Discovering network parameters
 

Hi,

I've been installing a computer room for my son's public school, as previous responsable formated all HD, loosing everything ! 8O
The only problem left (after recollecting drivers all along Internet) is the network: DHCP isn't installed, so I assume I need a fixed ip, but I don't know which!
All computers are connected to a switch/router, connected to a another switch/router, with a ADSL internet connection,
They don't have any architecture about that, so I only have my laptop to get that information.

Is there a tool I can use from my laptop, connecting it directly to the router/switch, to discover the netmask and switch/router ip?

Thanks,
Fabrice

Hi Fabrice,

Install a DHCP server :!:
If not, you'll go crazy with IP management, trying to keep a document of who has what IP.
Get yourself a firewall which has built-in DHCP server, such as m0n0Wall.
Then set up every PC as DHCP client, and forget about it.
Look here: http://m0n0.ch/wall/
And you can install that on a dirt cheap/slow/old Pentium :)

Edit: About the troubleshooting tools, get Freesbie ( http://www.freebsie.org ) and you can use that to connect to your hub and run "tcpdump" so you can analyze the packets ;)
No need to install that, because it runs from the CD :)

-kwag

Hi karl,

I knew you would answer! :)

I just have to convince them not to switch off the general interruptor, when they don't use the room! Right now, the PC are between Pentium 100, and PII 300 Mhz... (they only have 15 PC + 1 for administrative purpose in an other location). I installed w98, but I think I'll install later some with linux/freebsd... Just in order childs see something else than Bill!

They will soon receive new Pc's, so I'll speak with them about that, but m0n0Wall looks great!

Great. I'll give it a try! (first at home, to see possible problems, and the packets! :) ).

Thanks,

Fabrice

Hi fabrice :),
You certainly know what I'm about to write, but nevertheless...
Common LAN IP addresses are:
192.168.1.x
192.168.10.x
192.168.100.x
10.0.0.x
regularly there are no specific subnets so you shoulg go with class C, that is, a subnet of 255.255.255.0
Usually the routers and servers use the lowest or highest IP addresses.
So you routers could be using an IP address of <=10.0.0.5 or >=10.0.0.250.
Or to complete the example <=192.168.1.5 or >=192.168.1.250.
Imagine that the router has an IP address of 10.0.0.1/24.
Then you should setup a PC with an IP address of 10.0.0.100/24.
I give .100 as an example ;-)
In this example you could use any IP from 10.0.0.2..10.0.0.254 :)
Then try to open http://10.0.0.1 on your browser.
Or run a Telnet from the command line "telnet 10.0.0.1".
If it ask for password, good luck trying to figure it out :lol:.
Cheers pal

This leads to nothing except if you have a webserver (apache...) catching port 80 on your PC.

http://s9.yousendit.com/d.aspx?id=1D...K0M1KKYLSJSRCP
http://s5.yousendit.com/d.aspx?id=2Y...619VG1440LGX4T

Whith these 2 tools, do a scan between range given by rds.
You can grab some info about your net.
Also with a tracert from cmd.exe (I don't remember if w98 has this tool) to a external ip or web, will show you which is your router ip, as it will be last private ip.
From cmd.exe console also do a ipconfig /all command.

Indeed, you're right Phil.
That's what happens with many SOHO routers out there.
They come with a mini-webserver built-in for configuration purposes.
This is what fabrice wants, right?
He wants to reconfigure the network/routers, right?
And of course I was guessing that his routers would still have port 80 set for configuration.
It is the default configuration for many of the SOHO products out there.
But maybe you have a better option instead?
Note: Some routers are set for https instead of http!
Cheers

@fabrice,
Judging by Prodaters post I'm starting to believe I didn't understand your original message.
Did I understand correctly that the school's previous IT manager erased all HDD on ALL computers?
Otherwise it is as simple as using winipcfg (w98) or ipconfig (nt/w2k/xp) on one of the good PCs to gather the needed information so that you can rejoin the network from a single PC.
But if the previous IT manager erased all info from all HDDs of all the PCs, then you'll need to start guessing or reset all your networking/routing equipment to factory defaults and redo all it's configuration.
Tracert may not help much since you need to use it on one PC that hasn't seen it's HDD config being erased.
If you use it on a formated/reinstalled PC you will have to use a standard fixed IP address.
Before that, bye bye to all the commands we have been talking about.
This is MHO.
Cheers

My router also has a webserver but you will never find any configured using 10.0.0.1. They generally start with upper adress (mine is 10.0.0.139, but generally it is 10.0.0.254).
Personally I use 10.0.0.1 for my first ethernet card, 10.0.0.2 for the second and 10.0.0.3 for the wifi link. That's why I'm not sure that your idea to test 10.0.0.1 in a browser can be widely used. But may be I'm wrong.

@Phil :)
I thought I had mentioned earlier that router/networking hardware are usually set for low or high IP addresses.
I even gave a few examples.
I just kept on with example using one of the given IP addresses which was 10.0.0.1.
But as said, I'd like to know if all HDDs were wiped out or not.
Cheers

Okay, forget my post :-D

Hi rui,

You're right: there is nothing left in the pc's (19), otherwise, I wouldn't have asked! :) With a simple winipcfg/ipconfig, you get everything you need.

In this case, i'll try tomorrow with fixed ip within the range you specified, and use a scan tool, to see if I'm lucky. I knew the 192.168.1 range, but not the others ones...
on the other hand, I get windump (win equiv to tcpdump), and I'll try to understand a trace!

thanks,
Fabrice

For Class A network, 10.0.0.0 - 10.255.255.255 (10/8 prefix) range (For big network that requires a huge pool of 16 million private IP addresses)

For Class B network, 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) range (For medium-sized network that requires 65000 private IP addresses)

For Class C network, 192.168.0.0 - 192.168.255.255 (192.168/16 prefix) range (Commonly used IP range on smaller network for easier addressing of 254 IP addresses. May not necessarily be smaller network but network managed in smaller blocks.)


-kwag

Hi,

So if I use a fixed ip of 192.168.1.1, and a mask of 255.255.0.0, I should be able to discover the switch/hub/router address with a simple scan?

Fabrice

You may want to keep the subnet mask 255.255.255.0 instead of 255.255.0.0.
Running a software network scanner, most probably you will find the LAN settings.
Karl advised you a tool that I don't know but that should act as an network scanner.
Afterwards it's a question of configuration method your routers have.
Some accept only a telnet session.
Other also accept an http/https session.
Other only accept the upload of a bin file or a text file with the settings.
And you'll need the password for such hardware.
But only if you care to change routing configuration.
If the previous configuration pleased the school headmaster, then you just have to find the IP range for the LAN and configure the PCs/Printers,etc.
Don't forget to set the gateways on your hosts.
You might want to follow Karl's advise and install m0n0wall on one of the old PCs.
It will act as an intermediate between the routers and the PCs and it can act as a DHCP server ;-).
It could even substitute your routers.
Keep us updated ;-)
Cheers

Hi,

After installing m0n0wall on one old PC, I should update the gateway parameter of each PC to use the m0n0wall ip? Or just put them dynamic adress, as m0n0wall act as a DHCP server?

The network has 2 sub-network:
- one connected to the ADSL modem, and one administrative PC connected- Net A
- one for the classroom, with 18 Pc connected- Net B

In this case, after installing m0n0wall, the route to internet would be:
- PC in net B -> m0n0wall -> hub Net B -> hub Net A -> ADSL Modem ?
Before I said that it was a router, but I think it's more a hub, with 24 port...

Thanks,
Fabrice

m0n0Wall will automatically assign IPs and gateway to all PCs in your network.m0n0Wall assigns a WAN and a LAN name to your cards automatically.
Just connect your ADSL modem to the WAN ethernet port, and the internal main hub to the LAN port.
If your ADSL modem assigns IPs, because it has a DHCP server, then m0n0Wall will get an IP and DNSs and gateway automatically.
If not, you neet to assign manually the IP to the WAN port, and also the gateway and DNS servers.

-kwag