Router Configuration

CISCO 2500 series router

• A router is a special type of computer. It has the same basic components as a standard desktop PC. It has a CPU, memory, a system bus, and various input/output interfaces.

Router Components: RAM

RAM has the following characteristics and functions: • Stores routing tables • Holds ARP cache • Holds fast-switching cache • Performs packet buffering as shared RAM • Maintains packet-hold queues • Provides temporary memory for the configuration file of a

router while the router is powered on • Loses content when a router is powered down or

restarted

Router Components: NVRAM

NVRAM has the following characteristics and functions:

• Provides storage for the startup configuration file

• Retains content when a router is powered down or restarted

Router Components: Flash memory

Flash memory has the following characteristics and functions:

• Holds the IOS image • Allows software to be updated without removing

and replacing chips on the processor • Retains content when a router is powered down

or restarted • Can store multiple versions of IOS software • Is a type of electrically erasable programmable

read-only memory (EEPROM)

Router Components: ROM

ROM has the following characteristics and functions:

• Maintains instructions for power-on self test (POST) diagnostics

• Stores bootstrap program and basic operating system software

• Requires replacing pluggable chips on the motherboard for software upgrades

Router Components: Interfaces

Interfaces have the following characteristics and functions:

• Connect routers to a network for packet entry and exit

• Can be on the motherboard or on a separate module

Console port connections

Router Configuration

Cisco IOS Software

• Basic routing and switching functions

• Reliable and secure access to networked resources

• Network scalability

Router> show version …<output omitted>… cisco 2620 (MPC860) processor (revision 0x102) with 59392K/6144K bytes of memory

Router>show flash

Router# configure terminal Router(config)# • Type exit or Ctrl-Z to returnRouter(config)#hostname Tokyo Tokyo(config)# Router(config)#line console 0 Router(config-line)#login Router(config-line)#password <password >

show commands• show ? – any time for help with commands type ?• Router# show interfaces serial 0/1

• show clock - Shows the time set in the router • show hosts - Displays a cached list of host names and

addresses • show users - Displays all users who are connected to the

router • show history - Displays a history of commands • show flash - information about flash memory and IOS

files • show version - currently loaded software version and

hardware • show protocols - status of configured Layer 3 protocols • show startup-config - saved configuration located in

NVRAM • show running-config

Configuring interfaces

• Router(config)#interface serial 0/0 • Router(config-if)# ip address <ip address > <netmask > • Router(config)#interface serial 0/0 • Router(config-if)#clock rate 56000 • Router(config-if)#no shutdown

• Router#copy running-config startup-config • Router#erase startup-config

Routing and Routing Protocols

• dynamic routing, • static routing

– ip route command to manually configure a static route.

– administrative distance is an optional parameter that indicates the reliability of a route.

– waycross(config)# ip route 172.16.3.0 255.255.255.0 172.16.4.1 130

– Route can be configure by outgoing interface or next hop ip address.

– default route is given by ip route 0.0.0.0 0.0.0.0 [next-hop-address | outgoing interface ]

Routing and Routing Protocols

Dynamic Routing

Two types of dynamic routing:• Distance vector • Link-state

routing protocols:• Routing Information Protocol (RIP) • Interior Gateway Routing Protocol (IGRP) • Enhanced Interior Gateway Routing Protocol (EIGRP) • Open Shortest Path First (OSPF)

routed protocols :• Internet Protocol (IP) • Internetwork Packet Exchange (IPX)

• Autonomous systems - 16-bit identification number – Routing protocols, e.g. Cisco IGRP, require assignment of a unique AS

Dynamic Routing

Configuring Dynamic Routing

• BHM(config) #router rip – Selects RIP as the routing protocol

• BHM(config-router) #network 10.0.0.0 – Specifies a directly connected network

• BHM(config-router) # network 192.168.13.0 – Specifies a directly connected network

• RIP was originally specified in RFC 1058 :– It is a distance vector routing protocol.– Hop count is used as the metric for path selection.– If the hop count is greater than 15, the packet is discarded.– Routing updates are broadcast every 30 seconds, by default.– Load balancing among multiple equidistance path

Troubleshooting

• ABC#show ip protocols • ABC#show ip route • ABC#show interface interface• ABC#show ip interface interface• ABC#show running-config

• show ip rip database• show ip protocols {summary}• debug ip rip {events}• ip interface brief

IGRP

• IGRP uses the following metrics:– Bandwidth – The lowest bandwidth value in

the path– Delay – The cumulative interface delay along

the path– Reliability – The reliability on the link toward

the destination as determined by the exchange of keepalives

– Load – The load

• RouterA(config) #router igrp as-number

More on Routing…

• OSPF and EIGRP

• EGP and IGP

• Switching

• VLAN

• Access Control List (ACL)

OSPF

• OSPF is a nonproprietary link-state routing protocol.– It is a link-state routing protocol.– It is an open standard routing protocol described in

RFC 2328.– The SPF algorithm is used to calculate the lowest

cost to a destination.– Routing updates are flooded as topology changes

occur.# router ospf process-id # network net-address wildcard-mask area area-id

EIGRP

• EIGRP is a Cisco proprietary enhanced distance vector routing protocol.– It is an enhanced distance vector routing protocol.– It uses unequal cost load balancing.– It uses a combination of distance vector and link-state features

(hybrid).– It uses Diffused Update Algorithm (DUAL) to calculate the

shortest path.– Routing updates are multicast using 224.0.0.10 triggered by

topology changes. Max hop 255

RA(config-router)# router eigrp autonomous-system-number

RA(config-router)# network network-number

BGP

• Border Gateway Protocol (BGP) is an exterior routing protocol.– It is a distance vector exterior routing protocol.– It is used between ISPs or ISPs and clients.– It is used to route Internet traffic between

autonomous systems.