List the information required by a router to successfully route packets.
Describe the basic IP
routing process.
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You need to remember
that the frame changes at each hop but that the packet is never changed or
manipulated in any way until it reaches the destination device (the TTL field
in the IP header is decremented for each hop, but that's it!).
List the information
required by a router to successfully route packets.
·
To be able to route
packets, a router must know, at a minimum, the destination address, the
location of neighboring routers through which it can reach remote networks,
possible routes to all remote networks, the best route to each remote network,
and how to maintain and verify routing information.
Describe how MAC
addresses are used during the routing process.
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A MAC (hardware)
address will only be used on a local LAN. It will never pass a router's
interface. A frame uses MAC (hardware) addresses to send a packet on a LAN. The
frame will take the packet to either a host on the LAN or a router's interface
(if the packet is destined for a remote network). As packets move from one
router to another, the MAC addresses used will change, but normally the
original source and destination IP addresses within the packet will not.
View and interpret the
routing table of a router.
·
Use the show ip route
command to view the routing table. Each route will be listed along with the
source of the routing information. A C to the left of the route will indicate
directly connected routes, and other letters next to the route can also
indicate a particular routing protocol that provided the information, such as,
for example, R for RIP.
Differentiate the
three types of routing.
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The three types of
routing are static (in which routes are manually configured at the CLI),
dynamic (in which the routers share routing information via a routing
protocol), and default routing (in which a special route is configured for all
traffic without a more specific destination network found in the table).
Compare and contrast
static and dynamic routing.
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Static routing creates
no routing update traffic and creates less overhead on the router and network
links, but it must be configured manually and does not have the ability to
react to link outages. Dynamic routing creates routing update traffic and uses
more overhead on the router and network links.
Configure static
routes at the CLI.
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The command syntax to
add a route is ip route [destination_network] [mask] [next-hop_address or
exitinterface] [administrative_distance] [permanent]
Create a default
route.
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To add a default
route, use the command syntax ip route 0.0.0.0 0.0.0.0 ip-address or exit
interface type and number.
Understand
administrative distance and its role in the selection of the best route.
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Administrative
distance (AD) is used to rate the trustworthiness of routing information
received on a router from a neighbor router. Administrative distance is an
integer from 0 to 255, where 0 is the most trusted and 255 means no traffic
will be passed via this route. All routing protocols are assigned a default AD,
but it can be changed at the CLI.
Differentiate
distance-vector, link-state and hybrid routing protocols.
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Distance-vector
routing protocols make routing decisions based on hop count (think RIP), while
link-state routing protocols are able to consider multiple factors such as
bandwidth available and building a topology table. Hybrid routing protocols
exhibit characteristics of both types.
Configure RIP routing.
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To configure RIP
routing, first you must be in global configuration mode and then you type the
command router rip . Then you add all directly connected networks, making sure
to use the classful address and the version 2 command and to disable
auto-summarization.
At the appropriate command
prompt, create a static route to network 172.16.10.0/24 with a next-hop gateway
of 172.16.20.1 and an administrative distance of 150.
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router(config) #ip
route 172.16.10.0 255.255.255.0 172.16.20.1 150
When a PC sends a
packet to another PC in a remote network, what destination addresses will be in
the frame that it sends to its default gateway?
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It will use the
gateway interface MAC at L2 and the actual destination IP at L3.
At the appropriate
command prompt, create a default route to 172.16.40.1.
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router(config) #ip
route 0.0.0.0 0.0.0.0 172.16.40.1
On which type of
network is a default route most beneficial?
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Stub network
At the appropriate
command prompt, display the routing table on your router.
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Router# show ip route
When creating a static
or default route, you don't have to use the next-hop IP address; you can use
the ___________________.
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Exit interface
True/False: To reach a
remote host, you must know the MAC address of the remote host.
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False. The MAC address
would be the router interface, not the remote host.
True/False: To reach a remote host, you must know the IP address
of the remote host.
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True
At the appropriate
command prompt(s), prevent a router from propagating RIP information out serial
1. 10. True/False: RIPv2 is considered classless.
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router(config)# router
rip
router(config-router)# passive-interface S1
True/False: RIPv2 is
considered classless.
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True
What command was used
to generate the following output? Codes: L - local, C - connected, S - static,
[output cut] 10.0.0.0/8 is variably subnetted, 6 subnets, 4 masks C 10.0.0.0/8
is directly connected, FastEthernet0/3 L 10.0.0.1/32 is directly connected, FastEthernet0/3
C 10.10.0.0/16 is directly connected, FastEthernet0/2 L 10.10.0.1/32 is
directly connected, FastEthernet0/2 C 10.10.10.0/24 is directly connected,
FastEthernet0/1 L 10.10.10.1/32 is directly connected, FastEthernet0/1 S*
0.0.0.0/0 is directly connected, FastEthernet0/0
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show ip route The ip
route command is used to display the routing table of a router.
You are viewing the
routing table and you see an entry 10.1.1.1/32. What legend code would you
expect to see next to this route?
A. C
B. L
C. S
D. D
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B. In the new 15 IOS
code, Cisco defines a different route called a local route. Each has a /32
prefix defining a route just for the one address.
Which of the following
statements are true regarding the command ip route 172.16.4.0 255.255.255.0
192.168.4.2 ? (Choose two.)
A. The command is used to establish a static route.
B. The default administrative distance is used.
C. The command is used to configure the default route.
D. The subnet mask for the source address is 255.255.255.0.
E. The command is used to establish a stub network.
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A, B. Although option
D almost seems right, it is not; the mask is the mask used on the remote
network, not the source network. Since there is no number at the end of the
static route, it is using the default administrative distance of 1.
Using the output
shown, what protocol was used to learn the MAC address for 172.16.10.1?
Interface: 172.16.10.2 --- 0x3 Internet Address Physical Address Type
172.16.10.1 00-15-05-06-31-b0 dynamic
A. ICMP
B. ARP
C. TCP
D. UDP
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B. This mapping was
learned dynamically which means it was learned through ARP.
Using the output
shown, what protocol was used to learn the MAC address for 172.16.10.1?
Interface: 172.16.10.2 --- 0x3 Internet Address Physical Address Type
172.16.10.1 00-15-05-06-31-b0 dynamic
A. ICMP
B. ARP
C. TCP
D. UDP.
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B. This mapping was
learned dynamically which means it was learned through ARP.
When a packet is
routed across a network, the ______________ in the packet changes at every hop
while the ____ does not.
A. MAC address, IP address
B. IP address, MAC address
C. Port number, IP address
D. IP address, port number
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Since the destination
MAC address is different at each hop, it must keep changing. The IP address
which is used for the routing process does not.
Which statement is
true regarding classless routing protocols? (Choose two.)
A. The use of discontiguous networks is not allowed.
B. The use of variable length subnet masks is permitted.
C. RIPv1 is a classless routing protocol.
D. IGRP supports classless routing within the same autonomous system.
E. RIPv2 supports classless routing.
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B, E. Classful routing
means that all hosts in the internetwork use the same mask and that only
default masks are in use. Classless routing means that you can use variable
length subnet masks (VLSMs).
distance-vector and
link-state routing protocols? (Choose two.)
A. Link state sends its complete routing table out of all active interfaces at
periodic time intervals.
B. Distance vector sends its complete routing table out of all active
interfaces at periodic time intervals.
C. Link state sends updates containing the state of its own links to all
routers in the internetwork.
D. Distance vector sends updates containing the state of its own links to all
routers in the internetwork.
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B, C. The
distance-vector routing protocol sends its complete routing table out of all
active interfaces at periodic time intervals. Link-state routing protocols send
updates containing the state of their own links to all routers in the internetwork.
When a router looks up
the destination in the routing table for every single packet it is called
_____________ .
A. dynamic switching
B. fast switching
C. process switching
D. Cisco Express Forwarding
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C. This is how most
people see routers, and certainly they could do this type of plain ol' packet
switching in 1990 when Cisco released their very first router and traffic was
seriously slow, but not in today's networks! This process involves looking up
every destination in the routing table and finding the exit interface for every
packet.
What type(s) of route
is the following? Choose all that apply. S* 0.0.0.0/0 [1/0] via 172.16.10.5
A. Default
B. Subnetted
C. Static
D. Local
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A, C. The S* shows
that this is a candidate for default route and that it was configured manually.
A network
administrator views the output from the show ip route command. A network that
is advertised by both RIP and EIGRP appears in the routing table flagged as an
EIGRP route. Why is the RIP route to this network not used in the routing
table?
A. EIGRP has a faster update timer.
B. EIGRP has a lower administrative distance.
C. RIP has a higher metric value for that route.
D. The EIGRP route has fewer hops.
E. The RIP path has a routing loop.
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B. RIP has an
administrative distance (AD) of 120, while EIGRP has an administrative distance
of 90, so the router will discard any route with a higher AD than 90 to that
same network.
Which of the following
is NOT an advantage of static routing?
A. Less overhead on the router CPU
B. No bandwidth usage between routers
C. Adds security
D. Recovers automatically from lost routes
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D. Recovery from a
lost route requires manual intervention by a human to replace the lost route.
What metric does RIPv2
use to find the best path to a remote network?
A. Hop count
B. MTU
C. Cumulative interface delay
D. Load
E. Path bandwidth value
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RIPv1 and RIPv2 only
use the lowest hop count to determine the best path to a remote network.
The Corporate router
receives an IP packet with a source IP address of 192.168.214.20 and a
destination address of 192.168.22.3. Looking at the output from the Corp
router, what will the router do with this packet? Corp# sh ip route [output
cut] R 192.168.215.0 [120/2] via 192.168.20.2, 00:00:23, Serial0/0 R
192.168.115.0 [120/1] via 192.168.20.2, 00:00:23, Serial0/0 R 192.168.30.0
[120/1] via 192.168.20.2, 00:00:23, Serial0/0 C 192.168.20.0 is directly
connected, Serial0/0 C 192.168.214.0 is directly connected, FastEthernet0/0
A. The packet will be discarded.
B. The packet will be routed out of the S0/0 interface.
C. The router will broadcast looking for the destination.
D. The packet will be routed out of the Fa0/0 interface.
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Since the routing
table shows no route to the 192.168.22.0 network, the router will discard the
packet and send an ICMP destination unreachable message out of interface
FastEthernet 0/0, which is the source LAN from which the packet originated.
If your routing table
has a static, an RIP, and an EIGRP route to the same network, which route will
be used to route packets by default?
A. Any available route
B. RIP route
C. Static route
D. EIGRP route
E. They will all load-balance.
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C. Static routes have
an administrative distance of 1 by default. Unless you change this, a static
route will always be used over any other dynamically learned route. EIGRP has
an administrative distance of 90, and RIP has an administrative distance of
120, by default.
Which of the following
is an EGP?
A. RIPv2
B. EIGRP
C. BGP
D. RIP
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C. BGP is the only EGP
listed.
Which of the following
is an advantage of static routing?
A. Less overhead on the router CPU
B. No bandwidth usage between routers
C. Adds security
D. Recovers automatically from lost routes
·
D. Recovery from a
lost route requires manual intervention by a human to replace the lost route.
The advantages are less overhead on the router and network, as well as more
security.
What command produced
the following output? Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.10.1 YES manual up up FastEthernet0/1 unassigned YES
unset administratively down down Serial0/0/0 172.16.10.2 YES manual up up
Serial0/0/1 unassigned YES unset administratively down down
A. show ip route
B. show interfaces
C. show ip interface brief
D. show ip arp
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C. The show ip
interface brief command displays a concise summary of the interfaces.
In the following
command what does the 150 at the end of the command mean? Router(config)# ip
route 172.16.3.0 255.255.255.0 192.168.2.4 150
A. Metric
B. Administrative distance
C. Hop count
D. Cost
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B. The 150 at the end
changes the default administrative distance (AD) of 1 to 150.
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