Natting - Network Administration - Lecture Slides, Slides of Network and System Administration

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Natting

NATTING

Private vs Public IP Addresses

Whatever connects directly into Internet must have public (globally unique) IP address

There is a shortage of public IPv4 address

So Private IP addresses can be used within a private network

Three address ranges are reserved for private usage 10.0.0.0/ 172.16.0.0/16 to 172.31.0.0/ 192.168.0.0/24 to 192.168.255.0/

A private IP is mapped to a Public IP, when the machine has to access the Internet

Natting

NAT

Static NAT : Maps unique Private IP to unique Public IP

Dynamic NAT : Maps Multiple Private IP to a Pool of Public IPs (Port Address Translation : Maps a Public IP and Port Number to a service in Private IP)

Natting

H

Private address: 10.0.1. Private network

Source = 10.0.1. Source port = 2001

Source = 128.143.71. Source port = 3200

NAT

H

Private address: 10.0.1. Source = 10.0.1. Source port = 1090

Internet Source = 128.143.71. Destination = 4444

128.143.71.

SNMP

SNMP

SNMP

SNMP is based on the manager/agent model consisting of a manager, an agent, a database of management information, called as MIB. The manager provides the interface between the human network manager and the management system. The agent provides the interface between the manager and the physical device(s) being managed.

SNMP

SNMP

SNMP uses five basic messages (GET, GET-NEXT, GET- RESPONSE, SET, and TRAP) to communicate between the manager and the agent. The GET and GET-NEXT messages allow the manager to request information for a specific variable. The agent, upon receiving a GET or GET-NEXT message, will issue a GET- RESPONSE message to the manager with either the information requested or an error indication as to why the request cannot be processed. A SET message allows the manager to request a change be made to the value of a specific variable in the case of an alarm remote that will operate a relay. The agent will then respond with a GET-RESPONSE message indicating the change has been made or an error indication as to why the change cannot be made. The TRAP message allows the agent to spontaneously inform the manager of an ‘important’ event.

SNMP

VPN

VPN is a private connection between two systems or networks over a shared or public network (typically Internet). VPN technology lets an organization securely extend its network services over the Internet to remote users, branch offices, and partner companies. In other words, VPN turns the Internet into a simulated private WAN. VPN is very appealing since the Internet has a global presence, and its use is now standard practice for most users and organizations.

VPN

VPN

VPN

How VPN Works

VPN overcome these obstacles by using a strategy called Tunneling. Instead of packets crossing the Internet out in the open, data packets are fist encrypted for security, and then encapsulated in an IP packet by the VPN and tunneled through the Internet.

The VPN tunnel initiator on the source network communicates with a VPN tunnel terminator on the destination network. The two agree upon an encryption scheme, and the tunnel initiator encrypts the packet for security.

VPN

Advantages of Using VPN

VPN technology provides many benefits. Perhaps the biggest selling point for VPN is cost savings. One can avoid having to purchase expensive leased lines to branch offices or partner companies. On another cost-related note, you can evade having to invest in additional WAN equipment and instead leverage your existing Internet installation.

Another benefit of VPN is that it is an ideal way to handle mobile users.

VPN