CCNA-2-CHAPTER-1.docx

CCNA 2 CHAPTER 1 CCNA 2 CHAPTER 1 ROUTER

ROUTER

Router - connects one network to a

Router - connects one network to a nother network.nother network. - The router is responsible for the delivery of - The router is responsible for the delivery of packets across different networks.

packets across different networks.

- uses routing table: to determine the best path - uses routing table: to determine the best path toto use to forward a packet

use to forward a packet

- if different IP networks, router forwards packets to - if different IP networks, router forwards packets to the default gateway.

the default gateway.

CHARACTERISTICS OF A NETWORK CHARACTERISTICS OF A NETWORK   TopologyTopology   SpeedSpeed   CostCost   SecuritySecurity   AvailabilityAvailability   ScalabilityScalability   ReliabilityReliability

ROUTERS ARE COMPUTERS ROUTERS ARE COMPUTERS

Cisco IOS (Internetwork Operating System) Cisco IOS (Internetwork Operating System)  – – operating system of cisco routers.

operating system of cisco routers. ROUTER MEMORY

ROUTER MEMORY



 Volatile Memory –Volatile Memory – temporary storage temporary storage 

 Random Access Memory (RAM)Random Access Memory (RAM) - Running IOS

- Running IOS

- Running configuration file - Running configuration file - IP routing and ARP tables - IP routing and ARP tables - Packet buffer

- Packet buffer



 Non-volatile Memory –Non-volatile Memory – permanent storage permanent storage 

 Read-only memory (ROM)Read-only memory (ROM) - Bootup instructions - Bootup instructions - Basic diagnostic software - Basic diagnostic software

- Limited IOS in case the router cannot - Limited IOS in case the router cannot load the full featured IOS

load the full featured IOS 

 Non-Volatile Random Access MemoryNon-Volatile Random Access Memory (NVRAM)

(NVRAM)

- Startup configuration file - Startup configuration file 

 FlashFlash - IOS - IOS

- Other system-related files - Other system-related files

PRIMARY FUNCTIONS OF A ROUTER PRIMARY FUNCTIONS OF A ROUTER



 Determine the best path to send packetsDetermine the best path to send packets 

 Forward packets toward their destinationForward packets toward their destination PACKET FORWARDING MECHANISMS

PACKET FORWARDING MECHANISMS 

 Process switching - each packet Process switching - each packet must bemust be processed by the CPU individually. processed by the CPU individually. 

 Fast switching - first packet of a flow isFast switching - first packet of a flow is process-switched and added to the process-switched and added to the fast-switching cache.

switching cache. 

 Cisco Express Forwarding (CEF) - builds theCisco Express Forwarding (CEF) - builds the FIB and adjacency tables. Preferred

FIB and adjacency tables. Preferred mechanism for cisco routers. mechanism for cisco routers. DEFAULT GATEWAY

DEFAULT GATEWAY

-- if sending packets is of if sending packets is of the same network:the same network: packet is sent from host interface

packet is sent from host interface -- if different networks: packet is sent toif different networks: packet is sent to

default gateway default gateway



 IP addressIP address- Identifies a unique host on a- Identifies a unique host on a local network.

local network. 

 Subnet maskSubnet mask - Identifies with which- Identifies with which network subnet the host can

network subnet the host can communicate.

communicate. 

 Default gatewayDefault gateway - Identifies the IP address- Identifies the IP address of the router to send a pack

of the router to send a pack et to when theet to when the destination is not on the same local

destination is not on the same local network subnet.

network subnet.

- also used to connect - also used to connect local network to internet

local network to internet

Gateway of last resort

Gateway of last resort- A router is also usually- A router is also usually configured with its own default gateway. configured with its own default gateway.

DOCUMENT NETWORK ASSIGNING DOCUMENT NETWORK ASSIGNING



 Topology diagramTopology diagram - Provides a visual- Provides a visual reference that indicates the physical reference that indicates the physical connectivity and logical Layer 3

connectivity and logical Layer 3 addressing.addressing. Often created using software, such as Often created using software, such as Microsoft Visio.



 An addressing tableAn addressing table- A table that captures- A table that captures device names, interfaces, IPv4 a

device names, interfaces, IPv4 a ddresses,ddresses, subnet masks, and default gateway subnet masks, and default gateway addresses.

addresses.

ENABLE IP ON HOST ENABLE IP ON HOST

Statically

Statically - manually assigned IP - manually assigned IP

- used to identify specific network - used to identify specific network resources such as servers/printers.

resources such as servers/printers. - can be used in

- can be used in small networks with littlesmall networks with little number of hosts.

number of hosts. Dynamically

Dynamically - automatically obtained IP address. IP - automatically obtained IP address. IP address from DHCP Server

address from DHCP Server

DEVICE LEDs DEVICE LEDs

-- Indicates the status of the routerIndicates the status of the router -- green led green led : good connections: good connections

-- blinking led blinking led : denotes network activity: denotes network activity



 1 blink + pause –1 blink + pause – port operating at 10 Mb/s port operating at 10 Mb/s 

 2 blink + pause –2 blink + pause – port operating at 100 port operating at 100 Mb/s

Mb/s 

 1 blink + pause –1 blink + pause – port operating at 1000 port operating at 1000 Mb/s

Mb/s

CONSOLE ACCESS CONSOLE ACCESS

-- required when initially configuring a device,required when initially configuring a device, or if remote access (SSH and HTTP) fails. or if remote access (SSH and HTTP) fails.

Console cable

Console cable - RJ-45-to-DB-9 serial cable or a USB- RJ-45-to-DB-9 serial cable or a USB serial cable

serial cable

Terminal emulation software

Terminal emulation software- Tera Term, PuTTY,- Tera Term, PuTTY, HyperTerminal

HyperTerminal

ENABLE IP ON SWITCH ENABLE IP ON SWITCH

- IP addressed is configured virtually via

- IP addressed is configured virtually via

switched virtual interface (SVI)

switched virtual interface (SVI)



 Name the deviceName the device



 Secure management accessSecure management access



 Configure a bannerConfigure a banner

copy run start

copy run start – – to save changes in a router to save changes in a router CONFIGURE IPv4 ROUTER INTERFACE CONFIGURE IPv4 ROUTER INTERFACE

- configure IP address and subnet mask - configure IP address and subnet mask - no shutdown: to enable interface - no shutdown: to enable interface

- clock rate: to configure serial interface CDE - clock rate: to configure serial interface CDE CONFIGURE IPv6 ROUTER INTERFACE

CONFIGURE IPv6 ROUTER INTERFACE

-- same as configuring ipv4 but uses “ipv6” insame as configuring ipv4 but uses “ipv6” in terminal instead of “ip”

terminal instead of “ip”

- still uses no shutdown for activation - still uses no shutdown for activation



 IPv6 supports more than one addressIPv6 supports more than one address - Global unicast address

- Global unicast address - EUI-64: low order bits - EUI-64: low order bits - link local

- link local

CONFIGURE THE LOOPBACK0 INTERFACE CONFIGURE THE LOOPBACK0 INTERFACE

- is a logical

- is a logical interface internal to the router. Itinterface internal to the router. It is not assigned to a physical port.

is not assigned to a physical port. - interface is always up

- interface is always up, no need for “no, no need for “no shutdown”

shutdown”

- used for testing - used for testing

- multiple loopback addresses can be enabled. - multiple loopback addresses can be enabled. VERIFY INTERFACE SETTINGS

VERIFY INTERFACE SETTINGS 

 show ip interface briefshow ip interface brief- Displays a- Displays a summary for all interfaces



 show ip routeshow ip route- Displays the contents of the- Displays the contents of the IPv4 routing table stored in RAM.

IPv4 routing table stored in RAM. 

 show running-config interfaceshow running-config interfaceinterface-id interface-id  --Displays the commands configured on the Displays the commands configured on the specified interface.

specified interface.

For IPv6, commands are also the same with IPv4 For IPv6, commands are also the same with IPv4



 show ipv6 interface brief show ipv6 interface brief  

 show ipv6 routeshow ipv6 route 

 show ipv6 interfaceshow ipv6 interface 

 pingping

FILTER SHOW COMMAND OUTPUT FILTER SHOW COMMAND OUTPUT



 Use the ‘terminal length Use the ‘terminal length <number>’<number>’

command to specify the number of lines to command to specify the number of lines to be displayed.

be displayed. 

 To filter out specific output of commands,To filter out specific output of commands, use the “|” pipe character.

use the “|” pipe character. 

 Can use parameters to filter: section,Can use parameters to filter: section, include, exclude, and begin

include, exclude, and begin show history

show history – – captures last 10 lines in  captures last 10 lines in the historythe history buffer

buffer

ROUTER SWITCHING FUNCTION ROUTER SWITCHING FUNCTION

-- which is the process used by a which is the process used by a router torouter to accept a packet on one interface and accept a packet on one interface and forward it out of another interface. forward it out of another interface. PACKET SWITCHING

PACKET SWITCHING

1.

1. In sending packets from PC 1 to PC 2, theIn sending packets from PC 1 to PC 2, the source IP address is of PC1 and destination source IP address is of PC1 and destination IP address is of PC2.

IP address is of PC2. 2.

2. The IP address does not change in the data,The IP address does not change in the data, instead when forwarded, the MAC address instead when forwarded, the MAC address changes

changes 3.

3. Switch are not considered as destinationSwitch are not considered as destination sources but only routers and end devices. sources but only routers and end devices.

4.

4. If the next hop MAC address is unknown,If the next hop MAC address is unknown, the device issues and ARP request

the device issues and ARP request 5.

5. Routers de-encapsulates the frame andRouters de-encapsulates the frame and determines the destination MAC address determines the destination MAC address from the given IP address.

from the given IP address. ROUTING DECISIONS

ROUTING DECISIONS

The routing table search results in one of

The routing table search results in one of three paththree path determinations:

determinations: 

 Directly connected networkDirectly connected network - If the- If the destination IP address of the packet

destination IP address of the packet belongsbelongs to a device on a network that is directly to a device on a network that is directly connected to one of the interfaces of the connected to one of the interfaces of the router, that packet is forwarded directly to router, that packet is forwarded directly to the destination device.

the destination device. 

 Remote networkRemote network - If the destination IP- If the destination IP address of the packet belongs to a

address of the packet belongs to a remoteremote network, then the packet is forwarded to network, then the packet is forwarded to another router.

another router. 

 No route determinedNo route determined- If the destination IP- If the destination IP address of the packet does not

address of the packet does not belong tobelong to either a connected or remote network, the either a connected or remote network, the router determines if there is a Gateway router determines if there is a Gateway ofof Last Resort available. If there is a default Last Resort available. If there is a default route, the packet is forwarded to

route, the packet is forwarded to thethe Gateway of Last Resort. If the router does Gateway of Last Resort. If the router does not have a default route,

not have a default route, then the packet isthen the packet is discarded.

discarded. BEST PATH

BEST PATH

- the best path to a

- the best path to a network is the path withnetwork is the path with the lowest metric.

the lowest metric.

- metric is the value used to

- metric is the value used to measure themeasure the distance to a given network

distance to a given network 

 Routing Information Protocol (RIP)Routing Information Protocol (RIP)- Hop- Hop count

count 

 Open Shortest Path First (OSPF)Open Shortest Path First (OSPF) -- Cisco’sCisco’s cost based on cumulative bandwidth from cost based on cumulative bandwidth from source to destination

source to destination 

 Enhanced Interior Gateway RoutingEnhanced Interior Gateway Routing Protocol (EIGRP)

Protocol (EIGRP) - Bandwidth, delay, load,- Bandwidth, delay, load, reliability

ADMINISTRATIVE DISTANCE ADMINISTRATIVE DISTANCE

- represents the "trustworthiness" of the - represents the "trustworthiness" of the route; the lower the AD, the more trustworthy the route; the lower the AD, the more trustworthy the route source.

route source.

ROUTING TABLE ROUTING TABLE



 Directly connected routesDirectly connected routes- These routes- These routes come from the active router interfaces. come from the active router interfaces. Routers add a directly connected route Routers add a directly connected route when an interface is configured with an I when an interface is configured with an I PP address and is activated.

address and is activated. 

 Remote routes - These are remoteRemote routes- These are remote networks connected to other routers. networks connected to other routers. Routes to these networks can either be Routes to these networks can either be statically configured or dynamically learned statically configured or dynamically learned through dynamic routing protocols.

through dynamic routing protocols. routing table - is a data file in RAM that is used to routing table - is a data file in RAM that is used to store route information about directly connected store route information about directly connected and remote networks.

and remote networks. ROUTING TABLE SOURCES ROUTING TABLE SOURCES Routing Table Entries: Routing Table Entries:



 Local Route interfacesLocal Route interfaces 

 Directly connected interfacesDirectly connected interfaces – – activated activated with no shutdown

with no shutdown 

 Static routes –Static routes – manually configured manually configured 

 Dynamic routing protocolDynamic routing protocol- dynamic routing- dynamic routing protocols (EIGRP, OSPF)

protocols (EIGRP, OSPF) REMOTE NETWORK ROUTING ENTRIES REMOTE NETWORK ROUTING ENTRIES



 Route source - Identifies how the route wasRoute source- Identifies how the route was learned.

learned.



 Destination networkDestination network- Identifies the- Identifies the address of the remote network. address of the remote network. 

 Administrative distanceAdministrative distance- Identifies the- Identifies the trustworthiness of the route source. trustworthiness of the route source. LowerLower values indicate preferred route source. values indicate preferred route source. 

 MetricMetric- Identifies the value assigned to- Identifies the value assigned to reach the remote network. Lower values reach the remote network. Lower values indicate preferred routes.

indicate preferred routes. 

 Next-hopNext-hop - Identifies the IPv4 address of - Identifies the IPv4 address of thethe next router to forward the packet to.

next router to forward the packet to. 

 Route timestampRoute timestamp- Identifies how much- Identifies how much time has passed since the route was time has passed since the route was learned.

learned. 

 Outgoing interfaceOutgoing interface - Identifies the exit- Identifies the exit interface to use to forward a packet toward interface to use to forward a packet toward the final destination.

the final destination.

DIRECTLY CONNECTED INTERFACES DIRECTLY CONNECTED INTERFACES

- considered up when: - considered up when:

1. assigned valid IP address 1. assigned valid IP address 2. no shutdown command 2. no shutdown command

3. receive carrier signal from other 3. receive carrier signal from other devices (switch, router, host)

devices (switch, router, host)

DIRECTLY CONNECTED ROUTING TABLE ENTRIES DIRECTLY CONNECTED ROUTING TABLE ENTRIES



 Route sourceRoute source - Identifies how the route was- Identifies how the route was learned. Directly connected interfaces have learned. Directly connected interfaces have two route source codes. ‘

two route source codes. ‘CC’ identifies a’ identifies a directly connected network. ’

directly connected network. ’ LL’ identifies’ identifies the IPv4 address assigned to the router’s the IPv4 address assigned to the router’s interface.

interface. 

 Destination networkDestination network- The address of the- The address of the remote network.



 Outgoing interfaceOutgoing interface- Identifies the exit- Identifies the exit interface to use when forwarding packets to interface to use when forwarding packets to the destination network.

the destination network.

STATIC ROUTES STATIC ROUTES

- added after directly connected interfaces are - added after directly connected interfaces are added

added

- are manually configured. Benefits are - are manually configured. Benefits are improved security and resource efficiency improved security and resource efficiency

- disadvantage: lack of automatic - disadvantage: lack of automatic configuration when topology changes. configuration when topology changes. Two types of Static Routes:

Two types of Static Routes:

1. Static route to a specific network 1. Static route to a specific network

Router(config)#

Router(config)#ip routeip route networknetwork

mask

mask{{next-hop-ipnext-hop-ip | | exit-intf exit-intf  } }

2. Default static route 2. Default static route

Router(config)#

Router(config)#ip route 0.0.0.0ip route 0.0.0.0 0.0.0.0

0.0.0.0 { {exit-intf exit-intf  | | next-hop-ipnext-hop-ip } }

DYNAMIC ROUTING DYNAMIC ROUTING

- Dynamic routing protocols are used by - Dynamic routing protocols are used by routers to share information about the reachability routers to share information about the reachability and status of remote networks.

and status of remote networks.

- automatically share routing information with - automatically share routing information with other routers and compensate for any topology other routers and compensate for any topology changes without involving the network

changes without involving the network administrator.

administrator.

Dynamic IPv4 routing protocols supported by Cisco Dynamic IPv4 routing protocols supported by Cisco



 EIGRPEIGRP - Enhanced Interior Gateway Routing- Enhanced Interior Gateway Routing Protocol

Protocol 

 OSPFOSPF - Open Shortest Path First- Open Shortest Path First 

 IS-ISIS-IS - Intermediate System-to-Intermediate- Intermediate System-to-Intermediate System

System 

 RIPRIP- Routing Information Protocol- Routing Information Protocol

Dynamic IPv6 routing protocols supported by Cisco Dynamic IPv6 routing protocols supported by Cisco



 RIPng (RIP next generation)RIPng (RIP next generation)



 OSPFv3OSPFv3

