ConfigBytes

Twitter Weekly Updates for 2010-03-07

rstaples — Sun, 07 Mar 2010 08:17:00 +0000

Just finished upgrading my system – sporting win 7 64bit – installing gns3 now http://twitpic.com/15shz8 #

GNS3 07 ?

rstaples — Mon, 01 Mar 2010 07:15:53 +0000

So far I am not pleased with the new GNS3 07 , I’m having some serious issues in

Qemu

trying to configure the settings.
Searching the internet has not yeilded much information on how to set this up. This week I’ll be “plunking” around with the new GNS3, trying to make it work. I hope to have it all figured out soon so I can upload my PIX labs that I’ve been working on.

Twitter Weekly Updates for 2010-02-28

rstaples — Sun, 28 Feb 2010 08:17:00 +0000

Updating the web site… again #

IPv6 is alive and being used on the internet.

rstaples — Fri, 20 Nov 2009 17:31:12 +0000

VirtualBox: access Windows-host

rstaples — Thu, 12 Nov 2009 19:06:56 +0000

Here’s a nice snippet I found when looking for help guest to host file sharing.

VirtualBox: access Windows-host shared folders from Ubuntu-guest
This is the scenario that you run Windows as your host operating system and Ubuntu in a VirtualBox, and that you want to access a specific Windows folder from Ubuntu.

First you have to make sure that have install Guest Additions. From the VirtualBox’s menu go to Devices → Install Guest Additions… This will mount a virtual CD on your /media/cdrom. Normally this folder’s window will show up. As root run the program VBoxLinuxAdditions.run. When the program completes reboot your VirtualBox.

The Last Subnet How2 Doc v3.0

rstaples — Tue, 20 Oct 2009 13:52:19 +0000

Note that this was originally posted in May 2009

I wrote this document to help with my CCNA studies, the intent of the document was to help me quickly convert class A and B subnets for the test. The CCNA will present subnet questions in CIDR format and you should know how to answer them in less then 90 seconds.

I converted the document from Microsoft Word 2007 to PDF using doPDF6.3 a free PDF converter. So far it appears to have done a nice job. You can find it here >Do PDF

The document is here > The Last Subnet How2 Doc

Please let me know of any errors, spelling or grammar.

(Last edited by rstaples on 20, October 2009 at 08:00 – for grammar and spelling)

Network Address Translation

rstaples — Fri, 16 Oct 2009 21:31:02 +0000

Network Address Translation, sometimes called Network Address Translator (NAT), was originally outlined in RFC 1631 in 1994. This was to allow devices on the inside network the use of private IP addresses that are presently defined in RFC 1918. NAT makes it possible to have a very big internal network with thousands of local addresses represented by a handful of global addresses or possibly a single global address.

We will setup a basic static and dynamic NAT configuration.

To the left we have a basic example of how NAT operates. Starting from the bottom we have our …

Inside Local Addresses
Outside Local Address
Inside Global Address
Outside Global Address

Our ISP has given us the following IP range. 189.45.23.56/29, looking at this subnet we can tell that our network starts on the 8^th subnet range and this will give us 6 useable addresses

(For simplicity we will not be using subnet-zero)

Network ID: 189.45.23.56
First usable address: 189.45.23.57
Last usable address: 189.45.23.63
Broadcast address: 189.45.23.64
Netmask of: 255.255.255.248

Now we know that our usable range will be from 189.45.23.57 to 189.45.23.63 for a total of 6 addresses. 189.45.23.57 is already being used for out serial0 interface of our router. That leaves us five useable hosts.

For our INSIDE LOCAL address, I would like to reserve the IP of 189.45.23.58; this will point to our company’s web server. For this we will need to configure a static nat. Once we complete this configuration we will be left with four usable hosts.

Router#config t
Router(config)# ip nat inside source static 192.168.1.125 189.45.23.58

The above config shows that 192.168.1.125 will be known as 189.45.23.58 to the outside world.Next we must configure our host 192.168.1.125 from accessing our NAT pool. Let’s start by setting up or NAT pool

1. Router#config t
2. Router(config)# ip nat pool MyPool 189.45.23.59 189.45.23.63 netmask 255.255.255.248
3. Router(config)# access-list 1 deny host 192.168.1.125
4. Router(config)# access-list 1 permit 192.168.1.0 0.0.0.7
5. Router(config)# ip nat inside source list 1 pool MyPool
6. Router(config)#int e0
7. Router(config-if)#ip nat inside
8. Router(config-if)#exit
9. Router(config)#int s0
10. Router(config-if)#ip nat outside
11. Router(config-if)#exit
12. Router#

Line 3 prevents host 192.168.1.125 from accessing our NAT pool, he already has an IP.

Line 4 allows the remaining hosts to access the NAT pool.

Line 5 defines our pool to access-list 1, lets him know what security rules to follow.

Lines 6 through 10, we apply the access-list to our inside (e0) and outside (so) interfaces.

That completes our basic static and dynamic NAT configuration.

What have we done?

Configured a static nat for our inside web server.

Configured a dynamic NAT, to allow our hosts access to the internet.

Keep in mind that above configuration does NOT allow much room for growth , also that we start with six useable hosts and we lost two before we even got started configuring our NAT pool. This leaves us with only five usable address of 189.45.23.59, 189.45.23.60 189.45.23.61 189.45.23.62 and 189.45.23.63; for our pool to hand out.

By default NAT allows the hosts to keep the requested IP for 24 hours. The above topology shows that we already have four hosts connected to our switch, if any more users were added to network; they would not be able to access the internet.

This leads us to my next article – PAT (Port Address Translation). Next week we will discuss how PAT many hosts to access the internet on several or one registered internet address. We will discuss the use of nat overloading (Many IP’s to One)

Are you still telneting into your devices?

rstaples — Fri, 16 Oct 2009 21:11:28 +0000

By now I’m sure you’ve already read several articles that explained the pitfalls of using telnet to access your network devices, it’s not a secure way to access your network. Telnet does not offer any encryption, your login and password information is sent across the network in plain text.

Many Cisco devices today allow for SSH configuration. SSH not only allows for encryption of password and login information but also allows you devices to know who is logging in.

SSH can be configured easily on any Cisco device with IOS that supports DES or DES3 (should be using DES3).

Router (config) #username Joe password j03adM1n
Router (config-line) # login local
Router (config) # ip domain-name mylab.local
Router (config) # crypto key generate rsa
Router (config) # line vty 0 4
Router (config-line) # transport input ssh

Once you have your router configured for SSH, you will need to use a terminal program that supports SSH, such as PuTTY, Tera Term or SecureCRT. Windows XP and Vista include a command line SSH capability, my personal favorite is SecureCRT.