College ethernet switch problems

It is very easy to block MAC address prefixes in a DHCP server. More than likely, your sys admins of the DHCP servers have found relevant MAC address prefixes for the popular broadband routers and denied them from obtaining IP addresses.

Do not be afraid to ask questions, and be honest. Give your helpdesk a call, and request to talk with someone in networking. Do not assume that you can get fancy with some setup and skirt by under the radar. If your network admins are smart, then can detect all kinds of anomalies like downstream switches/hubs, broadband routers, wireless APs, etc. More than likely, you are paying a port fee, which may be built in to your room rate. That port fee is probably for one port, and the network in your building may only be designed to support one host or two hosts per room. Call and ask.

-mike

snipped-for-privacy@yahoo.com wrote:

Thanks Mike, I called them and they ran through everything they could and we think its a broken switch. It shows a link and activity, but wont go full duplex, and the computers connected all say limited or no activity. So now I go and buy a switch. One thing that has been bothering me is why wouldnt they want routers on the network? What detrement does that have on the network? Is it just because you disguise your IP? Thanks!

(snip)

Not very convincing. First, if the router is used by just one person, then you know who it is. They should use managed switches so they can track things down to the port, independent of MAC address, and supply enough ethernet ports per room so that each occupant has a port that they are responsible for.

This is more convincing, though the rule should then be no wireless routers, or at least no wireless routers without encryption turned on.

Note that both hosts and routers can easily change their MAC address, so identifying hosts or routers based on that doesn't make much sense.

Many routers are just linux machines inside. I have heard that some linksys routers can have linux downloaded into, and run just like any other linux host.

Much worse than routers is most versions of windows with sharing enabled, or with older versions even with it disabled.

-- glen

It could be a legal thing. College networks generally have LOTS of p2p traffic. If a dorm room is masked by a broadband router, it's possible that either dorm-inhabitant could have innitated an illegal download from the routers "outside" address, not to mention any wireless clients that could have latched on to the thing (if it's a wireless router).

You don't know that only one person is behind the router. We did this when I was at school - we had to pay per activated port, so my roommate, the 2 neighbors and I pitched in on the per-semester bill and split the cost of the router and we shared one connection.

Students are now bringing desktops, laptops, Playstations, XBoxes, blah, blah... One ethernet port, per student, is unrealistic in many cases. We are not concerned about billing because a student pays for the port whether they use it or not because it is built into their room rate. We have told students that NAT routers are okay, but NAT routers with the wireless option are not okay. We require MAC address registration, so even routers have to be registered devices. Registering devices like Playstations and XBoxes can be problematic, so we encourage students to use NAT routers for connectivity to those devices.

It is too complicated to try and expla>

Since it was once working, I can only assume some sort of config change. Since you didn't do it, it must have been upstream.

You don't really disguise your IP, but you could shovel more traffic through a router. For some reason (paranoia perhaps justified about wireless) they really don't want routers. You really should comply. It is their network.

Well, detecting and blocking routers isn't exactly easy and the skule's netadmins may not have the skills. But forcing all ports to 100 is simpler and will block out many SOHO routers because their WAN uplink ports are only 10baseT.

-- Robert

(snip)

The linksys WRT54G has a 10/100 half/full duplex WAN port. It can also run linux such that it should be technically a computer and not a router. (It may be that they run linux out of the box, but there are also versions that one can download to them.)

Though a 10/100 switch should be about $5 these days used or on sale new. Not more than $10, anyway.

Find one on eBay if your store doesn't have one.

-- glen