A-DHCP-Presentació_anglès.pdf

Web Services and Internet CFGS ASIX UF8. UF1.NF1. DHCP INS Bosc de la Coma 1. Introduction UF1. NF1. DHCP DHCP (Dynamic Host Configuration Protocol). DHCP allows the configuring of IP addresses, masks, defaul...

Web Services and Internet CFGS ASIX UF8. UF1.NF1. DHCP INS Bosc de la Coma 1. Introduction UF1. NF1. DHCP DHCP (Dynamic Host Configuration Protocol). DHCP allows the configuring of IP addresses, masks, default gateways, and other parameters in a completely dynamic manner. DHCP is a client-server service. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 2. Benefits UF1. NF1. DHCP Avoids errors and IP address conflicts. Centralises the management. Saves time. Simplifies the management. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 3. Exemples of usage of DHCP UF1. NF1. DHCP The following are a few examples of usage of the DHCP service: In a library which allows for Wi-Fi connections, clients will obtain concessions for a reduced time. For example, minutes. An Internet user who receives at their home system a dynamic IP address from their Internet Service Provider (ISP) will probably have a concession for hours. In the corporative network of a company which has been dynamically set up using DHCP, their systems will obtain a dynamic concession for very long periods of time. For example, days. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 4. Configuration Parameters UF1. NF1. DHCP The basic necessary parameters are: IP Address (unique in the whole network). Mask (separates the network address and the host address). With these two we can already access the network. If we want to access external networks we need to set up the default gateway. The fourth most habitual parameter is the DNS server group, which will be explained later. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 5. Setup Example UF1. NF1. DHCP Host 1: IP Address: 192.168.1.232 Mask: 255.255.255.0 Gateway: 192.168.1.1 Host 2: IP Address: 192.168.1.36 Mask: 255.255.255.0 Gateway: 192.168.1.1 The mask indicates that the network portion is 192.168.1. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 6. The DHCP protocol and its UF1. NF1. DHCP components The DHCP protocol is defined by an official document called RFC. As it happens with all client-server protocols, a dialogue will exist between 2 systems. This dialogue will have to be analyzed to know which it is and how it is produced. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 6. The DHCP protocol and its UF1. NF1. DHCP components The functional model of the DHCP protocol: The DHCP service (server) listens to petitions through port 67 UDP. Clients receive the DHCP informations through port 68 UDP. Why UDP? It does not need a continuous flux of information. There can be different DHCP servers within the same network. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 6. The DHCP protocol and its UF1. NF1. DHCP components The negotiation follows these steps: 1.The client sends a discovery message for an IP address + network configuration. 2.The server checks available IP addresses within its allowed range and sends an offer with one. 3.If the client accepts they send a request. 4.The server then acknowledges the request and leases it for a limited period of time. 5.Once the lease time is over, the IP configuration must be renewed. 6.DHCP also allows other processes like information requests or releasing of IPs. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 6. The DHCP protocol and its UF1. NF1. DHCP components DHCP negotiation diagram: INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 6. The DHCP protocol and its UF1. NF1. DHCP components The different types of DHCP packages are: DHCP discover. DHCP offer. DHCP request. DHCP ack (acceptance) / DHCP nack (refusal) DHCP decline. DHCP release. DHCP information. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 6. The DHCP protocol and its UF1. NF1. DHCP components Considerations: The server usually needs to know the client’s MAC address. This way, the server can always give the client the same concessions. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll 7. Important concepts UF1. NF1. DHCP IP Address Conflicts: it can happen with dynamical allocation if the DHCP service is incorrectly configured. IP Address Range: which range can be leased to the different clients. Exclusions: IP addresses which won’t be leased to clients. Concessions: IP address and network configuration leased to a particular client. Reserves: IP addresses assigned via DHCP, but always to the same host. INS Bosc de la Coma Autor: I. Ricart, J.Rodríguez, S. Coll