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.

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

VPLS

• Enables carriers to bring various WAN connections (IP or MPLS) together in a single logical ethernet network
• Allows MPLS networks to provide multipoint ethernet services
• Allow CE nodes to communicate directly with other CE nodes
• Ethernet Bridges – Pseudo-Wires (PW)
• Forwards frames at L2
• Self-learn source MAC address to port and frames are forwarded based on destination MAC address
  • If MAC is unknown, broadcast or multicast is flooded out all ports associated with virtual bridge
• Architecture must perform
  • Auto discover other PE’s associated with the VPLS instance
  • Signaling of PWs to interconnect VPLS virtual Switch Instance (VSI)
  • Loop avoidance
  • MAC address withdrawal

Metro-Ethernet

• • Separated into different subsections
  • Port-based
  • Per-vlan
  • Per-class per-vlan

Point-to-point

Simple:

Ethernet private line (EPL) (for example, Ethernet mapped to SONET/SDH frames) or Ethernet Internet access with IPsec encryption (no split tunnel)

Trunked:

Ethernet Virtual Private Line (EVPL), also called Ethernet Relay Service (ERS)

 

Multipoint

Simple:

Ethernet Internet access with multipoint DMVPN or MPLS Ethernet access to group encrypted transport (GET)

Trunked:

Ethernet Relay Multipoint Service (ERMS) or Ethernet Multipoint Service (EMS)

 

 

Carrier Ethernet Services

• Ethernet Virtual Private Line – E-LINE

  • Connect 2 customer ethernet ports over a WAN
  • Ethernet Private Line (EPL)
    • Provide p2p ethernet virtual connection (EVC) between a pair of user network interfaces (UNIs)
    • High degree of transparency
  • ○ Ethernet Virtual Private Line (EVPL)
    • Provide p2p or p2m between a pair of UNIs

• Ethernet Virtual Private LAN – E-LAN

  • Multipoint service connecting sets of customer endpoints
  • Appearance of a bridged ethernet connecting the sites

• Ethernet Virtual Private Tree – E-TREE

  • Multipoint service connecting one or more root to a set of leaves