LinuxQuestions.org
Register a domain and help support LQ
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices



Reply
 
Search this Thread
Old 10-17-2012, 05:25 PM   #16
Lone_Wolf
Member
 
Registered: Jul 2007
Location: Netherlands
Distribution: Archlinux x86_64
Posts: 48

Rep: Reputation: 20

While gateway and dhcp server CAN share an ip-address they are often separated.

I've looked back at the nmap scan you posted, combining that with the other info we got it looks like this to me :

Your pc seems to be connected directly to the internal network of your isp .

This can be achieved by configuring CT-5372 to work as a bridge/modem instead of a router/modem.
Basically a bridge has 2 ports. every network signal it receives on a port is send to the other port.

I have a strong feeling the guy from your isp that changed your network gear messed up bigtime.
I advise you to contact your ISP.
 
1 members found this post helpful.
Old 10-17-2012, 06:29 PM   #17
rknichols
Senior Member
 
Registered: Aug 2009
Distribution: CentOS
Posts: 1,624

Rep: Reputation: 677Reputation: 677Reputation: 677Reputation: 677Reputation: 677Reputation: 677
I have to agree with the Wolf. This is very odd. It looks like the router portion of that device has been configured with NAT disabled, and if you can't get in to configure the internal firewall or other features it might well have been set up as just a switch. Anyway, this is different enough from the way such devices are usually configured that I would be reluctant to try to get in and change anything without instructions from the ISP.

When you connected to 192.168.0.1 did you even get a prompt for an ID and password? That "wlan0" interface name suggests that you were using a wireless connection, and it is common (and highly recommended) for routers to disallow administrative access via a wireless connection.

You can find the address for your DHCP server by looking for a filename ending in ".leases", perhaps /var/lib/dhclient/dhclient-wlan0.leases . Look for "option dhcp-server-identifier".
 
1 members found this post helpful.
Old 10-18-2012, 10:29 AM   #18
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
Quote:
Originally Posted by rknichols View Post
I have to agree with the Wolf. This is very odd. It looks like the router portion of that device has been configured with NAT disabled, and if you can't get in to configure the internal firewall or other features it might well have been set up as just a switch. Anyway, this is different enough from the way such devices are usually configured that I would be reluctant to try to get in and change anything without instructions from the ISP.

When you connected to 192.168.0.1 did you even get a prompt for an ID and password? That "wlan0" interface name suggests that you were using a wireless connection, and it is common (and highly recommended) for routers to disallow administrative access via a wireless connection.

You can find the address for your DHCP server by looking for a filename ending in ".leases", perhaps /var/lib/dhclient/dhclient-wlan0.leases . Look for "option dhcp-server-identifier".
I got a prompt, yes, and when I connected to the router, I used a cat5e cable instead of the wireless.
 
Old 10-20-2012, 04:17 PM   #19
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
Anyway, my crazy setup aside, what else is there to be said about networking?
 
Old 10-22-2012, 03:34 AM   #20
Lone_Wolf
Member
 
Registered: Jul 2007
Location: Netherlands
Distribution: Archlinux x86_64
Posts: 48

Rep: Reputation: 20
Plenty, but let's delve a bit in basic subnetting first.

The company you work for is planning to setup shop at a new location and you will be the senior sysadmin responsible for the network setup on the new location.

Higher Management has indicated the following requirements need to be met :

The new location has 3 departments : office , R&D and Production.

- Office will start with 20 people, but will grow to 40 over time.
Each office worker needs their own pc.

- R&D will have 14 people, but expects to need many special pcs/networked devices.
They estimate the number will be around 60 systems initially, but need room to grow up to 100 systems.

- Production requires 34 systems to start, and needs room to atleast double that for future expansion.

Quality Control will be taken care of by R&D, and they will work closely together with production.
Upto 20 dedicated servers will be needed.

Company IT policy is to use firewall/routers to keep departments isolated from eachother as much as possible.
Dedicated servers also need to be kept separate.

You are given the 132.254.192.0/20 network for the new location and are told by your boss to keep atleast half of that range reserved for the future.

How many subnets will you setup ?
How many firewall/routers do you need ?

How do you propose to divide the ip range over the subnets ?

Last edited by Lone_Wolf; 10-23-2012 at 03:31 PM.
 
1 members found this post helpful.
Old 10-22-2012, 06:50 PM   #21
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
0_o OK then, what is a subnet? Is it the same thing/related to the netmask/subnet mask?

Last edited by MetaMan; 10-22-2012 at 06:57 PM.
 
Old 10-23-2012, 05:03 AM   #22
Lone_Wolf
Member
 
Registered: Jul 2007
Location: Netherlands
Distribution: Archlinux x86_64
Posts: 48

Rep: Reputation: 20
from wikipedia https://en.wikipedia.org/wiki/Subnetwork

Quote:
A subnetwork, or subnet, is a logically visible subdivision of an IP network.[1] The practice of dividing a network into two or more networks is called subnetting.
The location will use the network 132.254.192.0/20 , but you have to divide that in several smaller networks.
Those are called subnets .

Last edited by Lone_Wolf; 10-23-2012 at 03:30 PM.
 
1 members found this post helpful.
Old 10-23-2012, 10:04 AM   #23
rknichols
Senior Member
 
Registered: Aug 2009
Distribution: CentOS
Posts: 1,624

Rep: Reputation: 677Reputation: 677Reputation: 677Reputation: 677Reputation: 677Reputation: 677
The first issue will be that 132.254.192.0 looks a lot more like a /20 than a /12. Looks like someone was counting the remaining part of the address rather than the network mask.
 
1 members found this post helpful.
Old 10-23-2012, 03:30 PM   #24
Lone_Wolf
Member
 
Registered: Jul 2007
Location: Netherlands
Distribution: Archlinux x86_64
Posts: 48

Rep: Reputation: 20
Good catch, rknichols.
You are right, it's a /20 network.

I've edited the posts to correct that.
 
1 members found this post helpful.
Old 10-24-2012, 06:56 PM   #25
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
OK, I've been doing some reading, and I'm having some trouble grasping the concept of subnets. Everything I read says they are used to divide a network and keep machines from talking to each other, but the how is what I'm wondering. Let's say I have the network 192.168.1.0/24. How do I break this up into subnets? How would I actually configure this on a computer or router (whichever would have to be configured)? What is preventing the networks talking to each other-- the router? I keep reading about something called a routing table. What's the binary process involved?

Thanks for all your help so far!

EDIT: ORRRR am I making everything over-complicated and a subnet has pretty much all the properties of a regular network? Would 132.254.192.0/21 be a subnet of 132.254.192.0/20?

Last edited by MetaMan; 10-24-2012 at 07:07 PM.
 
Old 10-31-2012, 02:55 PM   #26
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
Also, along with the questions in the previous post, would it be possible to turn on NAT on the second router which I do have control of? (The router currently functioning as a switch)
 
Old 10-31-2012, 08:28 PM   #27
Lone_Wolf
Member
 
Registered: Jul 2007
Location: Netherlands
Distribution: Archlinux x86_64
Posts: 48

Rep: Reputation: 20
A subnet is a regular network, what is called a subnet and a network is a matter of perspective.

132.254.192.0/21 is indeed a subnet of 132.254.192.0/20 .
132.254.192.0/20 is a subnet of 132.254.0.0/16 .

devices in different networks can not talk to eachother without the assistance of a router.
so the router doesn't block networks from talking to eachother, it enables the communication between networks.

subnets are configured on/with routers, and routers use routing tables to keep track of the networks they know.
computers also have a routing table, but this is normally a simple table with just a few entries.

In principle it 's possible to turn on nat on your second router, but routers use special protocols to talk with eachother.
isp provided modem/routers are often not setup to communicate with routers over their lan ports, only through their wan port.
getting such a setup working can be tricky and is hard to do from a distance.

Last edited by Lone_Wolf; 10-31-2012 at 08:30 PM.
 
1 members found this post helpful.
Old 11-01-2012, 03:36 PM   #28
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
OK, then how would I set up a network with two subnets? I would need two routers, from what I can tell, but where would I go from there? How does NAT work in with subnets? Is a network behind NAT considered a subnet?
 
Old 11-01-2012, 05:27 PM   #29
Lone_Wolf
Member
 
Registered: Jul 2007
Location: Netherlands
Distribution: Archlinux x86_64
Posts: 48

Rep: Reputation: 20
NAT is a special technique that only is used on ipv4 and has little to do with subnets.
To understand more about NAT, start with reading about private networks : http://en.wikipedia.org/wiki/Private_network

The so-called router you get from an isp is typically 3 devices in one :
- modem
- router
- switch

it is designed to handle only 2 networks : an internal lan, and the external internet.

Many (cheap) consumer grade routers have built-in switches, but for network topology they are 2 devices: a router and a switch.

Diagrams will make explaining routing and subnets much easier, but i currently don't have a program to do that.
I'll look into programs to create network diagrams on linux, if i can't find one i guess i'll fallbakc to MS visio.
 
1 members found this post helpful.
Old 11-02-2012, 10:58 AM   #30
MetaMan
Member
 
Registered: Apr 2011
Distribution: Arch Linux :D
Posts: 50

Original Poster
Rep: Reputation: 0
For diagrams, check out Dia. I know it has stuff for networking in it.
 
  


Reply

Tags
broadcast, dhcp, netmask, network, networking


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
host with 221.132.43.105 IP address and 255.255.0.0 netmask. ddomiray Linux - Server 3 10-27-2009 08:06 AM
What is this -> SRC=0.0.0.0 DST=255.255.255.255 LEN=328 TOS=0x00 PREC=0x00 TTL=128 ID carves Linux - Networking 5 08-17-2008 10:26 PM
255.255.253.0 netmask? honychurch Linux - Networking 2 06-07-2007 12:01 AM
Logs full of hits to 255.255.255.255; how to stop logging? mac_phil Mandriva 2 02-23-2004 11:25 AM


All times are GMT -5. The time now is 04:33 PM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration