A question for all you net admins out there

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namatoki
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A question for all you net admins out there

Postby namatoki » Wed Jun 06, 2001 3:04 am

I know I should know the answer to this, but I've been away from networks, so my knowledge is a little rusty. Okay, here's the situation: I have a LAN at home connected through a switch. I use DSL to connect my LAN to the Net. Now the problem is that my ISP only assigns dynamic IPs and the IPs I have are on different subnets. Now, I know that a switch should allow my LAN to function properly, but it seems to slow down a bit at times. Do I need to get a router to fix this? Also, I don't want to get the DSL router/switch combo that allows proxy connections since I am paying for multiple IPs and I'd rather use them all. Any ideas?

Nizrath
Kiloppile
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Postby Kiloppile » Wed Jun 06, 2001 3:06 am

There's no technical reason that your switch should cause a problem. From my experience DSL is just a bit flaky.

Hrm. Are they actually giving you a subnet mask other than 255.255.255.0?

[This message has been edited by Kiloppile (edited 06-05-2001).]
namatoki
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Postby namatoki » Wed Jun 06, 2001 3:16 am

My problem isn't my DSL. It's my intranet that's slowing down. The thing is that it's very random and I don't get a chance to do any pinging to measure the slow downs.

As for the subnet, it's not the subnet mask that's the problem, it's the IPs being on different subnets. For example, xxx.xxx.54.70 is on a different subnet than xxx.xxx.140.65.
Kiloppile
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Postby Kiloppile » Wed Jun 06, 2001 3:24 am

Hrm... never have messed with a situation like that. Sorry.

From chatting with a friend though, I'm suspecting that if you try to communicate *between* those two machines, it's actually going to get routed up through the dsl and then back down. Would be alot slower than if you had ip's in the same range.

[This message has been edited by Kiloppile (edited 06-05-2001).]
Malacar
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Postby Malacar » Wed Jun 06, 2001 5:28 am

Why are you using different networks? Just break up the private class C you have(24 bit mask) to a smaller mask(maybe 25 or 26 bit). You'd alleviate most routing issues, just would have to create a static route for the class c mask, and it'd route everything without touching your dsl.

Or, if you have a switch, and know routing well, just program a bunch of static routes for your private networks that don't point to the(I assume) NAT'd IP.

Meaning... Keep all the routes internal, and seperate them from the external interface totally. Otherwise they will use the default route, which would poke down the DSL line to THEIR router, then come back to yours...

Hope this wasn't too cryptic.. Am tired, Red Sox game just got over.. Feh, screw 18 innings.

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Malacar - French kissin midgets, and damn proud of it. Oh yeah... My comments can offend you now, I don't care anymore. Have a day.
imp
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Postby imp » Wed Jun 06, 2001 12:23 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><font face="Verdana, Arial" size="2">Originally posted by Kiloppile:
<B>Hrm... never have messed with a situation like that. Sorry.

From chatting with a friend though, I'm suspecting that if you try to communicate *between* those two machines, it's actually going to get routed up through the dsl and then back down. Would be alot slower than if you had ip's in the same range.

[This message has been edited by Kiloppile (edited 06-05-2001).]</B></font><HR></BLOCKQUOTE>

Yes thats correct, you need to set up your own router or else the DSL box will act (as it is acting atm) as a router since adresses are from different networks.

Ask your isp if you could get all adresses from the same scope to your DSL box or open your wallet and by a router.

/Bogra
Jorta
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Postby Jorta » Wed Jun 06, 2001 1:41 pm

Hi Namatoki,

I think a bit more data is needed in order to fully diagnose the problem. You don't have a sniffer on your network do you? If you don't you can play with Ethereal for free (www.ethereal.com). It would be key to know what you are doing at the time it slows down.

Barring that, I think Kiloppile has the right idea. I would assume that the two machines are trying to do something using IP (what I don't know without looking at your network)and each machine is sending to its default gateway in order to have it routed back down the DSL pipe to your other machine on the switch.

Also you may want to look at your DNS servers. If one of them is browning out or otherwise performing poorly they can give the illusion of poor performance while waiting for name resolution.

If you get some more detail go ahead and email me at criggs@hill.com.

Also, you may want to look into some DSL routers that allow multiple IP addresses to be assigned to the serial interface (well, ok its an outbound Ethernet...) and can IP forward them to different machines internally. I only had about 10 seconds to look at the linksys site and did not find that feature on their routers but I thought they supported it. Try netgear or search on www.practicallynetworked.com. They have many reviews on switch/routers and one of them may do the trick for you.

Good luck!

Jorta
Kiloppile
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Postby Kiloppile » Wed Jun 06, 2001 3:38 pm

It does strike me as a little *odd* that they would be assigning you IP's in different ranges like that.

I'm thinking that if the subnet mask isn't 255.255.0.0 they're just not going to see each other without manually setting up some interesting routing tables.

Incidentally, Mal, we're all assuming this isn't NAT'd addresses, as he says he's being assigned them by the DSL service.
Kiloppile
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Postby Kiloppile » Wed Jun 06, 2001 3:40 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><font face="Verdana, Arial" size="2">Originally posted by Malacar:
<B>Why are you using different networks? Just break up the private class C you have(24 bit mask) to a smaller mask(maybe 25 or 26 bit). You'd alleviate most routing issues, just would have to create a static route for the class c mask, and it'd route everything without touching your dsl.

Or, if you have a switch, and know routing well, just program a bunch of static routes for your private networks that don't point to the(I assume) NAT'd IP.

Meaning... Keep all the routes internal, and seperate them from the external interface totally. Otherwise they will use the default route, which would poke down the DSL line to THEIR router, then come back to yours...

Hope this wasn't too cryptic.. Am tired, Red Sox game just got over.. Feh, screw 18 innings.

</B></font><HR></BLOCKQUOTE>

Did the Sox win though? Always leaves me with a good feelin' in those long-ass games if my team wins! Image
Jorta
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Postby Jorta » Wed Jun 06, 2001 4:14 pm

In most cases, there is nothing wrong with Namatoki's IP being on different subnets. I agree with the esteemed halfling that its odd, but not unheard of. At least several network configurations spring to mind where this might be the case. Most routers are able to support different IP addresses and network masks on one interface. This only causes problems if the clients need to speak to each other, not in the case of client traffic being sent outbound which is what the designers of your DSL network assume. Also depending on your DSL provider you may be using PPPoE in which case your just getting passed back from your telco to another ISP (or your telcos ISP) through an ATM PVC which is grabbing IPs from any number of pools just as it would for dial-in access. If its a national DSL provider this is more likely to be the case.

At the same time, without seeing the mask that is configured on the machines, this question can't be answered.

'For example, xxx.xxx.54.70 is on a different subnet than xxx.xxx.140.65'

Does not have to mean they are on different subnets if it is a /16. Yeah, its a big ol subnet, but it's not contention based (At least for your copper and the PVC to the ISP) and could be part of the RFC 1918 space so there are addresses to burn. Can't know that without seeing those first 16 bits Image

So more info is needed ImageIs there any consistency as to when things slow down? What applications are you running? What OS are you running? Are there other protocols like NetBEUI on your network? Are you sure the security of your machines has not been compromised? Perhaps during these slow downs someone is transferring files you don't know about! In the case of a mystery and barring any clear clues the best thing to do is fire up a sniffer and let it run for a bit. See what is happening on the wire when things slow down.

Finally, if you are still frustrated and don't want to spend the cash on a router get an old 486 and drop a couple of 10MB ISA cards (some of the newer 486's had PCI which is nice 'cause I find ISA hard to find now) in them, throw one of the many router/floppy boot linux's on there and make a router. Drop it between your DSL modem and your switch and you are ready to rock: Two 'real' IP addresses forwarded to two NAT'd IPs on your workstations. Workstation LAN is part of the same network and works fine and still can communicate with the outside world looking like it came from different IP addresses. You could even throw a simple packet filtering firewall on it too. Might as well get supplement your personal firewalls as well (you do have personal firewalls on your machines don't you Image). All of this for under $30 if you already have the 486. If you don't have the 486 start looking in closets. Someone has one they will give you.

Jorta
Niple
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Postby Niple » Wed Jun 06, 2001 4:24 pm

Gonna have to agree with Malacar on this one. If you happen to be running Win2000 you can set it up to do your routing and NAT (Network Address Translation). Using this method you would be able to just subscribe to one IP address but let Win2000 take care of your DNS and DHCP. What this will also allow you to do is set up your own private intranet, allowing you to get as many computers online as you want and still only physically use one IP from your ISP. Win2000 will do your internal routing and IP addressing for you internally. The only thing you would need to do is install another network card in your computer. You have to have 2 cards to make this work.

If your interested in trying this feel free to email me and I'll walk you through it.

Nip
Niple
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Postby Niple » Wed Jun 06, 2001 4:34 pm

Failed to mention this in my earlier post but if you want a really cheap worry free solution to NAT/routing/DNS/DHCP find yourself an old crappy 486 (hell, a 386 will even work) gut it, except for the motherboard, processor, memory (doesn't have to be much) and 3 1/2 floppy. Doesn't need a hard drive (it boots and runs off floppy). Do a search on the net for FrazierWall and download their free software, its a Linux based firewall/NAT/DNS/DHCP package. Not hard to set up at all, you just have to know the MAC address of your network cards. Once again to make this work, this box will have to have two cards.

Holler at me if I can help.

Nip
Now more than ever, LiNuX RuLeZ!
namatoki
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Postby namatoki » Wed Jun 06, 2001 5:30 pm

Wow, thanks for all the info, guys! I didn't get a chance to completely read through all the threads yet, but I will soon and hopefully, I can figure something out.

Here are some answeres to some questions brought up. My ISP is using DHCP to assign IPs, and I really have no clue why I got stuck with IPs on completely different subnets. My IPs are class B (since they are in the 130.xxx.xxx.xxx range). I do have a 10/100 switch that my LAN is connected through (and thus I am *not* using a stupid spammy hub). Unfortunately, I am not using Windows 2000, but I have Windows ME running on all my machines. Also, I forgot to mention that the only way my network could see each other was by setting up IPX/SPX, but I really do not want to be using this protocol any longer. If I do have to plunk down money for a router, I really don't mind, it's the setting up that I might have problems with. Thanks again guys!
Malacar
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Postby Malacar » Wed Jun 06, 2001 5:43 pm

Yup! Sox won.

Shea Hillenbrand smacked a solo home run in the bottom of the 18th at 12:57am est. ;P

Namakatomi... Upgrade! Image

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Malacar - French kissin midgets, and damn proud of it. Oh yeah... My comments can offend you now, I don't care anymore. Have a day.
Jorta
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Postby Jorta » Wed Jun 06, 2001 7:10 pm

Just a side note after breezing over the board again: With the introduction of RFC 1519 (CIDR) the rules of class A, B, and C addresses were totally erased. An IP address is meaningless without the subnet mask now. The class D and E address have been preserved as address spaces, but are not used in traditionally routed networks (ok, ok, multicasting aside...). In other words just because an IP address begins with 65. or 130. or 200. you can't assume what the mask is when assigned by a service provider.

This was fun! Thanks for the question!

Jorta the happy geek.
Malacar
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Postby Malacar » Wed Jun 06, 2001 8:15 pm

J:

Explain that to Microsoft! We've found numerous bugs where they -force- a full class subnet on the IP based on it's initial two octets... It's VERY annoying. And quite stressful finding the docs on how to registry hack to fix it. grr....


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Malacar - French kissin midgets, and damn proud of it. Oh yeah... My comments can offend you now, I don't care anymore. Have a day.
Jorta
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Postby Jorta » Wed Jun 06, 2001 8:50 pm

Based on the ediquite for posting on the board - don't even get me started on Microsuck and Windoze. Your right, they still assume classfull address when you enter in an IP address. I suppose if its good enough for RIP its good enough for MS. Although to be fair, generally the actual IP address is going to be some VLSM of the old classful block so just they save me from having to type 255.255. some. Anything more on the subject of how MS does things would steer me towards a particularly ungentleman-like frame of mind. And thats not what I read this board or play the MUD for Image!

But! That does not change that you can't assume the class of an address based upon the first 3 or 4 bits. Especially when assigned by an ISP or other upstream provider.

Peace!

Jorta
imp
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Postby imp » Wed Jun 06, 2001 10:27 pm

Guess you can insert an extra metwork card in each machine too and set em up with private address'es tho not all of us can "borrow" that kind o stuff from work ;)

/Bogra


(oh and you'll need some more free ports in the switch :p )
Nokie
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Postby Nokie » Wed Jun 06, 2001 10:54 pm

Well since we're on the topic of networking, I was bored at work today and drew a little diagram illustrsting the path packets are taking when I use the WinXP Remote Desktop:

http://billimek.com/rd.html

The remote deskop thing is really cool too! I can be conencted to my WinXP box from work and listen to my MP3 collection locally since the Remote Desktop client/server thingy automagically brings sounds to the local computer. I can see my workplace network printers as if they were local printers when I'm connected. It's really cool!

Nokie Quickfingers!

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