Welcome to the third part of our special feature on setting up a world-class LAN Party. In Part 1, I described how to organize a smooth-running LAN party and get it powered properly. In Part 2, I described selecting and setting up the LAN's switching gear and provided some tips on selecting and making cables.
In this installment, you will learn a few of the techniques I use when troubleshooting problems that arise on a LAN Party network. Most of these techniques require use of managed Ethernet switches. While each managed switch has entirely different syntax and ways of accomplishing these tasks, most should be able to support these procedures. The examples are based on the HP Procurve switches that I use and recommend.
A managed switch at the core is a must
Core Switch Setup Tips
Before I get into troubleshooting, let me first offer some tips for setting up your core switch for the best LAN Party performance.
Disable Broadcast Storm Detection
This sounds like a devastating thing to do, but in a LAN Party environment, it's essential. Windows-based PCs that implement File & Printer Sharing (on by default on most installations) build and maintain the Network Neighborhood computers and workgroups lists through broadcasts using NetBIOS.
Once the number of systems on the network passes a certain point, the number of NetBIOS broadcasts will appear to your core switch as uncontrolled bursts of traffic that must be stopped. So the switch will begin blocking broadcasts. Even if you don't care about supporting Windows file sharing, blocking broadcasts will also stop game clients from locating game servers on the LAN because this mechanism also uses broadcasts.
On the HP Procurve 2824 switch, issuing the following command at a CLI prompt via Telnet or ssh will disable broadcast storm detection:
hp2824# config terminal hp2824(config)# no fault-finder broadcast-storm hp2824(config)# exit
Disable Flow Control for uplink ports
Flow Control or IEEE 802.3x is a standard protocol that switches and PCs can use to provide for consistent, steady speed at the expense of top-end performance. I recommend disabling flow control because an uplink port carries traffic for as many as 24 users in our configuration. One user's packets shouldn't be throttled or slowed down at the expense of other users on the same table switch.
If you decide against disabling flow control, or forget to make sure it's disabled, users connected to that uplink might experience elevated ping times (increased latency or lag) as the load on the port increases and not just when it's saturated! On our Procurve 2824 switch, flow control disabled is the default configuration for all ports, so we didn't have to do anything. But in case you accidentally enable flow control, here's how you would disable it again:
hp2824# config terminal hp2824(config)# no interface 1 flow-control hp2824(config)# no interface 2 flow-control hp2824(config)# exit
Your table (if you're using managed switches) and server row switches should have flow control enabled or set to Automatic for all ports. On the Procurve 2626, it's enabled as follows:
hp2824# config terminal hp2824(config)# interface 1 flow-control hp2824(config)# interface 2 flow-control hp2824(config)# exit
Label your ports
Managed switches maintain a "label" for each port of the switch. These labels are useful for SNMP management software such as traffic graphing and reporting. Once you have your LAN up and running, take the 5 or 6 minutes to label your ports. The HP Procurve 2824 switch uses the following command to label the various ports:
hp2824# config terminal hp2824(config)# interface 1 name "Table 1" hp2824(config)# interface 2 name "Table 2" hp2824(config)# exit