CCIE – RS – L3 Technologies – Addressing Technologies – IPv4

In this section I assume that you have a CCNA level of understanding of IP addressing

Identify, Implement and Troubleshoot IPv4 Addressing and Subnetting


Address Types

Class A:

0.0.0.0 to 127.255.255.255

Private range: 10.0.0.0 – 10.255.255.255

Class B:

128.1.0.0 to 191.255.255.255

Private range: 172.16.0.0 to 172.32.255.255

Class C:

192.0.1.1 to 223.255.254.255

Private range: 192.168.0.0 to 192.168.255.255

Class D:

224.0.0.0 to 239.255.255.255

Class E:

240.0.0.0 to 254.255.255.255.255


VLSM

Variable Length Subnet Mask

Allows for dividing ip addresses into subnets of different sizes

I make the following table before doing any subnetting math. This will help you figure out what the /cidr into subnet mask numbers will be without much effort. This will then help you figure out the network and broadcast range.

Screen Shot 2018-01-28 at 8.33.15 PM.png

Subnet Math: What are the network and broadcast addresses of the following range

192.168.12.0/28

/28 = 255.255.255.240

Network – 192.168.12.0, Broadcast 192.168.12.15

172.27.25.0/19

/19 = 255.255.224.0

Network – 172.27.0.0, Broadcast 172.27.31.255


ARP

Address Resolution Protocol

  • RFC 826
  • Protocol so that IP hosts can discover the MAC address of another device
  • L3 needs ARP to map IP network addresses to MAC hardware addresses so IP packets can be sent across networks
  • Cisco routers hold ARP entries for 4 hours by default
    • This can be changed under interface configuration: arp timeout ###

Proxy ARP

  • Allow L3 device to respond on behalf of actual destination for ARP
  • RFC 925 and 1027
  • Router makes itself available to hosts as a “gateway”
    • If a host is missing it’s default gateway the router will act as this
  • Enabled by default: disable on interface with – no ip proxy-arp

Reverse ARP (RARP)

  • Host attempting to find its own IP address, replaced DHCP
  • Maps IP address to known hardware address

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