CCNA Guide to Cisco Networking Chapter 8: Routing Protocols and Network Address Translation.

CCNA Guide to Cisco Networking

Chapter 8: Routing Protocols and Network Address Translation


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Objectives

• Understand the purpose and operation of network address translation (NAT)

• Configure static NAT, dynamic NAT, and dynamic NAT with overload

• Understand and configure port address translation (PAT)

• Differentiate between nonroutable, routed, and routing protocols

• Define Interior Gateway Protocols, Exterior Gateway Protocols, distance-vector routing protocols, and link-state routing protocols


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Objectives (continued)

• Explain the concepts of count-to-infinity, split horizon, split horizon with poison reverse, and hold-down timers

• Describe, configure, and monitor the interior routing protocols RIP and IGRP

• Explain static routing and administrative distance

• Configure static routing and default routes


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Network Address Translation

• Static NAT

• Dynamic NAT

• Port Address Translation

• Dynamic Nat with overload

• Overlapping


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Network Address Translation (continued)


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Configuring Network Address Translation

• Configure static NAT– Define static mapping between the inside address

and the outside address– Define the router’s interfaces as inside or outside

• Basic NAT interface assignment– RouterA(config)# int fa 0/0– RouterA(config-if)# ip nat inside– RouterA(config-if)# int serial 0/1– RouterA(config-if)# ip nat outside


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Configuring Dynamic NAT

• Configure a standard access control list to define what internal traffic will be translated

• Define a pool of addresses to be used for dynamic NAT allocation

• Link the access list to the NAT pool

• Define interfaces as either inside or outside


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Configuring Dynamic NAT (continued)

• Dynamic NAT router configurations– RouterA(config)# access-list 1 permit 192.168.0.0

0.0.0.255– RouterA(config)# ip nat pool PoolExample

209.86.192.200 209.86.192.240 netmask 255.255.255.0– RouterA(config)# ip nat inside source list 1 pool

PoolExample– RouterA(config)# int fa 0/0– RouterA(config-if)# ip nat inside– RouterA(config-if)# int serial 0/1– RouterA(config-if)# ip nat outside


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Configuring Port Address Translation To An Outside

Interface

• Configure PAT router commands– Configure a standard access list to define

what internal traffic will be translated– Link the access list to the interface to be used

for PAT– Define interfaces as either inside or outside


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Interface (continued)• PAT router commands

– RouterA(config)# access-list 1 permit 192.168.0.0 0.0.0.255

– RouterA(config)# ip nat inside source list 1 interface serial 0/1 overload

– RouterA(config)# interface serial 0/1– RouterA(config-if)# ip nat outside– RouterA(config-if)# interface fa 0/0– RouterA(config-if)# ip nat inside


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Interface (continued)


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Configuring Dynamic NAT With Overload

• Dynamic NAT with overload is a mixture of dynamic NAT and PAT– Dynamic NAT: Pool of inside addresses to a

small pool of outside addresses– PAT: Same pool of inside addresses to an

single outside address– PAT function becomes available when pool of

outside addresses are all in use

• Use dynamic NAT and PAT configurations using the same pool of inside addresses


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Nonroutable Protocols

• Peer-to-peer networks

• Microsoft Windows operation systems– NetBIOS Enhanced User Interface (NetBEUI)

• Very small• Fast• Efficient• Cannot scale


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Nonroutable Protocols (continued)


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Routed Protocols

• Routed protocols

• Support networks

• Logical addresses

• Transmission Control Protocol/Internet Protocol (TCP/IP)

• Internetwork Packet Exchange/Sequence Packet Exchange (IPX/SPX)


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Routed Protocols (continued)


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Routing Protocols

• Path determination• Routing tables

– Metric– Autonomous system (AS)– Convergence

• Interior gateway protocols (IGP)– Routing information protocol (RIP)– Interior gateway routing protocol (IGRP)– Enhanced Interior gateway routing protocol (EIGRP)– Open shortest path first (OSPF)

• Exterior gateway protocols (EGP)– Border gateway protocol (BGP)


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Routing Protocols (continued)


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Routing Protocols (continued)


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Two Types Of IGPs

• Distant vector and link-state

• Distant-vector– Routing by rumor– Routing loops– Count-to-infinity– Split horizon– Split horizon with poison reverse– Hold-down timers


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Two Types Of IGPs (continued)

• Link-state– Link-state advertisements (LSA)– Shortest path first (SPF) algorithm – Link-state packets

• Common view of the topology– Floods or multicasts LSPs– Triggered updates


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Routing Information Protocol

• RIP has the following attributes– Distance-vector routing protocol– Maximum hop count of 15– 16 hops is considered infinity– Hop count is the only metric available for path

selection– Broadcasts the entire routing table to neighbors every

30 seconds– Capable of load balancing– Easy to configure


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Enabling RIP Routing


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Enabling RIP Routing (continued)


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Configuring RIP Routing For Each Major Network

• Design the network for the appropriate networks

• Configure interfaces to be gateways for networks

• Configure routing protocol

• In router mode establish networks to be advertised


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Configuring RIP Routing For Each Major Network (continued)


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Configuring RIP Routing For Each Major Network (continued)


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“show ip protocol” and “debug ip rip” (continued)


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“show ip protocol” and “debug ip rip” (continued)


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“show ip route” Command


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“show ip route” Command (continued)


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“show ip route” Command (continued)


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Interior Gateway Routing Protocol

• Proprietary distance-vector routing protocol

• Supports hop count of 255– 100 is the default hop count

• Supports up to four equal cost paths

• Routing table updates every 90 seconds


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Interior Gateway Routing Protocol (continued)

• IGRP metrics– Hops: Number of routers between source and

destination networks– Load: The load on a link in the path– Bandwidth: The speed of the link (default)– Reliability: Measures reliability with a scale of

0 to 255– Delay: The delay on the medium (default)– MTU: The size of the datagram


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Static Routing

• Adding static routes– Router(config)# ip route [destination

network/destination ip address] [next hop ip address/forwarding interface] [administrative distance]

– RouterD(config)# ip route 172.32.3.0 255.255.255.0 172.32.2.2

• Changing administrative distance– Default administrative distance of a static route is

• 0 if a forwarding interface is configured• 1 if a next hop ip address is configured

– Router(config)# ip route 192.168.5.0 255.255.255.0 192.168.4.2. 150


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Static Routing (continued)


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Configuring A Default Route

• Routing protocols do not behave equally with default routes– Router(config)# ip route 0.0.0.0 0.0.0.0 [next

hop ip address/forwarding interface] [administrative distance]

• Router(config)# ip default-network [forwarding ip address]


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Configuring A Default Route (continued)


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Summary

• NAT is a technology that allows organizations to map valid external addresses to private or unregistered internal addresses

• This allows organizations to maintain a separation between the Internet and the intranet (internal network) while still providing access to the Internet

• Organizations can use NAT to allow many more people to access the Internet by sharing one or more valid public addresses

• PAT allows an organization to map more than one internal private IP address to a public IP address


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Summary (continued)

• Protocols vary in their functions, some protocols are designed to be used in small networks without the need for Network layer addressing

• These protocols are described as nonroutable protocols, the most common nonroutable protocol is NetBEUI

• Other protocols were designed with the ability to move between multiple networks via Network layer addressing

• These protocols are routed protocols, the most common routed protocol suite is TCP/IP


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Summary (continued)

• Protocols must be available that can find the best path throughout an internetwork and relay that information to routers

• Routing protocols serve this function on modern networks

• Routing protocols are classed in two major groups: Interior Gateway Protocols and Exterior Gateway Protocols

• Interior Gateway Protocols are routing protocols that function within a single autonomous system

• Exterior Gateway Protocols function as routing protocols between autonomous systems


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Summary (continued)

• Interior routing protocols are further divided into distance-vector and link-state routing protocols

• These two types of Interior Gateway Protocols use very different methods to determine the best path in an internetwork

• Distance-vector protocols periodically broadcast entire routing tables to neighbor routers

• Link-state protocols multicast link updates to routers in their area upon startup and when network topology changes

• Two common distance-vector IGPs are the Routing Information Protocol and the Interior Gateway Routing Protocol


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Summary (continued)

• RIP is an easy-to-configure routing protocol that uses hop count as its sole metric

• RIP has a hop count limit of 15• RIP uses split horizon, split horizon with

poison reverse, and hold-down timers to help limit routing loops

• RIP can be used on Cisco and non-Cisco routers


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Summary (continued)

• IGRP is also a distance-vector routing protocol with maximum hop count of 255

• IGRP is not limited to using hop count as its sole metric

• IGRP can also use load, bandwidth, reliability, and delay when determining best path

• IGRP uses only bandwidth and delay by default• IGRP is a Cisco proprietary protocol and can

only be used on Cisco routers


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Summary (continued)

• Static routes are used to conserve bandwidth and lower memory and CPU load on a router while still allowing for correct routing table creation

• Static routes give administrators control and flexibility in path selection in a network

CCNA Guide to Cisco Networking Chapter 8: Routing Protocols and Network Address Translation.

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