autoMAC: A Tool for Automating Network Moves, Adds, and Changes Christopher J. Tengi Princeton University

What’s the problem? Over 1500 hosts Over 100 IP subnets/VLANs 672 user switch ports (currently) 388 wall boxes 1072 patch points

1072 Patch Points

Why subnets? Why not a flat network? Broadcast domains User segregation Access Control

How we used to do it host registration requests Manual host database entry Manual patch installation Switch re-configuration

So, what’s wrong with that? Users never get it right the first time Manual host entry is prone to errors Patch panel diving is a pain Did you remember to set the port VLAN? Did you save the switch config?

What we wanted Automation! Less user interaction :-) Better accuracy Static switch configuration

What we did Automate the host database Automate switch port VLAN assignment Keep everyone in the right place

Automating the host database Move to a web-based registration system Use a daemon to process requests Have the daemon rebuild all the database extracts

Automating VLAN assignment No more manual switch configuration Any port, any VLAN, any time Use the host MAC address as the key Registration VLAN for unknown hosts

The nitty-gritty

Tools we used Existing host database FreeRADIUS NetReg

Tools we used - Host DB Originally only for administrators Very little field validation Input through a ‘vi’ -based interface Extracts generated manually with ‘make’

Tools we used - FreeRADIUS Config files generated from Host DB Originally implemented for Cisco APs Our user switches could “speak” RADIUS

Tools we used - NetReg Web-based data input Two to choose from  Carnegie Mellon University  Southwestern University

Integration: Tying it all together

Integration - Host database Web registration form Field validation on the form Automate request processing

Integration - RADIUS server Use MAC address to lookup VLAN Add “tunnel” A/V pairs to accept response Unknown MAC addresses are rejected

Integration - Hardware First, get a vendor to write code for you Why not 802.1X? Known hosts always land on the right VLAN  Locally registered  Mobile IP Unknown hosts land on the registration VLAN

Integration - NetReg Server Listening on the registration VLAN  Answers all DHCP requests  Specifies itself as DNS server/gateway  Answers any HTTP request Requires a CS username/password Presents the host registration form Sends the completed form for processing

Future Enhancements Virus/patch scanning on the registration VLAN Automatic isolation of newly-infected hosts Expand registration VLAN concept to b

Conclusions Automation is a good thing Open Source Software is invaluable Sometimes you can get what you want

Acknowledgements Princeton CS Technical Staff Jon Finke Rob Kolstad

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