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How do you configure the inside interface of a router to use NAT?
While configuring the interface, use the command i p nat inside.
How do you configure the outside interface of a router to use NAT?
While configuring the interface, use the command i p nat outside.
How do you tell a router which traffic to run through NAT?
Create an access list that identifies the traffic that you want to use NAT to control.
Give an example of setting up a NAT access list on a router.
From config mode, use the command i p access-list extended NAT, to call the access list NAT.
How do you define the I P address range for a NAT access list to use?
Use the command "50 permit i p 192.168.0.0 0.0.0.255 any" to start the access list sequence at 50 in case you want to put any exclusions in the access list later. This example would cause all traffic from the 192.0.0.0 network to flow through NAT.
After creating a NAT access list, what is the final step to enable it on the router?
You have to turn on the NAT inside interface with the command "i p nat inside source list NAT int g0/1 overload". That would enable the access list called NAT to become active on int g0/1.
What is the purpose behind the "overload" keyword in the command to turn on NAT on a router?
Overload tells the router to use Port Address Translation, or PAT.
What are the 2 commands that can be used to see the status of NAT on a router?
show i p nat statistics and show i p nat translations.
When using static NAT, do you need to configure an ACL?
No, when using static NAT, everything is configured in the NAT statement.
What is the command to set up static NAT on a router?
i p nat inside source static 192.168.1.2 100.65.0.2. That would set up a permanent NAT from the I P address 192.168.1.2 that would always be translated to the address 100.65.0.2.
What is Dynamic NAT with Pools?
A pool of inside global I P addresses, also known as publicly routable addresses, is dynamically assigned one-to-one to ACL defined hosts in the network. As each inside host uses one of the available NAT I P addresses, it is no longer available for use.
How do you implement Dynamic NAT with Pools?
Set an inside interface to use NAT with the commands int g0/1 followed by i p nat inside. Exit out of interface config and then use the command i p nat pool 1-pool 100.65.3.1. 100.65.3.255 netmask 255.255.255.0. All NAT addresses would be between 100.65.3.1 and 100.65.3.255.
After setting up a Dynamic NAT I P address range, what is the 2nd step?
Create an access list to use with that pool with the command i p access-list ext 1-nat to name it 1. Then create the I P address range with the command "50 permit ip 192.168.3.0 0.0.0.255 any"
After Dynamic NAT has been set up and the access list has been set up to be used with it, what is the final step?
Add the NAT statement to the inside interface from config mode with the command i p nat inside source list 1-nat pool 1-pool. This will use the access list named 1 and the dynamic pool named 1.
What is a troubleshooting benefit of using Network Time Protocol, or NTP?
All log messages are timestamped, so you can see if there are discontinuities when reviewing log entries. You can then review them in chronological order.
How do you configure NTP on a Cisco device?
From config mode, use the command clock timezone CST -6, for example. On the next line, tell the device to observe daylight savings time with the command clock summer-time CST recurring.
After setting up a Cisco device to use NTP, what is the final step?
From Enable mode, set the local time with the command clock set 15:30:00 18 January 2021.
How can you view the date and time that are configured on a Cisco device?
From enable mode, use the command show clock.
What are the 3 NTP modes that a Cisco device can run in?
1) In client mode, the device gets its time from the NTP server. 2) In server mode, the device provides NTP information to clients. 3) A Cisco device can also perform in both client and server mode at the same time.
How do you configure a Cisco device to be an NTP client?
From config mode, point the device to the NTP server with the command ntp server 192.68.88.1, for example.
How can you check the NTP status of a Cisco device after configuring it to use NTP?
A minute or so after configuring the device, from enable mode run the command show ntp associations.
How can you check the clock configuration to make sure it is correct?
From enable mode use the command show ntp status. It can take between 5 and 10 minutes for a device to synchronize with its assigned NTP server.
How can you make a Cisco router act as an NTP server?
From config mode, use the command ntp master 2. The number 2 is to tell devices in that network to trust that router. The lower that number is, the more trusted the device is.
What are 5 bits of information that are given to a client that is assigned I P information from a DHCP server?
I P address, subnet mask, default gateway, DNS server, and lease time for its I P address.
With Domain Name System, or DNS, what is a Resolver?
Resolvers make requests to higher-level DNS servers on behalf of hosts in a network.
How do you assign an interface to use a DHCP server?
While configuring that interface, use the command i p address dhcp and then no shut the interface.
How can you determine if an interface has gotten its I P address from DHCP?
Use the command show i p interface brief. The results will show the I P addresses assigned to all local interfaces, and also the method that was used to obtain that I P address.
Can a default route be assigned by a DHCP server?
Yes, and that route can be viewed with the command show I P route.
Does DHCP use Layer 3 or Layer 2 connectivity.
It requires Layer 2 connectivity between the requesting host and the DHCP server. In order to facilitate that, unless the default gateway is also the DHCP server, set up a DHCP relay through that router to the distant DHCP server.
How do you set up DHCP relay on a router?
While configuring the outside facing interface, use the command i p helper-address 192.168.88.1, if the remote DHCP server's IP address was 192.168.88.1.
Name 4 things that are often configured to be sent to a centralized syslog server?
Alerts for failed login attempts, STP events, OSPF events, and BGP events.
What is the logging command on Cisco devices that is enabled by default?
Logging console, which can be turned on with that command from config mode if it is not already on.
How can you view syslog messages remotely?
The logging monitor command must be issued from config mode. Once that is enabled and someone is logged in via telnet or SSH, they can then issue the command terminal monitor.
Where are local syslog entries stored and how can they be viewed?
They are stored in RAM by default and can be viewed with the show logging command.
How can you send local syslog entries to a remote location?
From config mode, enter the command logging 192.168.88.2 to send the log entries to that I P address.
What are the 8 syslog message levels, starting with the most severe?
1) 0 and 1 are Alert Emergency that require immediate action because the system is unusable. 2) 2, 3, and 4 are Critical Error Warnings that are Critical Event, Error Event, or Warning Event - in that order. 3) 5 and 6 are Notification Informational. 4) 7 is used for Debugging.
How can you tell the local syslog server which level of events should be sent to the local collection server?
With the logging trap level-name command | 1, in this example only sending notifications that are level 1 or higher.
What is Simple Network Management Protocol, or SNMP?
An Application layer protocol that queries devices for all sorts of information used for trending and troubleshooting purposes.
Give 5 examples of metrics that can be monitored with SNMP.
Port utilization, temperature, RAM, CPU, and storage.
What is a troubleshooting benefit of SNMP notifications?
You can set up SNMP notifications to let you know if there are issues with your devices, often before customers even realize they have a problem.
Is SNMP read-only?
In some instances, SNMP can make changes to equipment remotely to resolve issues.
Give 2 examples of things that SNMP can do to resolve issues.
Shut or no shut ports, and also change VLAN information.
Give 4 characteristics of both FTP and TFTP.
FTP: Uses TCP, Uses authentication, Used on modern devices, and Transfers faster. TFTP: Uses UDP, does not use authentication, Used on old and new devices, and often used for configuration backup files.
In general, what is Quality of Service, or QoS, designed to do?
Identify traffic, mark it, and then enact policies on it. It enables administrators to deal with issues such as jitter, delay, loss, and bandwidth.
What is bandwidth?
A link's speed measured in bits per seconds, or bps.
What is one-way delay?
The time it takes a packet to reach its destination.
What is round-trip delay?
The time it takes a packet to reach a host, and then return to the sending host.
What is Jitter?
When there is a rapid variance in delay, such as 30 ms, 300 ms, 40 ms, 200 ms, etc.
What is Loss?
How many packets are lost between a sending host and a receiving host.
When is traffic acted upon when using QoS?
When it enters or leaves an interface.
What is the Classification portion of QoS?
The process of identifying certain traffic.
What does Differentiated Services, or DiffServ, do in QoS?
Marks traffic into different classes.
In QoS, what is queueing?
Placing marked packets into buckets to be sent at certain times during congestion.
What is a Differentiated Services Code Point, or DSCP, in QoS?
A 6-bit field within an I P header that shows that traffic has already been classified so that a router does not have to then examine and classify that packet.
When DiffServ classifies data, what is used to show its classification?
Either decimal or text can be used to show the classification of that data.
Describe the Expedited Forwarding, or EF, DiffServ classification.
It is 46 in decimal form, or expedited forward in text. It is used for low latency, jitter, and lost packets, such as with VoIP.
Describe the Assured Forwarding DiffServ classification.
It is a collection of 12 different DSCP values. It has 4 queue types, each with 3 levels of drop priority - Low, Medium, and High.
In general, what is the purpose of queueing?
It is used on all networking equipment to store packets that need to traverse busy interfaces.
What is the First-in First-out queueing process?
The first packet in is the first packet to leave.
What are the 3 parts of queueing packet traffic?
A Classifier places packets into a queue. A Scheduler takes packets from the queue for transmission. Prioritization chooses packets from certain queues to send first.
Where should voice traffic be placed when queueing traffic?
Into a low-latency queue so that it doesn't sit in the queue for long, which can affect the quality of voice transmissions.
Give 5 aspects of traffic shaping.
1) Monitors bit rates to keep them within limits. 2) Holds packets in queues. 3) Needs to account for low-latency apps to avoid jitter or delay. 4) Controls Bursting. 5) Is used for Egress only.
Give 6 aspects of traffic policing.
1) Monitors bit rates to keep them within limits. 2) Drops packets. 3) Has a more simple configuration. 4) Has short methods of Bursting. 5) Bidirectional. 6) Discards excess or remarks packets.
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