Review Notes, v. 3.1
1.1.1 Private addressing

1.1.2 Major NAT and PAT features
Dynamic NAT is designed to map a private IP address to a public address. Any IP address from a pool of public IP addresses is assigned to a network host. Overloading, or Port Address Translation (PAT), maps multiple private IP addresses to a single public IP address. Multiple addresses can be mapped to a single address because each private address is tracked by a port number.
1.1.3 Configuring NAT and PAT
The access list must permit only those addresses that are to be translated. Remember that there is an implicit deny all at the end of each access list.

1.1.4 Configuring DHCP
- Typically, a DHCP server will be configured to assign much more than an IP address. Other IP configuration values such as the default gateway can be set from the DHCP configuration mode. Using the default-router command sets the default gateway.
- A default router must be defined for clients
2.1.1 WAN devices
- For digital lines, a channel service unit (CSU) and a data service unit (DSU) are required. The two are often combined into a single piece of equipment, called the CSU/DSU. The CSU/DSU may also be built into the interface card in the router.
- A modem is needed if the local loop is analog rather than digital.
- A router is commonly considered a DTE device.
2.1.2 WAN Standards
WANs use the OSI reference model, but focus mainly on Layer 1 and Layer 2.
2.2.1 ISDN
- Another common application of ISDN is to provide additional capacity as needed on a leased line connection.
- ISDN is also used as a backup in the case of a failure of the leased line.

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source: CCNA4: Final Exam