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
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
18.
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
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 ]
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
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.
