Today is one of those crazy days where my network can not even seem to sustain a voip call. Frankly this really annoys me so I decided to debug my network. Recently I upgraded my home office to a business class cable modem with 5/22Mbps service. Simultaneously with that (yes, unadvised in any network deployment) I put in a high performance Gbps Switch and a professional Firewall. I’m leaving out the manufacturer names because I don’t want them to tell me their appliance is fine it is just misconfigured – they were configured by professional IT network engineers.
My network prior to debugging looked like this:
From my desk connected to the Dlink DIR-655 my internet performance was a pitiful 3Mbps but I know this is not the Dlink’s fault. The Switch and the Firewall are in my basement so I went down and plugged directly into the switch. To my amazement I was still only getting 3Mbps. Moving up the chain I plugged straight into the Firewall but I was still only getting ~3Mbps.
Aha… I thought here is the problem. Must be a configuration issue right? But the more I searched I could not find anything. Now I will admit I’m not a Network Engineer but I’m not ignorant either. I called up the NY office (which has the same Firewall but T1’s) and had them run a test. They also achieved ~3Mbps. Hum… we have the same switches and firewall….
So now I plug directly into the back of the cable modem which has a 4-port hub and ran speed tests. I got a whopping 40Mbps. Yahoo! (oh wait, I use Google – GooHoo!).
So then I think ok, must be the Firewall. The cable modem can do DHCP so I configure it to match my network’s IP address and then plug straight into the switch. Dang… no luck. It won’t even show a link light. I happened to notice during my direct connects to the cable modem hub that they only had 100Mbps links. For some reason the switch wouldn’t auto negotiate this link. So, ok, put the network back, log into the switch, set the port to 100Mbps full duplex, disconnect the Firewall and try again.
I then plug my laptop directly into the switch (yes, I disabled wireless) and to my utter amazement I was still only getting 8-10Mbps running internet speed tests. This is completely unacceptable because the switch has a rating of 20Gpbs+ aggregate performance. I have almost nothing connected to this switch (as you can see from the above). So now I’m completely annoyed. The difference between a switch and a hub is supposed to be that a switch makes a direct connection between ethernet ports so that two devices can communicate without retries and collisions. A hub on the other hand rebroadcasts on every port all packets that are received and thus there can be many collisions. To make things more embarrassing, my switch is supposed to be able to do some Layer 3 routing.
So, ok, I’m at a loss for words. It turns out (see my network diagram) that I have only 3 devices in the switch (4 wires – 3 devices) so I think what the heck, let’s plug them all into the cable modem hub. After doing that I measure the internet performance at the cable modem again and I’m still pulling 40Mbps. Goohoo!
So leaving that network configuration and just removing the Firewall and Switch (but using the cable modem’s firewall and hub), from my 3rd floor connected over an 11n draft link, I now get the following:
Thus this is a case when a hub is better than a switch!
Time for a beer.
