ccna explorationg 4.0 - chapter 2 static routing

• 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

Chapter 2-Static Routing

CCNA Exploration 4.0

• 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

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.

Introducing the topology

• Topology Lab

– Three 1800 series routers connected via WAN links.

– Each router connected to a LAN represented by a switch and

a PC.

Cable for LAN/WAN interfaces

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

Configuring an Ethernet Interface

• Configuring an Ethernet interface

– By default all serial and Ethernet interfaces are admintrative down

– To enable an interface use the no shutdown command

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

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.

Configuring a Serial Interfaces

• Configuring a Serial interface

– Enter interface configuration mode

– Enter in the ip address and subnet mask

– Enter in the clock rate(DCE) and no shut down command

Verifying Changes to the Routing Table

• The routing table consists of a list of "known" network addresses these addresses that are directly connected , configured

statically , and learned dynamically

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.

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

Devices on Directly Connected Networks

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

Cisco Discovery Protocol (CDP)

• CDP provides the following information about each CDP neighbor

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

Using CDP for Network Discovery

• The information gathered by the CDP protocol can be examined with the show cdp neighbors command

Using CDP for Network Discovery

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

Using CDP for Network Discovery

H—Host I— device is using IGMP r—Repeater

Platform The product number of the device

Using CDP for Network Discovery

To disable CDP on a specific interface after it has been enabled, use the no CDP enable

command in interface

CDP Commands

CDP Commands

CDP Commands

CDP Commands

STATIC ROUTING

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

ip route command

RTR(config)# ip route prefix mask {address |

interface} [distance] [tag tag] [permanent]

• prefix IP route prefix for the destination

• mask Prefix mask for the destination

• address IP address of the ―next hop‖ that can be used to reach

that network

• interface Network interface to use (exit-interface)

• distance (Optional) An administrative distance

• tag tag (Optional) Tag value that can be used as a "match" value for controlling redistribution via route maps (CCNP Advanced Routing)

• Permanent (Optional) Specifies that the route will not be removed,

even if the interface shuts down (CCNP Advanced Routing)

Configuring Static Routes

• Installing a Static Route in the Routing Table

Configuring Static Routes

Configuring Routes to Two More Remote Networks

Routing Table Principles and Static Routes

Routing Table Principles and Static Routes

• Applying the Principles

Resolving to an Exit Interface

Resolving to an Exit Interface

• Exit Interface is Down

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

ip route command

RTR(config)# ip route prefix mask {address |

interface} [distance] [tag tag] [permanent]

• prefix IP route prefix for the destination

• mask Prefix mask for the destination

• address IP address of the ―next hop‖ that can be used to reach

that network

• interface Network interface to use (exit-interface)

• distance (Optional) An administrative distance

• tag tag (Optional) Tag value that can be used as a "match" value for controlling redistribution via route maps (CCNP Advanced Routing)

• Permanent (Optional) Specifies that the route will not be removed,

even if the interface shuts down (CCNP Advanced Routing)

Configuring a Static Route with an Exit Interface

• Static Route and an Exit Interface

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

Verifying the Static Route Configuration

• 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

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

Static Routes with Ethernet Interfaces

Static routes and Ethernet exit interfaces

• With Ethernet networks, there may be many different devices sharing the same multi-access network, including hosts and even multiple

routers Thefore, router does not know the next-hop IP address and

therefore it cannot determine the destination MAC address for the

Ethernet frame

Summary Static Routes

Route Summarization

• Summarizing Routes to Reduce the Size of the Routing Table

• 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

Summary Static Routes

• Configuring a Summary Route

Configuring a summary route

Step 1: Delete the current static routeStep 2: Configure the summary static routeStep 3: Verify the new static route

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

– Using command: ip route 0.0.0.0 0.0.0.0 {exit Interface, IP

NextHop}

Default Static Route

• Verifying a Default Static Route

Static Routes and Packet Forwarding

• Static Routes and Packet Forwarding

Static Routes and Packet Forwarding

Static Routes and Packet Forwarding

Static Routes and Packet Forwarding

Static Routes and Packet Forwarding

Static Routes and Packet Forwarding

Static Routes and Packet Forwarding

Troubleshooting a Missing Route

• 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

• Serial cables are connected to router serial ports

• In the lab environment clock rates must be configured for DCE

• Straight through cables or cross over cables are used to connect to fastethernet port (The type of cable used depends on what devices are being connected)

• Cisco Discovery Protocol

– A layer 2 proprietary protocol

• Static Routes

– This is a manually configured path that specifies how the

router will get to a certain point using a certain path

• Summary static routes

– This is several static routes that have been condensed into a

single static route

• Default route

– It is the route packets use if there is no other possible match

for their destination in the routing table

• Forwarding of packets when static route are used

– Zinin’s 3 routing principles describe how packets are