Sunday, March 29, 2015

Cisco – Router as a DNS Server

As many didn’t know (me included) you can configure cisco router as DNS server.

A cisco router can:

Reply to requests for locally defined DNS entries.
Forward the request the public DNS servers (max 6)

In the cenario bellow we are going setup and test this.

Configs

-- R1 --

interface FastEthernet0/0
description *** LAN ***
ip address 192.168.1.254 255.255.255.0
no shutdown

interface FastEthernet0/1
description *** WAN ***
ip address 200.0.0.2 255.255.255.252
no shutdown

ip route 0.0.0.0 0.0.0.0 200.0.0.1 name DefaultRoute

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Enable the router as a DNS server
! and domain lookup on the router
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
ip dns server
ip domain-lookup

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Public name-servers, for the router to query
! the names it doesn't know
! Maximum 6x DNS servers
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
ip name-server 4.2.2.5
ip name-server 4.2.2.6

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Local DNS Entries
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
ip host PC1 192.168.1.1
ip host PC2 192.168.1.2
ip host PC3 192.168.1.3

The big secret here is the “ip dns server”, because the rest of the config you could have it to solve name locally on the router.

With the “ip dns server” you extend the router’s local name resolution, to the hosts on the network.

-- PC1 --

The PCs on my topology are actually routers so here is my config:

-- PC1 (Router) --
interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

ip route 0.0.0.0 0.0.0.0 192.168.1.254 name GW

ip domain-lookup
ip name-server 192.168.1.254

-- PC2 (Router) --
interface FastEthernet0/0
ip address 192.168.1.2 255.255.255.0
no shutdown

ip route 0.0.0.0 0.0.0.0 192.168.1.254 name GW

ip domain-lookup
ip name-server 192.168.1.254

-- PC3 (Router) --
interface FastEthernet0/0
ip address 192.168.1.3 255.255.255.0
no shutdown

ip route 0.0.0.0 0.0.0.0 192.168.1.254 name GW

ip domain-lookup
ip name-server 192.168.1.254

Tests

-- Test the Local Entries for The PCs on the LAN --

PC1#ping PC2
Translating "PC2"...domain server (192.168.1.254) [OK]

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 1/1/1 ms

PC1#ping PC3
Translating "PC3"...domain server (192.168.1.254) [OK]

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/5 ms
PC1#

-- Test Forwarding Request to Public DNS Servers--

PC1#ping www.google.com

Translating "www.google.com"...domain server (192.168.1.254) [OK]

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 216.58.208.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/69/84 ms

Related Links:

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/257-cisco-router-dns-server.html

Monday, March 2, 2015

Cisco IOS on UNIX (IOU) – On GNS3 v1.x

Today I’m going to discuss How to install and configure Cisco IOU in GNS3-1.2.1. In this way you can emulate Cisco Switch in GNS3. This article explains to get a working layer 2 switch in GNS3-1.1. Cisco IOS on UNIX (IOU) is a fully working version of IOS that runs UNIX/LINUX platform. Cisco IOS on UNIX is intended for Cisco employees for research and experiments. Distribution of IOU images to customers or external persons is strictly prohibited.

Tools required
Import GNS3 IOU VM.ova
Uploading IOU image to UNIX
GNS3 Local and Remote Server
IOS on UNIX Configuration for GNS3

Tools required

GNS3-1.2.1
Oracle VirtualBox
GNS3 IOU VM.ova:- Is the Virtual UNIX platform to run IOU image. It is a virtual box OVA file.
IOU image: IOU image is intended to use only for Cisco employees, distribution of IOU is strictly prohibited. Please don’t ask me! Google is your friend always.
iourc.txt file: Is the license of Cisco IOU image. I have no privilege to provide it publically, but I found a discussion related to it here. It may help you.

Step 1: Import GNS3 IOU VM.ova

Import GNS3 IOU VM.ova to VirtualBox.

Go to Settings → Network → Adapter 1. Make sure it is attached to Host-only Adapter with name VirtualBox Host-Only Ethernet Adapter. Then click OK.

Start the GNS3 IOU VM, and login with following credentials.

User name : root
Password : cisco

Step 2: Configuring the GNS3 IOU VM Ethernet Adapter

First define the IP of the eth0 interface on GNS3 IOU VM:

nano /etc/network/interfaces

save the interface configuration: Ctlr+X – Yes

Next restart the eth0 (down/up) interface, so that it loads the configuration from the /etc/network/interfaces file

If you restart the VM, the initial banner will shows the configured IP, along with the Web interface URL that we will use latter to load IOU images.

On your computer set the VirtualBox Host-Only Ethernet Adapter with an IP in the same network.

Go to Control Panel → Network and Internet → Network Connections

to test that you have a connection between you computer and the VM, ping the VM from your computer:

Step 3: Uploading IOU image to UNIX

Check the IP address of the GNS3 IOU VM by issuing ifconfig (or as seen on step 2) command and note down the IP (mine 192.168.56.102). Now open any web browser in host machine and enter the following link in the address bar:

http://192.168.56.102:8000/upload