Overloading NAT with Port Address Translation

As mentioned earlier, NAT is one of the key features that helped to reduce the speed at which the IPv4 address space was being depleted. NAT overloading, also known as Port Address Translation (PAT), is the NAT feature that actually provides the significant savings of IP addresses. The key to understanding how PAT works is to consider the following: From a server’s perspective, there is no significant difference between 100 different TCP connections, each from a different h..

Maintaining the Topology Table

The topology table may be recalculated because a new network is added to the network, successors change, or because a network is lost. Figure 3-4 illustrates the traffic flow seen when a router loses a connection.  Figure 3-4. Traffic Flow Used to Maintain the Topology Table Just as the neighbor table tracks the receipt of the EIGRP packets, the topology table records the packets that have been sent by the router to the neighbors. It also identifies the status of the ..

Single CPU Designs

The first approach utilizes a single CPU-controlled shared bus that connects a number of slave interface cards. This arrangement can be based on a general-purpose computer, such as a PC running UNIX or Windows NT. Various bus communication strategies (such as shared memory, DMA, and bus mastering), together with high-performance RISC CPUs, can result in a router of significant forwarding capabilities.   A large number of dedicated-purpose centralized CPU router pl..

The Need for Queuing on Frame Relay Networks

Modern Frame Relay networks service a mixed variety of traffic types from users. Among the different types of traffic, mission-critical and delay-sensitive traffic are extremely susceptible to network latency. For example, delay-sensitive traffic, such as voice, is intolerant to network latency and delay largely because of the nature of the application. Network latency and delay could cause voice packets to be delayed, lost, or arrive out of order. This can severely impact th..

Defining DHCP Configuration Options

You can configure a wide variety of DHCP parameters for configuring client workstations: Router1#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Router1(config)#ip dhcp pool ORAserver Router1(dhcp-config)#host 172.25.1.34 255.255.255.0 Router1(dhcp-config)#client-name bigserver Router1(dhcp-config)#default-router 172.25.1.1 172.25.1.3 Router1(dhcp-config)#domain-name oreilly.com Router1(dhcp-config)#dns-server 172.25.1.1 10.1.2.3..