Download Static Routes

Routing
Eng. Rania Adel
Computer Network Dep.
Outline
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Operating Cisco IOS – ICND1 -> CH: 13
Routing Protocol Concepts -> ICND1 ->
CH:14
Routing – ICND2  CH: 8
Integrated Service Router (ISR)
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The ISR combines features such as routing and
LAN switching functions, security, voice, and
WAN connectivity into a single device.
The Cisco 1841 is a relatively low cost ISR
designed for small to medium-sized businesses
and small enterprise branch offices.
Integrated Service Router (ISR)
System Power LED (SYS-PWR)
System Activity (SYS ACT)
Indicates power is received and
that the internal power supply is
functional. LED is solid green.
A blinking LED indicates the
system is actively transferring
packets.
Integrated Service Router (ISR)
Modular Slot 1 with a High-speed WAN Interface Card
(HWIC):
Modular slots can be used for different types of interfaces.
The HWIC shown here provides serial connectivity over a
wide-area network.
Integrated Service Router (ISR)
Compact Flash Module:
This removable module is used to store the
Cisco IOS and other operating software for
the ISR.
Integrated Service Router (ISR)
Single Slot USB Port:
The USB Flash feature allows users to
store images and configurations and boot
directly via USB Flash memory.
Integrated Service Router (ISR)
Fast Ethernet Ports:
These ports provide 10/100 Mbps connectivity
for local area networks.
Integrated Service Router (ISR)
Console Port:
This port is used to configure the ISR via
a directly connected host.
Integrated Service Router (ISR)
Auxiliary Port:
This port is used to configure the ISR
via a modem connection.
Integrated Service Router (ISR)
Modular Slot 0 with a Four Port Ethernet Switch:
Modular slots can be used for different types of
interfaces.
The four port Ethernet card shown here provides
LAN connectivity to multiple devices.
Cisco Router Components
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Bootstrap
◦ Stored in ROM
◦ Brings up the router during initialization
◦ It will boot the router and then load the IOS.
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POST (power-on self-test)
◦ Stored in ROM
◦ Checks the basic functionality of the router
hardware and determines which interfaces are
present.
Cisco Router Components
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ROM monitor
◦ Stored in ROM
◦ Used for testing and troubleshooting
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Mini-IOS
◦ Called the RXBOOT or boothelper
◦ The mini-IOS is a small IOS in ROM
◦ It can be used to bring up an interface and load a
Cisco IOS into flash memory
Cisco Router Components
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ROM (read-only memory)
◦ Used to start and maintain the router
◦ Holds the POST and the bootstrap program, as well
as the mini-IOS
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RAM (random access memory)
◦ Used to hold packet buffers, ARP cache, routing
tables, and also the software and data structures
that allow the router to function.
◦ Running-config is stored in RAM, and most routers
expand the IOS from flash into RAM upon boot.
Cisco Router Components
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Flash memory
◦ Stores the Cisco IOS by default
◦ Flash memory is not erased when the router is
reloaded
◦ It is EEPROM (electronically erasable programmable
read-only memory)
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NVRAM (nonvolatile RAM)
◦ Used to hold the router and switch configuration
◦ NVRAM is not erased when the router or switch is
reloaded.
Cisco Router Components
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Configuration register
◦ The configuration register is stored in NVRAM
◦ Used to control how the router boots up
◦ By default is set to 0x2102, which tells the router to
load the IOS from flash memory as well as to load
the configuration from NVRAM
The Router Boot Sequence
1- Router performs a POST
2- Bootstrap looks for & loads the Cisco IOS
3- IOS software looks for a valid configuration file
4- Startup-config file (from NVRAM) is loaded
◦ If startup-config file is not found, the router will start
the setup mode
The Router Boot Sequence
The Router Boot Sequence
The Router Boot Sequence
The Router Boot Sequence
Configuration Register
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Register
◦ 16-bit software written into NVRAM
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Configuration Register Bits
◦ 16 bits read 15-0, from left to right
◦ default setting: 0x2102
Register
Bit number
Binary
2
15 14 13 12
0 0 1 0
1
11 10 9 8
0 0 0 1
0
7 6 5 4
0 0 0 0
2
3 2 1 0
0 0 1 0
NOTE: 0x means the digits that follow are in hexadecimal
Configuration Register
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Bit 6 can be used to ignore the NVRAM
contents (This bit is used for password
recovery)
The boot field, which consists of bits 0–3 in
the configuration register, controls the router
boot sequence
Boot Field Meanings
Changing the Configuration
Register
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Force the system into the ROM monitor mode
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Select a boot source & default boot filename
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Enable or disable the Break function
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Set the console terminal baud rate
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Load operating software from ROM
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Enable booting from a TFTP server
Changing the Configuration
Register
Router(config)#config-register 0x2142
Router(config)#^Z
Router#sh ver
Configuration register is 0x2102 (will be
0x2142 at next reload)
Recovering Passwords
1- Boot the router & interrupt the boot sequence by
performing a break
2- Change the configuration register to turn on bit 6
(0x2142)
3- Reload the router
4- Enter the privileged mode
5- Copy the startup-config to running-config
6- Change the password
7- Reset the configuration register to the default value
8- Reload the router
Cisco IOS Programs
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There are two methods to connect a PC to a
network device to perform configuration
and monitoring tasks:
◦ out-of-band management
◦ in-band management.
Cisco IOS Programs
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Out-of-band Management
◦ Out-of-band management requires a computer to be
directly connected to the console port or auxiliary
port (AUX) of the network device being configured.
◦ This type of connection does not require the local
network connections on the device to be active.
◦ Technicians use out-of-band management to initially
configure a network device, because until properly
configured, the device cannot participate in the
network.
Cisco IOS Programs
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Out-of-band Management
◦ Out-of-band management is also useful when the
network connectivity is not functioning correctly and
the device cannot be reached over the network.
◦ Performing out-of-band management tasks requires
a terminal emulation client installed on the PC.
Cisco IOS Programs
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In-band Management
◦ Use in-band management to monitor and make
configuration changes to a network device over a
network connection.
◦ For a computer to connect to the device and perform
in-band management tasks, at least one network
interface on the device must be connected to the
network and be operational.
Cisco IOS Programs
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In-band Management
◦ Either Telnet, HTTP or SSH can be used to access a
Cisco device for in-band management.
◦ A web browser or a Telnet client program can be used
to monitor the network device or make configuration
changes.
Cisco IOS Programs
Cisco IOS Programs
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The Cisco IOS command line interface (CLI) is a
text-based program that enables entering and
executing Cisco IOS commands to configure,
monitor, and maintain Cisco devices.
The Cisco CLI can be used with either in-band or
out-of-band management tasks.
Cisco IOS Programs
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Use CLI commands to alter the configuration of the
device and to display the current status of
processes on the router.
For experienced users, the CLI offers many timesaving features for creating both simple and
complex configurations.
Almost all Cisco networking devices use a similar
CLI.
When the router has completed the power-up
sequence, and the Router> prompt appears, the
CLI can be used to enter Cisco IOS commands.
Cisco IOS Programs
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In addition to the Cisco IOS CLI, other tools are
available to assist in configuring a Cisco router or
ISR.
Security Device Manager (SDM) is a web-based
GUI device management tool.
Unlike CLI, SDM can be used only for in-band
management tasks.
Routing Basics
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A router uses a routing table to determine where
to send packets.
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The routing table contains a set of routes.
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Each route describes which gateway or interface
the router uses to reach a specified network.
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A route has four main components:
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Destination value
Subnet mask
Gateway or interface address
Route cost or metric
Routing Basics
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When a router receives a packet, the router
examines the destination IP address in that
packet to determine where to forward the
packet.
The router then looks for a matching
destination value in the routing table.
Routing Basics
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On a Cisco router, the Cisco IOS command
show ip route displays the routes in the routing
table.
Several types of routes can appear in the
routing table.
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Directly Connected Routes
Static Routes
Dynamically Updated Routes (Dynamic Routes)
Default Route
Routing Basics
IP Routing process
IP Routing process
Routes to Directly Connected Subnets
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A router automatically adds a route to its
routing table for the subnet connected to each
interface
Configuring an Interface
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There are different types of interfaces on a
router.
Serial and Ethernet interfaces are the most
common.
Local network connections use Ethernet
interfaces.
WAN connections require a serial connection
through an ISP.
Configuring an Interface
Configuring an Interface
Secondary IP Addressing
Secondary IP Addressing
ISL and 802.1Q Configuration on
Routers
ISL and 802.1Q Configuration on
Routers
ISL and 802.1Q Configuration on
Routers
Static Routes
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Configuring Static Routes
◦ Enter global configuration mode.
◦ Use the ip route Cisco IOS command to configure
the static route, with the following format.
◦ ip route [destination_network] [subnet_mask]
[gateway_address]
Or
ip route [destination_network] [subnet_mask]
[exit_interface]
Static Routes
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Configuring Static Routes
Static Routes
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Configuring Static Routes
Static Routes
Static Routes
Static Routes
Static Routes
Static Routes
Static Default Routes
Static Default Routes
Classful and Classless Routing
Classful and Classless Routing
Classful and Classless Routing
Classful and Classless Routing
Dynamic Routing
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Dynamic routing is when protocols are used
to find networks and update routing tables on
routers.
Dynamic routing makes it possible to avoid
the time-consuming process of configuring
static routes.
Dynamic routing use more CPU processing
and network bandwidth than static routing
Routing protocol
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A set of messages, rules, and algorithms used by
routers for the overall purpose of learning routes.
This process includes the exchange and analysis of
routing information.
Each router chooses the best route to each subnet
(path selection) and finally places those best routes
in its IP routing table.
Examples include RIP,EIGRP, OSPF, and BGP.
Routed protocol
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A protocol that defines a packet structure and
logical addressing, allowing routers to
forward or route the packets.
Routers forward, or route, packets defined by
routed protocols.
Examples include IP and IPX (a part of the
Novell NetWare protocol model).
Routing Protocol Functions
1. Learn routing information about IP subnets from
other neighboring routers.
2. Advertise routing information about IP subnets to
other neighboring routers.
3. If more than one possible route exists to reach one
subnet, pick the best route based on a metric.
4. If the network topology changes—for example, a link
fails—react by advertising that some routes have
failed, and pick a new currently best route. (This
process is called convergence.)
Routing Protocol Functions
convergence might occur
if the link between R1
and R2 failed. In that
case, R1 should stop
using its old route for
subnet
172.16.3.0/24
(directly through R2),
instead sending packets
to R3.
Interior and Exterior Routing Protocols
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IGP
◦ Interior Gateway Routing Protocol
◦ Exchange routing information between routers in the
same autonomous system AS
◦ Example: RIP, OSPF, and EIGRP
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EGP
◦ Exterior Gateway Routing Protocol
◦ Designed for use between different autonomous
systems
◦ EGP is used to exchange routes between routers in
different autonomous systems
◦ Example: BGP
Autonomous system (AS)
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An AS is an internetwork under the administrative
control of a single organization.
Each AS is identified by a unique AS number
(ASN).
ASNs are controlled and registered on the
Internet.
Interior and Exterior Routing Protocols
Classful Routing Protocols
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Classful routing protocols do not include the
subnet mask with the route advertisement
◦ Within the same network, consistency of the
subnet masks is assumed.
◦ Summary routes are exchanged between foreign
networks.
◦ Examples of classful routing protocols:
 RIP Version 1 (RIPv1)
 IGRP
Classless Routing Protocols
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Classless routing protocols include the subnet
mask with the route advertisement
◦ Classless routing protocols support variablelength subnet masking (VLSM).
◦ Summary routes can be manually controlled
within the network.
◦ Examples of classless routing protocols:
 RIP Version 2 (RIPv2)
 EIGRP
 OSPF
Metric
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Assigns a cost to each available route so that
the most cost-effective path can be chosen
Routing protocols choose the best route to
reach a subnet by choosing the route with the
lowest metric.
Metric
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Each routing protocol uses different metrics.
The metric used by one routing protocol is not
comparable to the metric used by another routing
protocol.
Two routing protocols might choose different paths
to the same destination because they use different
metrics.
For example, RIP chooses the path with the fewest
number of hops, whereas EIGRP chooses the path
based on the highest bandwidth and least delay.
Metric
Metric
Administrative Distance
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It is possible to have more than one routing
protocol enabled on a single router.
Additionally, a network administrator may
choose to configure static routes to a specific
destination.
If a router has two different paths to a
destination based on two different routing
protocols and their metrics, how does the
router know which path to use?
Administrative Distance
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The router uses what is known as the administrative
distance (AD).
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The AD represents the "trustworthiness" of the route.
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The lower the AD, the more the trustworthy the route.
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Integer value from 0 to 255
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0 used for the most trusted
Administrative Distance
Routing Protocols Classes
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Three main branches of routing protocol
algorithms exist for IGP routing protocols:
◦ Distance vector
◦ Link-state
◦ Balanced hybrid
Distance Vector Concepts
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Routers add directly connected subnets to
their routing tables, even without a routing
protocol.
Routers send routing updates out their
interfaces to advertise the routes that this
router already knows. These routes include
directly connected routes, as well as routes
learned from other routers.
Distance Vector Concepts
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Routers listen for routing updates from their
neighbors so that they can learn new routes.
The routing information includes the subnet
number and a metric.
The metric defines how good the route is;
lower metric routes are considered better
routes.
Distance Vector Concepts
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Routers use broadcasts or multicasts to send
routing updates.
If a router learns multiple routes to the same
subnet, it chooses the best route based on
the metric.
Routers send periodic updates and expect to
receive periodic updates from neighboring
routers.
Distance Vector Concepts
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Failure to receive updates from a neighbor in
a timely manner results in the removal of the
routes previously learned from that neighbor.
A router assumes that, for a route advertised
by Router X, the next-hop router in that route
is Router X.
Distance Vector Concepts
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The term distance vector describes what a
router knows about each route.
At the end of the process, when a router
learns about a route to a subnet, all the
router knows is:
◦ Measurement of distance (the metric)
◦ The next-hop router and outgoing interface to use
for that route (a vector, or direction).
Distance Vector Concepts
Distance Vector Concepts
Distance Vector Operation in a Stable
Network
Routing Loops
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The slow convergence of distance vector
routing protocols can result in
◦ inconsistent routing tables
◦ routing loops.
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Routing loops can occur because every
router isn’t updated simultaneously
Route Poisoning
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Distance vector protocols spread the bad
news about a route failure by poisoning the
route.
Route poisoning refers to the practice of
advertising a route, but with a special metric
value called infinity.
Routers consider routes advertised with an
infinite metric to have failed.
Route Poisoning
Route Poisoning
Counting to Infinity Problem
Counting to Infinity Problem
Split Horizon
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In routing updates sent out interface X, do
not include routing information about routes
that refer to interface X as the outgoing
interface.
Split horizon means that when router R1
learns a route from router R2, R1 has no need
to advertise that same route back to router
R2.
Split Horizon
Poison Reverse and Triggered Updates
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Distance vector protocols ensures that every
router learns that the route has failed as
quickly as possible.
◦ Triggered update: When a route fails, do not wait
for the next periodic update. Instead, send an
immediate triggered update listing the poisoned
route.
◦ Poison reverse: When learning of a failed route,
suspend split-horizon rules for that route, and
advertise a poisoned route.
Poison Reverse and Triggered Updates
Counting to Infinity in a Redundant
Network
Counting to Infinity in a Redundant
Network
Holddown Timer
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After hearing a poisoned route, start a
holddown timer for that one route.
Until the timer expires, do not believe any
other routing information about the failed
route, because believing that information may
cause a routing loop.
However, information learned from the
neighbor that originally advertised the working
route can be believed before the holddown
timer expires.
Holddown Timer
RIP
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Routing Information Protocol
Use hop count as metric
Can load balance up to 6 equal cost paths
(default = 4)
Maximum hop count 15
RIPv1 use default subnet mask (classful)
RIPv2 supports VLSM and Discontiguous
networks
RIP Timers
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Route Update Timer
◦ 30 seconds
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Route Invalid Timer
◦ 90 seconds
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Hold-down Timer
◦ 180 seconds
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Route Flush Timer
◦ 240 seconds
◦ Remove the route from the routing table
Configuring RIP Routing
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Router(config)#router rip
Router(config-router)#network network-number*
10.3.5.0
172.16.10.0
router RIP
router RIP
network 172.16.0.0
network 10.0.0.0
network 172.16.0.0
network 192.168.10.0
*Network is a classful network address.
Passive Interface
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Maybe you don’t want to send RIP updates out
your router interface connected to the Internet.
Use the passive-interface command:
Router(config)#router rip
Router(config-router)#passive-interface serial0
Internet
X
S0
Updates
Gateway
This allows a router to receive route updates on an
interface, but not send updates via that interface
RIP version 1
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Example 1
RIP Version 2
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Allows the use of variable length subnet
masks (VLSM) by sending subnet mask
information with each route update
Distance Vector – same AD, and timers.
Easy configuration, just add the command
“version 2” under the router rip configuration
router rip
network 10.0.0.0
version 2
Discontiguous Addressing
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Two networks of the same classful networks
are separated by a different network address
172.16.10.0/24
172.16.11.0/24
10.1.1.0/24
– RIPv1 and IGRP do not advertise subnet masks, and
therefore cannot support discontiguous subnets.
– OSPF, EIGRP, and RIPv2 can advertise subnet masks,
and therefore can support discontiguous subnets.
RIPv1 vs. RIPv2
Verifying RIP
Router#show ip route
Router#show ip protocols
Router#debug ip rip
Router#undebug all
Verifying RIP
Verifying RIP
R1# show ip protocols
Verifying RIP
IGRP
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Interior Gateway Routing Protocol
Cisco proprietary
Use bandwidth and delay as default
composite metric
Can use also another metrics as load,
reliability and MTU
Load balance up to 6 routes (default = 4)
Use bandwidth to determine how to load
balance between routes (not equal cost)
IGRP Timers
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Route Update Timer
◦ 90 seconds
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Route Invalid Timer
◦ 3 * 90 seconds
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Hold-down Timer
◦ 3 * 90 + 10 seconds
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Route Flush Timer
◦ 7 * 90 seconds
◦ Remove the route from the routing table
IGRP vs. RIP
Thank you