Ch18-Configuring IPv4 Addresses and Static Routes

Question 1

On an IP host, the IP address of some router to which the host sends packets when the packet’s destination address is on a sunset other than the local subnet

Answer 1

default gateway/router

Question 2

A list of IP addresses of neighbors on the same VLAN, along with their MAC addresses, as kept in memory by hosts and routers

Answer 2

ARP table

Question 3

A list of routes in a router, with each route listing the destination subnet and mask, the routers interface out which to forward packets destined for the subnet, and as needed, the next-hop routers IP address

Answer 3

routing table

Question 4

In an IP routing table, part of a routing table entry that refers to the local interface out which the local router should forward packets that match the route.

Answer 4

Outgoing interface

Exit Interface

Egress interface

Question 5

One of the virtual interfaces on a single physical interface

Answer 5

sub-interface

Question 6

A configuration concept inside Cisco switches, used as an interface between IOS running on the switch and a VLAN supported inside the switch, so that the switch can assign an IP address and send packets into that VLAN

Answer 6

VLAN interface

Question 7

A LAN switch that can also perform Layer3 routing functions.

Answer 7

Layer 3 switch

Question 8

On a router, an IP route added to the routing table when the router interface is both up and has an IP address configured. The route is for the subnet that can be calculated given the configured IP address and mask

Answer 8

connected route

Question 9

On a router, the route that is considered to match all packets that are not otherwise matches by some more specific route

Answer 9

default route

Question 10

An IP route on a router created by the user configuring the details of that route on the local router

Answer 10

static route

Question 11

A route with a /32 mask, which by virtue of this mask represents a route to a single host IP address

Answer 11

host route

Question 12

A static IP route that uses a higher administrative distance than other routes, typically routes learned by a routing protocol. As a result, the router will not use the static route if the routing protocol route has been learned, but will use the static route if the routing protocol fails to learn the route

Answer 12

floating static route

Question 13

A route for a classful network

Answer 13

network route

Question 14

In Cisco routers, a means for one router to choose between multiple routes to reach the same subnet when those routes are learned by different routing protocols. A measure of the “trustworthiness” of learned routes. The lower its value, the better the source of the routing information

Answer 14

administrative distance

Question 15

Command reference:

Global command to create a sub interface and to enter configuration mode for that sub interface

Answer 15

interface int-type-num.subint

Question 16

Command reference:

A subinterface cmmand that tells the router to use 802.1Q trunking, for a particular VLAN, and with the native keyword, to not encapsulate in a trunking header.

Answer 16

encapsulation dot1q vland-id [native]

Question 17

Command reference:

A command on Cisco switches that enables the switch to support IP routing

Answer 17

sdm prefer lanbase-routing

Question 18

Command reference:

Global command that enables or disables the routing of IPv4 packets on a router or Layer 3 switch

Answer 18

[no] ip routing

Question 19

Command reference:

Global command on a Layer 3 switch to create a VLAN interface and to enter configuration mode for that VLAN interface

Answer 19

interface vlan vlan-id

Question 20

Command reference:

Global configuration command that creates a static route

Answer 20

ip route address mask egress-int [distance] [permanent]

Question 21

Command reference:

List the router’s entire routing table

Answer 21

show ip route

Question 22

Command reference:

A subinterface cmmand that tells the router to use 802.1Q trunkin, for a particular VLAN, and with the native keyword, to not encapsulate in a trunking header.

Question 23

Command reference:

Lists a subset of the routing table

Answer 23

show ip route [connected | static | rip]

Question 24

Command reference:

Lists detailed information about the route that a router matches for the given IP address

Answer 24

show ip route ip-addr

Question 25

Command reference:

Lists VLAN configuration and statistics for VLAN trunks configured on routers

Answer 25

show vlans

Question 26

Command reference:

Lists the routers IPv4 ARP cache

Answer 26

show ip arp

show arp

Question 27

Command reference:

Removes all dynamically learned ARP table entries, or if the command lists an IP address, removes the entry for that address only

Answer 27

clear ip arp [ip-addr]

Question 28

Which command produced the following output?

Answer 28

show ip route

Question 29

Which commands would have produced the following output?

Answer 29

show arp / show ip arp

Question 30

Consider a host attempting to send a packet to a destination on its local subnet. The host will perform two actions prior to sending that packet. What will those two actions be?

Answer 30

1. Determine host destination MAC address (check its ARP table and ARP if necessary)
2. Encapsulate packet in a frame with the destination MAC address of the destination host.

Question 31

Consider a host attempting to send a packet to a destination that is not on its local subnet. The host will perform two actions prior to sending that packet. What will those two actions be?

Answer 31

1. Determine the default gateway destination MAC address (ARP table, ARP if necessary).
2. Encapsulate the packet in a frame with the default gateway’s MAC address as the destination MAC address.

Question 32

A router has just received a frame with a packet destined for a device on another subnet. The router must now decide to foward or filter that frame. As part of the decision proces, what two actions will the router take?

Answer 32

1. Examine the frame for errors (inspect FCS).
2. Ensure the destination MAC address is, in fact, the router’s MAC address (or a multicast or broadcast address).

If the frame has no errors, and the destination MAC address belongs to the router, the frame will be processed. Otherwise, it will be filtered.

Question 33

A router has received a frame with a packet destined for another subnet. The router has processed the frame and de-encapsulated the packet. What is the router’s next step?

Answer 33

Examine the destination IP address of the packet, and attempt to find a suitable match for that destination in the routing table.

Question 34

A router has matched the destination IP address of an incoming packet with a suitable entry in its routing table. What information is supplied by that routing table entry?

Answer 34

The exit interface (and possibly the next-hop router) that will be used to transmit the packet toward its destination.

Question 35

A router is prepared to send a packet out a specific exit interface. What steps will the router take to accomplish this?

Answer 35

1. If the exit interface is a LAN interface, the router must look to its ARP table (or ARP) to determine the destination’s MAC address.
2. Encapsulate the packet in a frame appropriate for the exit interface

Question 36

A router interface was configured with the intention of creating a connected route. What conditons must be satisfied in order for the router to add this route to its routing table?

Answer 36

The interface must be in an “up/up” state, and the interface must have an assigned IP address.

Question 37

Multiple VLANs are in use within an organization. What options exist for routing between those VLANs?

Answer 37

1. A router with a physical interface for each and every VLAN.
2. A router with VLAN trunking enabled, connected to a trunking port on a switch (ROAS)
3. Use of a Layer 3 switch

Question 38

Consider a design which uses a router-on-a-stick topolgy using multiple subinterfaces. What configuration possibilities are available on the router to account for the native VLAN?

Answer 38

1. Configure an additional subinterface with an IP address and an encapsulation command noting that VLAN as native:

int g0/0.99 encapsulation dot1q 99 native IP address 10.1.99.1 255.255.255.0

2. Configure the physical interface with an IP address, but without an encapsulation command. The router will assume the physical address is using the native VLAN.

Question 39

An expected route does not appear in the routing table. What possible conditions would cause this?

Answer 39

1. Is the outgoing interface up/up?
2. Is the next-hop router not reachable
3. Does a better route with lower administrative distance exist?

Question 40

An incorrect static route appears in the routing table. What conditions could cause this?

Answer 40

1. Is there a subnetting math error in the configuration of the route?
2. Is the next-hop IP correct, and does it reference an IP address on the neighbor router?
3. Is the outgoing interface correct?