secure the wired network at a shared conf center with 802.1X.

Every few months we had to disable the wired network in order to prevent non-employees from being able to get online. This was not scalable, was prone to human error, and scheduling confusion. I planned to automate the process by enabling 802.1X aka dot1q on the switches using our Windows AD via Cisco ACS.

Any Domain joined devices that plugged in would get access to our corp VLAN, and unknown devices would go into a dead VLAN. Long term I planned to enable a wired guest VLAN and had it labbed out for non local switched wifi where the guest VLAN exists on the switch you’re connected to but didn’t around to labbing local switching using CAPWAP tunnels.

Wired Guest Access using Cisco WLAN Controllers Configuration Example:

Phones would Continue reading...

NTP redesign

This post is about a bug that affected NTP (Network Time Protocol) and our redesign of the environment bypass the issue.


In this environment the core Cisco 7604 IOS routers were the NTP stratum 2 servers (x.x.x.123 because fun with port numbers). The IP was an HSRP standby IP. There were several downstream Linux NTP servers and Window Domain Controllers serving NTP to Windows clients. As unsupported Linux servers died their IP’s were just added to servers that were still alive. Eventually this got messy.

After the 7604 routers were replaced with a pair of ASR1006X we ran into some interesting issues. Windows users we no longer able to log. Turns out the Domain Controllers were falling out of sync. My Infoblox DDI servers also showed stale time. Users were eventually able to log into the Domain either before or after the Windows team changed their NTP config. The Continue reading...