Clemson:Network

From Linux 101, The beginner's guide to all things Linux.

1 Introduction
2 Network Registration
3 The Local Network
4 The Internet
5 The Campus Firewall
6 Specific Applications

[edit] Introduction

This article aims to document the quirks of the Clemson University network.

[edit] Network Registration

When you first use a network interface on the campus network you must register its MAC ID. The first time you request a DHCP lease, it checks your MAC address and if you're not in their database, it gives you a restricted 172.* address. This address will not allow you to access most network resources such as the internet and even local network services.

Once you've got this 172.* address, you can visit the network registration page netreg.clemson.edu (in fact, any page you try to visit will take you there). Enter your user ID and password, and then read and accept the service agreement. Now it instructs you to reboot your computer. Visiting netreg.clemson.edu while already authenticated will allow you to see your currently registered MAC addresses as well as add or delete them. If you put in the MAC address of another machine from an already authenticated machine, you will not need to follow the rest of these directions.

Linux users do not need to reboot. You can simply push your network interface down and then obtain a new address with your distribution's DHCP client - probably dhcpcd or dhclient.

# ifconfig eth0 down

# ifconfig eth0 up

# dhclient eth0

Your computer should be given a 130.* address. You are now on the local network.

Note: 172.* addresses are now being given for wireless connections as well.

[edit] The Local Network

There are various services on the Clemson network that you can use once on it.

[edit] The Internet

[edit] The Campus Firewall

Clemson's network is protected from the outside world via its firewall which prevents outside access. The exact specifications of the firewall aren't really important, but it is important to know that certain servers, especially personal ones, are not accessible from outside of Clemson's network. You will have to go through an intermediary system to get onto a number of the campus's workstations or servers, such as the Computer Science network. A way around this is to use the VPN client to gain access to these systems. Specifically related to the Computer Science network, you will first have to ssh into the network's only server available to people off of the Clemson campus, Yoda (aliased to Access). This is done by executing the following command

ssh access.cs.clemson.edu -l <username>

Note: Using ssh to connect to Yoda is best done through the access.cs.clemson.edu address as this is an alias and, in the case that Yoda may be down, it will point to any backup server that has been set up. Going directly to yoda.cs.clemson.edu while it is down will simply fail.

You will be prompted to immediately ssh into another machine that is not Yoda. This is because Yoda is the only link non-VPN link for those off-campus into the Computer Science network and compiling on it is highly discouraged. If you happen to forget, you will receive a fairly insistent letter stating that you really shouldn't do so. Connecting to Yoda from on-campus is not allowed as there is no reason to ssh into it just to ssh into another machine you already have direct access to. If you do attempt to do so, your attempt will be rejected.