(Week 2) - Lesson 4D - Configure Private and Public IPv4Addressing Schemes

Private Addressing

(internal) addresses are not routed on the Internet and no traffic can be sent to them from the Internet, they only supposed to work within the local network.

Variable Length Subnet Masking (VLSM)

A scheme to maximize IP Address space capacity through use of different size subnet masks within the same IP Network

Network Address Translation (NAT)

A simple form of Internet security that conceals internal addressing schemes from the public Internet by translating between a single public address on the external side of a router and private, non-routable addresses internally.

Public IP Network

Any IPv4 Class A, B, or C network assigned for use by one organization only, so that the addresses in the network are unique across the Internet, allowing packets to be sent through the public Internet using the addresses. The allocation is governed by IANA and administered by regional registries and ISPs

True or False? The IP address 172.24.0.1 is routable over the Internet.

False. 172.16.0.0 - 172.31.255.255 is the Class B private address range.

What two methods can an organization use to facilitate Internet access for hosts configured with private addresses?

One method is to use Network Address Translation (NAT) and a router configured with one or more public addresses. NAT allows the router to translate between the two schemes. The second option is to use a proxy server with a public IP address. The proxy fulfils requests on behalf of the LAN clients and forwards responses back to them.

A company has four networks, using the addresses 192.168.0.0/24, 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24. What network prefix and subnet mask can be used to summarize a supernet route to these networks?

The network prefix is /22 and the mask is 255.255.252.0.

Loopback Address

The range 127.0.0.0 to 127.255.255.255 (or 127.0.0.0/8) is reserved. This range is used to configure a loopback address, which is a special address typically used to check that TCP/IP is correctly installed on the local host. Every IP host is automatically configured with a default loopback address, typically 127.0.0.1.

What is the significance of the address 127.0.0.1?

This is the default loopback address for most hosts. The loopback address facilitates testing the TCP/IP implementation on a host.

True or False? VLSM means using more than one mask to subnet an IP network.

True. By using different mask sizes, variable length subnet masking (VLSM) allows designers to match subnet sizes to requirements more precisely

169.254.0.0 to 169.254.255.255

Used by hosts for automatic Private IP Addressing (APIPIA or Link-Local Addressing)

255.255.255.255

Used to broadcast to the local network when the local network address is not known.

0.0.0.0/8

Used when a specific address is unknown. This is typically used as a source address by a client seeking a DHCP lease.

Classless Inter-Domain Routing (CIDR)

Using network prefixes to aggregate routes to multiple network blocks ("supernetting"). This replaced the old method of assigning class-based IP addresses based on the network size.

Private IP addresses can be drawn from one of the pools of addresses defined in RFC 1918 as non-routable over the Internet:

• 10.0.0.0 to 10.255.255.255 (Class A private address range). • 172.16.0.0 to 172.31.255.255 (Class B private address range). • 192.168.0.0 to 192.168.255.255 (Class C private address range).