Ca Ex S2 M02 Static Routing
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Transcript of Ca Ex S2 M02 Static Routing
CCNA – Semester 2
Chapter 2 - Static Routing
CCNA Exploration 4.0
2
Objectives
• Define the general role a router plays in networks.
• Describe the directly connected networks, different router
interfaces
• Examine directly connected networks in the routing table
and use the CDP protocol
• Describe static routes with exit interfaces
• Describe summary and default route
• Examine how packets get forwarded when using static
routes
• Identify how to manage and troubleshoot static routes
3
Routers and Network
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Role of the Router
• The router is a special-purpose computer that plays a key
role in the operation of any data network. Routers are
primarily responsible for interconnecting networks by:
– Determining the best path to send packets
– Forwarding packets toward their destination
5
Introducing the topology
• Topology Lab
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Introducing the topology
• Topology Lab
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Reference: Cisco router 1841’s Component
Product Description Quantity
CISCO1841
Modular Router w/2xFE, 2 WAN slots, 32
FL/128 DR 1
CAB-ACE Power Cord Europe 1
S184IPB-12406T Cisco 1841 IOS IP BASE W/O CRYPTO 1
WIC-2T 2-Port Serial WAN Interface Card 1
CAB-SS-V35FC
V.35 Cable, DCE Female to Smart Serial, 10
Feet 2
CAB-SS-V35MT V.35 Cable, DTE Male to Smart Serial, 10 Feet 2
MEM1800-32CF 32MB Cisco 1800 Compact Flash 1
ROUTER-SDM-CD CD for SDM software 1
CON-OSP-
CISCO1841 ONSITE 24X7X4 Modular Router w/2xF 1
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Cable Standards
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Cable for LAN/WAN interfaces
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Examining the Connections of the Router
• Serial Connectors
– DB-60 port and Smart port: five-in-one serial port:
• EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA/TIA-530 standards
• Ethernet Connectors
– 2 types of connectors can be used: Straight through and Cross-over
Straight through used to connect:
• Switch-to-Router, Switch-to-PC, Router-to-Server, Hub-to-PC, Hub-to-Server
Cross-over used to connect:
• Switch-to-Switch, PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-Router
11
Router Configuration Review
12
Examining Router Interfaces
• Examining Router Interfaces
– show ip route command – used to view routing table
– show interfaces command – used to show status of an interface
– show ip interface brief command – used to show a portion of the
interface information
– show running-config command – used to show configuration file
in RAM
13
Configuring an Ethernet Interface
• Configuring an Ethernet interface
– By default all serial and Ethernet interfaces are down
– To enable an interface use the no shutdown command
14
Configuring an Ethernet Interface
• Verifying Ethernet interface
– Show interfaces for fastEthernet 0/0 – command
used to show status of fast Ethernet port
– Show ip interface brief
– Show running-config
• Ethernet interfaces participate in ARP
15
Logging Synchronous Command
• In order to keep the unsolicited output separate from your input,
enter line configuration mode for the consoled port and add the
logging synchronous command.
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Configuring a Serial Interfaces
• Configuring a Serial interface
– Enter interface configuration mode
– Enter in the ip address and subnet mask
– Enter in the no shut down command
• Example:
– R1(config)#interface serial 0/0
– R1(config-if)#ip address 172.16.2.1 255.255.255.0
– R1(config-if)#no shutdown
17
Examining Router Interfaces
• Examining Router Interfaces
– Physically connecting a WAN Interface.
– A WAN Physical Layer connection has sides:
Data Circuit-terminating Equipment (DCE) – This
is the service provider. CSU/DSU is a DCE
device.
Data Terminal Equipment (DTE) – Typically the
router is the DTE device.
18
Examining Router Interfaces
• Configuring serial links in a lab environment
One side of a serial connection must be considered
a DCE
This requires placing a clocking signal – use the
clock rate command.
Example:
• R1(config)#interface serial 0/0
• R1(config-if)#clockrate 64000
Serial Interfaces require a clock signal to control the
timing of the communications.
• Note: Wic-2a/s support maximum clock rate is 128000 bps
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Examining Router Interfaces
• Verifying the Serial Interface Configuration
– show interfaces command
– show ip interface brief command
– show running-config
– ping command
– show ip route
20
Verifying Changes to the Routing Table
• The routing table consists of a list of "known" network addresses
- that is, those addresses that are directly connected, configured
statically, and learned dynamically.
21
Verifying Changes to the Routing Table
• Observing Routes as They are Added to the Routing Table
– debug ip routing command will let us see any changes that
the router performs when adding or removing routes.
22
Devices on Directly Connected Networks
• When a router only has its interfaces configured, and the routing
table contains the directly connected networks but no other
routes, only devices on those directly connected networks are
reachable.
23
Devices on Directly Connected Networks
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Cisco Discovery Protocol (CDP)
Network discovery with CDP
• CDP is an information-gathering tool used by network administrators to
get information about directly connected Cisco devices.
• CDP is a proprietary tool that enables you to access a summary of
protocol and address information about Cisco devices that are directly
connected.
• These advertisements contain information such as the types of devices
that are connected, the router interfaces they
are connected to, the interfaces used to
make the connections, and the model
numbers of the devices.
• Concept of neighbors
– 2 types of neighbors
Layer 3 neighbors
Layer 2 neighbors
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Cisco Discovery Protocol (CDP)
CDP Operation
• CDP runs at the Data Link layer connecting the physical media to the
upper-layer protocols (ULPs).
• Cisco network devices, such as routers that support different Network
layer protocols (for example, IP and Novell IPX), can learn about each
other
• CDP provides the following information about each CDP neighbor
device:
– Device identifiers
– Address list
– Port identifier
– Capabilities list
– Platform
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Default Setting
Feature Default Setting
CDP global state Enabled
CDP interface state Enabled
CDP holdtime (packet holdtime in seconds) 180
CDP timer (packets sent every x seconds) 60
27
Using CDP for Network Discovery
• The information gathered by the CDP protocol can be
examined with the show cdp neighbors command.
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Using CDP for Network Discovery
Field Definition
Device ID The name of the neighbor device and either the
MAC address or the serial number of this
device.
Local Intrfce The protocol being used by the connectivity
media.
Holdtme The remaining amount of time (in seconds) the
current device will hold the CDP advertisement
from a sending router before discarding it.
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Using CDP for Network Discovery
Capability
(Capability
Codes)
Capability (type of routing device) of the listed
neighboring device.
The capability types that can be discovered are:
R—Router
T—Transparent bridge
B—Source-routing bridge
S—Switch
H—Host
I— device is using IGMP
r—Repeater
Platform The product number of the device.
Port ID The protocol and port number of the device.
30
Using CDP for Network Discovery
31
CDP Commands
32
CDP Commands
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CDP Commands
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CDP Commands
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Static Routes
with “Next Hop” Addresses
36
Purpose and Command Syntax of ip route
• Static routes are commonly used when routing from a network to
a stub network.
– A stub network is a network accessed by a single route.
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Purpose and Command Syntax of ip route
38
Configuring Static Routes
• Installing a Static Route in the Routing Table
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Verifying Static Route Commands
Configuring Routes to Two More Remote Networks
40
Routing Table Principles and Static Routes
41
Routing Table Principles and Static Routes
• Applying the Principles
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Resolving to an Exit Interface
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Resolving to an Exit Interface
• Exit Interface is down
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Static Routes with Exit Interface
45
Configuring a Static Route with an Exit Interface
• Static routes can be configured with an exit interface, which
allows the routing table to resolve the exit interface in a single
search instead of two searches.
46
Configuring a Static Route with an Exit Interface
• Static Route and an Exit Interface
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Modifying Static Routes
• There are times when a previously configured static route needs to be
modified:
– The destination network no longer exists, and therefore the static
route should be deleted.
– There is a change in the topology, and either the intermediate
address or the exit interface has to be changed.
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Verifying the Static Route Configuration
• Use the following commands
Step 1: show running-config
Step 2 verify static route has been entered correctly
Step 3: show ip route
Step 4 verify route was configured in routing table
Step 5 issue ping command to verify packets can reach destination
and that Return path is working
49
Static Routes with Ethernet Interfaces
• Ethernet interfaces and ARP.
– If a static route is configured on an Ethernet link, if the packet is
sent to the next-hop router then
• the destination MAC address will be the address of the next
hop’s Ethernet interface
• This is found by the router consulting the ARP table
– If an entry isn’t found then an ARP request will be sent out
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Static Routes with Ethernet Interfaces
Static routes and Ethernet exit interfaces
• With Ethernet networks, may be many different devices sharing
the same multi-access network so the router does not know the
next-hop IP address and it cannot determine the destination
MAC address for the Ethernet frame.
51
Summary and Default Static Routes
52
Summary Static Routes
• Summarizing Routes to Reduce the Size of the Routing Table
• Route Summarization: Multiple static routes can be summarized into a
single static route if:
– The destination networks can be summarized into a single network
address, and
– The multiple static routes all use the same exit-interface or next-
hop IP address
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Summary Static Routes
• Configuring a Summary Route:
Step 1: Delete the current
static route
Step 2: Configure the
summary static route
Step 3: Verify the new static
route
54
Default Static Route
• A default static route is a route that will match all packets. Default static
routes are used:
– When no other routes in the routing table match the packet's
destination IP address. In other words, when a more specific match
does not exist. A common use is when connecting a company's
edge router to the ISP network.
– When a router has only one other router to which it is connected.
This condition is known as a stub router.
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Default Static Route
• Verifying a Default Static Route
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Managing and
Troubleshooting Static Route
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Static Routes and Packet Forwarding
• Static Routes and Packet Forwarding
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Static Routes and Packet Forwarding
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Static Routes and Packet Forwarding
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Static Routes and Packet Forwarding
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Static Routes and Packet Forwarding
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Static Routes and Packet Forwarding
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Static Routes and Packet Forwarding
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Troubleshooting a Missing Route
• Tools that can be used to isolate routing problems include:
– ping– tests end to end connectivity
– traceroute– used to discover all of the hops (routers) along
the path between 2 points
– show IP route – used to display routing table & ascertain
forwarding process
– show ip interface brief - used to show status of router
interfaces
– show cdp neighbors detail – used to gather configuration
information about directly connected neighbors
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Solving the Missing Route
• Finding a missing or miss-configured route requires methodically using
the correct tools
– Start with ping. If ping fails then use traceroute to determine
where packets are failing to arrive
• Issue: show ip route to examine routing table.
– If there is a problem with a miss-configured static route remove the
static route then reconfigure the new static route
Solving:
– R2(config)#no ip route 172.16.3.0 255.255.255.0 serial0/0/1
– R2(config)#ip route 172.16.3.0 255.255.255.0 serial 0/0/0
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Basic Static Route Configuration Lab
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Challenge Static Route Configuration Lab
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Summary
69