Chapter 15: Operating Cisco Routers

description text

An interface subcommand with which you can type a string of text to document information about that particular interface.

1. Which of the following installation steps are more likely required on a Cisco router, but not typically required on a Cisco switch? (Choose two answers.) a. Connect Ethernet cables b. Connect serial cables c. Connect to the console port d. Connect the power cable e. Turn the on/off switch to "on"

B and E. Cisco routers have an on/off switch, but Cisco switches generally do not

interface type number

Global command that moves the user into configuration mode of the named interface.

speed {10 | 100 | 1000}

Interface command for router Gigabit (10/100/1000) interfaces that sets the speed at which the router interface sends and receives data.

duplex {full | half | auto}

Interface command that sets the duplex, or sets the use of IEEE autonegotiation, for router LAN interfaces that support multiple speeds.

[no] shutdown

Interface subcommand that enables (no shutdown) or disables (shutdown) the interface.

ip address address mask

Interface subcommand that sets the router's IPv4 address and mask.

show interfaces [type number]

Lists a large set of informational messages about each interface, or about the one specifically listed interface.

show ip interface brief

Lists a single line of information about each interface, including the IP address, line and protocol status, and the method with which the address was configured (manual or Dynamic Host Configuration Protocol [DHCP]).

show protocols [type number]

Lists information about the listed interface (or all interfaces if the interface is omitted), including the IP address, mask, and line/protocol status.

3. Which answers list a task that could be helpful in making a router interface G0/0 ready to route packets? (Choose two answers.) a. Configuring the ip address address mask command in G0/0 configuration mode b. Configuring the ip address address and ip mask mask commands in G0/0 configuration mode c. Configuring the no shutdown command in G0/0 configuration mode d. Setting the interface description in G0/0 configuration mode

A and C. To route packets on an interface, the router interface configuration must include an IP address and mask. One correct command shows the correct single com- mand used to configure both values, while one incorrect command shows those set- tings as two separate commands. Also, to route packets, the interface must reach an "up/up" state; that is, the show interfaces and other commands list two status values, and both must be "up." The no shutdown command enables the interface.

Enterprise router

A term to describe the general role of a router as a router at a permanent site owned or leased by the enterprise, like an office building, manufacturing facility, branch office, or retail location. These sites typically have enough users to justify separate routers, switches, and wireless access points, and are more likely to justify private WAN services, in comparison to SOHO routers.

SOHO router

A term to describe the general role of a router that exists as part of the enter- prise network but resides at an employee's home or at a smaller business site, possibly with a short-term lease compared to larger enterprise sites. These sites typically have few devices, so it makes sense to use one device that integrates routing, switches, wireless, and other features into a single device (the SOHO router) and are more likely to justify Internet access as the pri- mary WAN access method.

6. Which of the following is different on the Cisco switch CLI for a Layer 2 switch as compared with the Cisco router CLI? a. The commands used to configure simple password checking for the console b. The number of IP addresses configured c. The configuration of the device's hostname d. The configuration of an interface description

B. A router has one IPv4 address for each interface in use, whereas a LAN switch hasa single IPv4 address that is just used for accessing the switch. The rest of the answers list configuration settings that use the same conventions on both routers and switches.

2. Which of the following commands might you see associated with a router CLI, but not with a switch CLI? a. The show mac address-table command b. The show ip route command c. The show running-config command d. The show interfaces status command

B. Cisco routers that do not also have any Layer 2 switch features support commands needed for Layer 3 routing as well as commands in common between Layer 2 switch- ing and Layer 3 routing devices. In this case, the show interfaces status and show mac address-table commands happen to be commands supported on Layer 2 switches but not on routers. Both types of devices use the show running-config command. Of the answers, only the show ip interface brief command is unique to routers.

5. Which of the following commands do not list the IP address and mask of at least one interface? (Choose two answers.) a. show running-config b. show protocols type number c. show ip interface brief d. show interfaces e. show version

C and E. The show ip interface brief command lists all the interface IPv4 addresses but none of the masks. The show version command lists none of the IP addresses and none of the masks. The other three commands list both the address and mask.

4. The output of the show ip interface brief command on R1 lists interface status codes of "down" and "down" for interface GigabitEthernet 0/0. The interface connects to a LAN switch with a UTP straight-through cable. Which of the following could be true? a. The shutdown command is currently configured for router interface G0/0. b. The shutdown command is currently configured for the switch interface on the other end of the cable. c. The router was never configured with an ip address command on the interface. d. The router was configured with the no ip address command.

C. If the first of the two status codes is "down," it typically means that a Layer 1 prob- lem exists. In this case, the question states that the router connects to a switch with a UTP straight-through cable, which is the correct cable pinout. Of the two answers that mention the shutdown command, if the router interface were shut down, the first rout- er status code would be "administratively down," so that answer is incorrect. However, if the neighboring device interface sits in a shutdown state, the router will sense no electrical signals over the cable, seeing that as a physical problem, and place the inter- face into a "down/down" state, making that answer correct. Second, the two answers that mention interface IP addresses have no impact on the status codes of the show interfaces brief command. Both answers imply that the interface does not have an IP address configured. However, both the first and second status codes are not related to whether IP addresses have been configured or not, making both answers incorrect.

Integrated Services Router (ISR)

Cisco's long-running term for several different model series of Enterprise-class routers, intended mostly for use as enterprise routers and some use as SOHO routers. ISR routers first serve as routers but, depending on the family or specific model, support all current types of WAN connections (private and Internet), LAN switching ports, Wireless APs, VPNs, and other integrated functions supported in a single device.