Archive pour mai 2009

Enable DHCP Relay on a Cisco router

20 mai 2009
We have seen (here) that a Cisco router can act as a DHCP server on a small network. However, DHCP is a problem when trying to install a DHCP service on a dedicated server which is not on the same subnet as  clients.

In this article, we study how to activate the DHCP relay on the router to forward requests from clients located on a different network.

To better understand the problem, we will quickly  review the functioning of DHCP protocol.

Implement a HTTP tunnel on a Linux server

15 mai 2009

In this article, we will learn how to set up a HTTP tunnel between a PC and a Linux server with the SSH protocol to secure our transactions through a firewall or another.

Before to begin any technical part, I will try to explain the operation of Port Forwarding and why implement it.

To understand this concept, I refresh your memories on the communication of computer:

To exchange informations, computers need an IP address and a port number. The port number is important because it’s thanks to it that the communication exists. Client and server have to communicate on the same port number.

Now, we decrypt the Port Forwarding. The Port Forwarding consist of redirect informations sent on a port number of a computer to a different port number on another computer.

» En lire plus:Implement a HTTP tunnel on a Linux server

Activer la fonction DHCP Relais sur un routeur Cisco

11 mai 2009

Nous avons vu précédemment (ici)  qu’un routeur Cisco peut faire office de serveur DHCP sur un réseau de petite taille. Cependant, le protocole DHCP pose un problème lorsque l’on veut installer un service DHCP sur un serveur distinct qui n’est pas dans le même sous -réseau que les clients.

Dans cet article, nous allons étudier comment transformer le routeur en relais DHCP afin de transmettre les requêtes des clients qui se trouvent sur un réseau différent.

Pour mieux comprendre le problème, nous allons revoir rapidement le fonctionnement du protocole DHCP.

» En lire plus:Activer la fonction DHCP Relais sur un routeur Cisco