User:Itpastorn/dko/ccna1-3.1-10
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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
Routed Protocol
[edit]Routable and routed protocols
[edit]Examples of routable protocols
- IP
- IPX
- AppleTalk
- DECnet
- Banyan VINES
- Xerox Network Systems (XNS).
IP as a routed protocol
[edit]Packet propagation and switching within a router
[edit]Connectionless and connection-oriented delivery
[edit]- Packet propagation within a router
Anatomy of an IP packet
[edit]- 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
Routed vz. Routing
[edit]Path determination
[edit]- 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
- Bandwidth
- Delay
- Load
- Reliability
- Hop count
- Ticks (Approximately 1/18 second)
- Cost
Link state and distance vector
[edit]Mechanics of subnetting
[edit]Classes of network IP addresses
[edit]| 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) |
Introduction to and reason for subnetting
[edit]- 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.
Establishing the subnet mask address
[edit]- Number of usable host addresses
- Requirement of the largest subnet
Applying the subnet mask
[edit]- Classic (dotted) notation
- CIDR notation