User:Itpastorn/dko/ccna1-3.1-10

Module 10 Routing Fundamentals and Subnets

Overview CCNA 1 - Module 10 (3.1)

• Routed vz routing vz unrouted Protocols
• Data encapsulation, as data is routed
• Connectionless and connection-oriented
• The IP packet fields
• How data is routed, routing metrics
• Compare and contrast different types of routing protocols
• Metrics used by routing protocols
• Uses for subnetting
• Calculate subnet masks
• Calculate subnet ID

Examples of routable protocols

• IP
• IPX
• AppleTalk
• DECnet
• Banyan VINES
• Xerox Network Systems (XNS).

• Packet propagation within a router

• Anatomy of an IPv4 packet
• Anatomy of an IPv6 packet

• Provides processes used to share route information
• Allows routers to communicate with other routers to update and maintain the routing tables

"A router is a network layer device that uses one or more routing metrics to determine the optimal path along which network traffic should be forwarded."

Non-routable protocols have no layer 3 functionality. E.g. NetBEUI.

Layer 3 vz. layer 2 (long distance vz. local calls)

Both have:

• ARP-tables

The switch:

• Uses MAC-addresses
• Has CAM-tables
• Forwards broadcasts

The router:

• Uses IP-addresses
• Has routing tables
• Blocks broadcasts

• Compares the IP address of the packet to the IP tables
  • Obtained destination address from the packet.
  • Apply mask of first entry and compare
  • Forward if its a match
  • Otherwise repeat process for next entry in the table
• No match at all?
  • Default route?
  • Yes. Use it!
• No default route? The packet is discarded. (Perhaps) tell sender that destination is unreachable.

"A hierarchical address scheme is required for data transfers."

• Protocol type
• Next-hop associations
• Routing metric
• Outbound interfaces

Design goals:

• Optimization – "Select the best route" based on metrics.
• Simplicity and low overhead – Simple algorithm = easy to process
• Robustness and stability – can handle unusual or unforeseen circumstances
• Flexibility – Adapt quickly to a changes
• Rapid convergence - all routers should "agree" quickly

routing metrics

• Bandwidth
• Delay
• Load
• Reliability
• Hop count
• Ticks (Approximately 1/18 second)
• Cost

• IGP:
  • RIP
  • RIPv2
  • IGRP
  • EIGRP
  • OSPF
  • Intermediate System-to-Intermediate System (IS-IS) protocol
• EGP:
  • • BGP

• Distance-vector routing protocol
  • Path vector protocol
• Link-state routing protocol

A-class	B-class	C-class	D-class
8 network bits 24 host bits	16 network bits 16 host bits	24 network bits 8 host bits	32 host bits
16.7 million hots	65 534 hosts	254 hosts	(used exclusively for multicasting groups)

• Manageability
• Broadcast containment
• Low-level security (routers as firewalls between subnets)

Subnets are not seen from outside. Traffic to all subnets may be directed to the net as a whole.

IPv4 subnetting reference

• Number of usable host addresses
  • Requirement of the largest subnet

• Classic (dotted) notation
• CIDR notation

• How the Internet Layer Works at Learn Networking
• How to Subnet a Network at Learn Networking

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