Subnet or not?

[iolair]

Okay, this is a design question. I have two buildings that are 800' apart. Currently, they're connected by Cat3 telephone wire in the ground and repeaters.

1. Should I put the two buildings on seperate subnets?
2. What applications require broadcasts? (if I use a router,
will some things not function because of broadcasting)
3. Would wireless be a better solution for these buildings?
4. Fiber Optic is not an option, would multiple Cat3 links
be better than wireless?

Iolair MacWalter
Network Engineer

 

[PScottC]

1. Depends on a lot of factors:
A. How many machines are on each side of the connection?
B. Where is the primary data center in relationship to this connection?
C. How much data do you expect to pass across the link?
2. If you have DNS in place, most applications can survive without broadcast (except DHCP, where you will require a proxy or helper application). A number of applications rely on Multicast (like Apple's Bonjour protocol), so you will have to take it into consideration.
3. Outdoor wireless requires special equipment and professional installation. Do you have the budget for that? It is also subject to interferance. Do you have clear line of sight between the buildings with no possibility of tree growth or additional building construction in the path?
4. On a Cat3 link, I think the most you can expect is 10Mb/s. I don't know if link aggregation (etherchannel) permits repeaters in the link. You could get up to 54Mb/s on a wireless link, but again it is subject to degraded signal.


PSC
[—] CCNP[sub][blue]x3[/blue][/sub] (Security/R&S/Wireless) [•] MCITP: Enterprise Admin [•] MCSE [—]

Governments and corporations need people like you and me. We are samurai. The keyboard cowboys. And all those other people out there who have no idea what's going on are the cattle. Mooo! --from "Hackers

 

[stubnski]

I'll echo what PScottC said and toss in a few more things.

==> 1. Should I put the two buildings on seperate subnets?
Yes. Networks will only grow (hopefully) so organize it right away.

==>2. What applications require broadcasts?

Only you know what applications you have and will have to research that issue but most will not have any issue. Maybe a L3 switch would be a better way to connect them if you are concerned about broadcasts

==>3. Would wireless be a better solution for these buildings?

What PScottC said

==>4. Fiber Optic is not an option, would multiple Cat3 links be better than wireless?

You can get up to 100mb from wireless, probably higher but I haven't checked around. Of course the higher the bandwidth the more expensive it is.


Stubnski

 

[iolair]

The data center is in the admin building, and there are 25 devices (PC's, Servers, printers) in that building. The MPLS router to the internet is also in the admin building. This building houses the Registrar and Business offices, along with the Executive offices.

In the instructional building, there are 53 devices. Mostly PC's and printers, but I could add a DHCP server there. This building houses instructors who do a lot of online research and preparation of class materials.

Yes, I have a clear line of sight, with no trees possible. There is a lot of pavement between the buildings, which makes running new cable and/or fiber a problem - management is not willing to resurface or dig up parking lots.

I just wasn't sure if Windows needed broadcasts to find the server, printers, etc. Or if Office uses a broadcast in any way to save files to network shares.

As far as data goes, I'm looking into that right now. I've got Wireshark and some other monitoring software running to see how much data flows. The repeaters I have now say they can run up to 50Mbps. I get complaints sporadically about the speed of the connection, so I'm assuming the traffic is bursty, not consistently so.

Thanks for the answers. Good answers, too.

Iolair MacWalter
Network Engineer

 

[vipergg]

also if using copper between buildings you could run into ground potential issues could be the cause of some your slowness specially if its only cat 3 wire . It is generally advised to use fiber between buildings and i know that doesn't seem to be an option so maybe wireless might be your answer though that can be susceptable in weather extremes also .

 

[intelwizrd]

Are both buildings serviced by a telco? Could get a second internet connection and set up a site-to-site vpn, or get a point-to-point link, price could be an issue for you though.

Is the existing line run through conduit? If it is big enough and straight enough you could pull additional lines through it. If the conduit is relatively sealed and big enough, you can tie a pull string to a plastic grocery bag and put a vacuum (like a shop vac) on the other end.

I have had some experience with outdoor point-to-point wireless. Had it running between two buildings (maybe a 100' apart). It had its issues though. That was also about 8 years ago and I am sure the tech has improved quite a bit since then. Probably didn't help that there were a lot of transmitting devices on the roof either.

good luck to you, not an easy task.

 

[PScottC]

I was thinking along similar lines with intelwizrd... If you have existing Cat 3 cable and a repeater in the middle somewhere, that means that you have existing conduit (with pull boxes) between the buildings. Why can't you use that existing conduit to run your fiber?

PSC
[—] CCNP[sub][blue]x3[/blue][/sub] (Security/R&S/Wireless) [•] MCITP: Enterprise Admin [•] MCSE [—]

Governments and corporations need people like you and me. We are samurai. The keyboard cowboys. And all those other people out there who have no idea what's going on are the cattle. Mooo! --from "Hackers

 

[iolair]

Alas, the orignal Cat3 is in the ground, not in conduit. The orignal buildings were built in 1974. It has been backhoed a couple of times. I wish there were conduit, because then I would have fiber pulled for sure.

I have outdoor wireless for a couple of other buildings, and it seems to work fine, but it's only for a couple of users who are about 1/2 mile away. But you're right, it's unreliable - the least little bit of weather seems to take it off line and both antenna/radios have to be rebooted.

The way it works now is there is one repeater in the admin building connected to a switch, then to the Cat3 in the ground, and another repeater in the other building connected the same way. Via 66 blocks in each building.

To answer the question about the telco, no, both buildings are on campus, but only the admin building has the actual demarc and lines to the street.

Iolair MacWalter
Network Engineer

 

[PScottC]

If you have budget, you might look into a microwave dish installation. I'm not talking about 802.11a/b/g/n wireless, I'm talking telco grade wireless. A good installation should have a very solid connection. I have a client with an Internet connection of this type. He has reported solid connection even during rainy weather.

PSC
[—] CCNP[sub][blue]x3[/blue][/sub] (Security/R&S/Wireless) [•] MCITP: Enterprise Admin [•] MCSE [—]

Governments and corporations need people like you and me. We are samurai. The keyboard cowboys. And all those other people out there who have no idea what's going on are the cattle. Mooo! --from "Hackers

 

[intelwizrd]

I wonder if you have enough of a budget and space to get a directional boring machine and put some conduit in between the buildings. could be a solution for you to get some fiber installed. Only disturbs the surface where it does in and comes out. I don't know how much they cost but I drove by one this morning on my way to work and thought about this. It took me a while to come up with the correct term and search for it. Looks like there are some contractors companies that will come in and do it for anything from residential to comm to govt. Worth a phone call at least. Just be sure to put in a big enough conduit for multiple wire/fiber runs. You can sell them on doing this in expectation of upgrading the phone system and network infrastructure, etc. Good luck with that

 

[iolair]

@PScottC - I've looked at those, there is even a wireless "optical" device that Sony makes that is supposed to be really, really fast. But, really, really expensive.

@intelwizrd - yes, I have looked at the boring, and if I can work out the budget, we'll do that. I know they're limited as to how many feet they can go, and that might be an issue. Like I said, a lot of parking lot between here and there, including a road that is heavily traveled by personnel here. Do you think a 4" conduit is big enough?

Thanks again for everyone's help, I really appreciate it.

Iolair MacWalter
Network Engineer

 

[intelwizrd]

From a sizing perspective, that depends on how many wires and what kind you want to pull through it. You could always go to a hardware store and get some different sizes of PVC or even just the couplings and sit there at your desk with the different wires to see what kind of space you have left. Or even take a piece of plywood or some other stiff material and cut a hole in it. Don't forget to take into account if you are going to pull the fiber or other cables with terminations or without as that can add some bulk as it is being pulled that wont be there when it is just the cable. Obviously you want to leave room for growth and you don't want to oversize since large conduit can be expensive.

 

[iolair]

Thanks. Makes good sense. I'll go get some PVC today and test it out.

Iolair MacWalter
Network Engineer

 

[baddos]

Do you have an existing ethernet connection to this building using that Cat3 wire? I would think a direct bury Cat3 cable going 800' without 2 repeaters in the middle somewhere would be difficult to operate to say the least. Even 10mb half duplex shouldn't be attempted past 312 feet.
Read

http://en.wikipedia.org/wiki/10BASE-T

for cabling specs if you aren't familiar with them.

If you do have an ethernet connection between those buildings now, are they terminated into managed switches where you can look at the port statistics on them? I would be curious to see what errors you are receiving.

If you continue using that Cat3 connection or do a point to point microwave or other wireless connection I would subnet them to cut down on unnecesary broadcast traffic. Essentially if you have DNS or WINS servers and a router that can route the traffic between those two subnets you shouldn't run into any application issues.

 

[iolair]

@baddos - There is one repeater in each building, where the Cat3 comes into the building. They are not exactly ethernet repeaters in the old sense. They do some sort of media conversion, but I am not exactly sure how they do it. The original units that were here when I got here were a product called Tut repeaters, which I think converted the ethernet (yes, we were 10BaseT back then) to some sort of telephone grade signal. I do know that it's half duplex, and although I've upgraded the Tuts to Patton Ethernet Extenders, it's still half duplex. Patton claims they do 50Mbps, but I'm thinking more like 20 - 25Mbps.

Thanks for the info on the broadcasts. I think my biggest concern is I wanted the users in the remote building to be able to "find" or more accurately, access a file server and email server in the main building. There is a DHCP server and a WINS server in the remote building.

Iolair MacWalter
Network Engineer

 

[baddos]

If you have a WINS or DNS server, you should have no problem finding computers provided they are all properly configured.

 

[iolair]

I have both, actually. Trying to phase out the WINS server and NetBIOS, but still have them in place. I understand that NetBIOS is very chatty on the wires.

Iolair MacWalter
Network Engineer