Router configuration involves configuring the components of a router like RAM, NVRAM, flash memory, interfaces, and ROM. RAM stores routing tables and caches. NVRAM stores the startup configuration. Flash memory stores the IOS image. Interfaces connect routers to networks. Dynamic routing protocols like RIP, IGRP, OSPF, and EIGRP can be configured to exchange routing information. Static routes can also be configured using the ip route command. Troubleshooting commands help monitor router operation and troubleshoot issues.

1. Router Configuration

3. CISCO 2500 series router

5. • 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.

6. 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

7. 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

8. 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)

9. 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

10. 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

14. Console port connections

16. Router Configuration

17. 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

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

20. 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

21. 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

22. 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 ]

23. Routing and Routing Protocols

24. 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

25. Dynamic Routing

26. 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

27. 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

28. 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

29. • RouterA(config) #router igrp as-number

30. More on Routing…
• OSPF and EIGRP
• EGP and IGP
• Switching
• VLAN
• Access Control List (ACL)

31. 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

32. 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

33. 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.