Small Business IP range conflicts

[webbwarrior]

Hi I am a IT worker at a small business of about 10 employees.
We are a performing arts building that does national touring acts about 30 times a year with local community productions in between.

We are only about 6 years old and just got a server based network system last year. Yay! Before that we were just using a linksys routing system and letting the router handle most of the DHCP. When we switched over we just kept the base IP range system that came with the linksys, standard 192. It had not been a problem until a few months ago.

The problem is that we had a group bring in some network gear that was attached to their audio gear and in their tour bus. It is used to link the audio management system to a laptop at the Front of House audio position. When they powered up their system and got everything running our entire network went down no internet, no internal network, nothing. We also use this network to sell online tickets and use it to connect our two office buildings through a Cisco Airbridge 1300 at a distance of about 3/4 of a mile.

When we tried to IP access some of our gear strange password dialog boxes and odd gear started to pop up. When we confronted them they said that the equipment in question was not theirs. Since then the network has not been right and I would like to avoid this in the future from happening again.

I believe that through one of their laptops or some repeater type setting that our two networks got tied together and caused this problem.

I now have a number of machines that wont connect to each other on the network but go on the internet without a problem.

I am wondering if switching to the 172 or other IP range not currently used as a default network on routers will fix the problem. I would like to steer away from the 10, 192, or any others that other companies are using as they build new routers and network with default dhcp ability.

I appreciate any and all feedback on this problem.

 

[dearingkr]

They've obviously added equipemtn to your network that uses the same IP range. In fact, they may have added a device that does DHCP for them.

You've broken one of the golden rules of networking:
NEVER LET ANYONE CONNECT UNKNOWN EQUIPMENT TO YOUR NETWORK!

You have 3 choices:
1. Change your IP scheme
2. Have them change theirs
3. Separate the networks completely

Since it's your network, I would go for #2.

MCSE CCNA CCDA

 

[webbwarrior]

yes i believe that this was the case, the whole thing went to sh*t in a hand bag and there was nothing we could do since they denied the thing existed. Yet the web config page was staring them in the face.

So my question is if switching to the 172 or other IP range not currently used as a default network on routers will fix the problem. I would like to steer away from the 10, 192, or any others that other companies are using as they build new routers and network stuff with default dhcp ability.

Also since this is my first big/small network, I would appreciate any input as to the proper procedures so I don't f#$% it over worse.

Also I don't want to run into any problems with any internet IP things, I had heard from a couple other sources that the 172 range was open but I always like to get a second opinion.

Also I am curious if any one thinks if there would be any lasting effects on the system since after that day the network has never really worked right.

The computers that are actually part of the domain don't have any problems but those that are just hanging out on the system don't seem to really work, Any ideas?

 

[dearingkr]

I would run a network scan, identify the offending devices, and remove them from the network.
It's your network, you need to control it.
Offer to assist them configuring their equipment to play nicely on your network.

If you need one, a popular free scanner is
Angry IP Scanner

If you want to change your IP scheme, you'll also have to re-configure your internet router to make sure it is on the same subnet.

Also note that if they have put a device on your network that is doing DHCP, changing your IP scheme will not do any good. Your computers may still pull their IP info from their DHCP device.

You really need to run a scan on your network to see what's going on.

MCSE CCNA CCDA

 

[webbwarrior]

OK well do you think that having a second dhcp device on the network would leave a lasting effect on the system?

The issue with the people was the fact that they are only in for a day with the tour production that comes in and it is hard to track down everyone is there a way to isolate two devices with the ip scanner?

 

[dearingkr]

Once the devices are removed, there should be no lasting effects.

The scanner will give you some details about what's on the network. From there, you'll have to do some investigating.

For instance, once you indentify a suspect device, you should at least have it's MAC address and/or IP address.
With that info, you'll be able to track it down to what switchport it's connected to.

MCSE CCNA CCDA

 

[Sympology]

If you don't use private address ranges (10, 172,192) you are likely to hit problems.

99.9999% of devices default to the 192 range.

Switching to other private ranges has it benifits, but can have downsides. If for example a device defaults to 192, then it can be difficult to change it (manual IP on PC & local connection)

However even this won't stop other DHCP devices dishing it out.
You may have to looking at firewalling and then directing anything with a 192 address to a black hole.

http://en.wikipedia.org/wiki/Private_network

Only the truly stupid believe they know everything.
Stu.. 2004