CCNA Networking Concepts – Part Two
CCNA Networking Concepts – Part One 1
CCNA Networking Concepts – Part One 2
CCNA Networking Concepts – Part One 3
Learning Outcomes
In this module, you will complete the following exercises:
- Exercise 1 – Copper and Fiber Optics Cables
- Exercise 2 – Ethernet Shared Media and Point-to-Point
- Exercise 3 – Concepts of PoE
- Exercise 4 – Interface Configuration Options
- Exercise 5 – Cabling Issues
- Exercise 6 – Examining Methods of Observing Collisions and Other Errors
After completing this lab, you will be able to:
- Know about UTP and STP Cable
- Know about Single-Mode Fiber and Multimode Fiber Cable
- Know about Ethernet Shared Media and Point-to-Point
- Know about Power Over Ethernet
- Perform Duplex Settings
- Perform Speed Settings
- Know about Cable Types and Ports
- Know about Medium Dependent Interface/MDI Crossover
- Identify and Resolve Collisions
- Know about Types of Errors
Exam Objectives
The following exam objectives are covered in this lab:
- 1.3 Compare physical interface and cabling types
- 1.4 Identify interface and cable issues (collisions, errors, mismatch duplex, and/or speed)
Lab Topology
During your session, you will have access to the following lab configuration.
Depending on the exercises, you may or may not use all of the devices, but they are shown here in the layout to get an overall understanding of the topology of the lab.
- NYEDGE1 – (Cisco 2911 – Internet Edge Router 1)
- NYEDGE2 – (Cisco 2911 – Internet Edge Router 2)
- NYWAN1 – (Cisco 2911 – WAN Router)
- NYCORE1 – (Cisco 3750v2 – 24PS – Core Switch 1)
- NYCORE2 – (Cisco 3750v2 – 24PS – Core Switch 2)
- NYACCESS1 – (Cisco 2960-24 – Access Switch 1)
- PLABCSCO01 – (Windows Server 2012 R2 – Cisco Tools Server)
Exercise 1 – Copper and Fiber Optics Cables
Cables are a transport media through which data actually travels. Today, the two most commonly used cable types are copper and fiber optics.
Two types of copper cables are:
- UTP (unshielded twisted-pair cable)
- STP (shielded twisted-pair cable)
Two types of fiber optics cables are:
- Single-Mode Fiber
- Multimode Fiber
In this exercise, you will learn about different cable types used in wired networks.
Learning Outcomes
After completing this exercise, you will be able to:
- Know about UTP and STP Cable
- Know about Single-Mode Fiber and Multimode Fiber Cable
Your Devices
This exercise contains supporting materials for Cisco.
UTP and STP Cable
UTP is a four-pair wire where wires in a pair are twisted around each other. UTP has a slight possibility of canceling interference. Today you have several categories of UTP cables, but the most popular ones are Category 5, Category 5e and Category 6. The difference is in the speed at which they work. Category 5 works up to 100 Mbps, while Cat5e and Cat6 work at a speed of up to 1 Gbps.
STP is also a four-pair wire where wires are twisted and shielded, hence has more of a possibility to cancel interference. Shield cables are sensitive and must be kept intact. STP cables are bigger then UTP cables and they cost more. STP cables are usually used in an environment that has a high amount of electromagnetic interference.
Single-Mode and Multimode Fiber Cable
Since there is a constant growth in bandwidth usage in networks, there is a need to use fiber optics as a medium. Fiber is a medium that uses glass or plastic through which light travels and transmits data. It uses the reflection and refraction characteristics of light.
Fiber-optic cable has two fibers where each fiber is surrounded by layers of protective materials – usually plastic.
There are two types of fiber optics cables, single-mode and multimode. The main difference between them is their speed and distance.
Core diameter is the one that determines how light passes through the cable and this determines characteristics of the cable. Multimode fiber has a larger diametrical core that allows multiple light modes to pass through it. This means that more data can pass through but high dispersion reduces the signal quality . Single-mode has a small diametrical core and only one mode of light can pass through it, but it can travel further than multimode cables.
Single-mode is used for long distances that require more bandwidth, for example, on an ISP side, telecom companies and cable television providers.
Multimode optical fiber cable is used for short distances, for example, in LAN networks.
Exercise 2 – Ethernet Shared Media and Point-to-Point
Ethernet is a standard that defines cables, connectors , and protocols. It is a standard for the first two layers of the OSI reference system. In the previous exercise, you learned about different cable types, which are actually Ethernet links. Ethernet technology is mostly used in local area networks (LAN).
In this exercise, you will learn about the difference between ethernet shared media and point to point.
Learning Outcomes
After completing this exercise, you will be able to:
- Know about Ethernet Shared Media and Point-to-Point
Your Devices
This exercise contains supporting materials for Cisco.
Ethernet Shared Media and Point-to-Point
In an Ethernet LAN, multiple computers are connected to the same device Communication to the device is made using half duplex and full duplex methods.
Older network devices used a LAN HUB. It is a device that has multiple ethernet ports where you connect your devices. Hubs are different from modern switches because they use different logic to forward data.
When data comes to a hub, the hub sends that data to all other ports. Hubs have no MAC addresses and ethernet frames. Hence there could be issues if multiple devices try to send data at the same time . It is actually a Layer 1 device. This leads to a collision and devices are unable to send data to a destination device. In this scenario, devices are said to be on shared media.
If switches are used instead of a hub, no collision can occur, because a switch is a layer 2 device and doesn’t send the incoming data to all other ports. Two devices connected over a switch are on a separate point-to-point link. If you have multiple devices on the same switch that need to communicate, they actually are building logical point-to-point links. Multiple devices can now send/receive data at the same time without any collisions.
You will learn more about collisions and half /full duplex methods in the following exercises.There are no screenshot items for this exercise.
Exercise 3 – Concepts of PoE
The concept behind Power over Ethernet (PoE) is to give power to devices connected to a switch port with PoE capability. In this exercise, you will learn how power is transmitted over the ethernet.
Learning Outcomes
After completing this exercise, you will be able to:
- Know about Power Over Ethernet
Your Devices
This exercise contains supporting materials for Cisco.
Power Over Ethernet
PoE refers to transmitting electrical power to a device (usually IP phone or access point) over a standard copper cable. Power is transmitted along with the data.
There are two standards for power over Ethernet. An 802.3af (PoE) and an 802.3at (PoE+), which transmits more power. Both standards describe how power is delivered to a given device.
Exercise 4 – Interface Configuration Options
An interface is an entity through which network devices are interconnected. All interfaces exist within the Physical and Data Link layers of the OSI model, although some interfaces do have features in higher layers as well.
In this exercise, you will examine the configuration parameters that affect the connectivity of interfaces within the first two layers of the OSI model.
Learning Outcomes
After completing this exercise, you will be able to:
- Perform Duplex Settings
- Perform Speed Settings
Your Devices
You will be using the following devices in this lab. Please power these on now.
- NYEDGE1 – (Cisco 2911 – Internet Edge Router 1)
- NYWAN1 – (Cisco 2911 – WAN Router)
- NYCORE1 – (Cisco 3750v2 – 24PS – Core Switch 1)
- NYACCESS1 – (Cisco 2960-24 – Access Switch 1)
Task 1 – Duplex Settings
The duplex setting of an interface configures whether both ends of the connection can provide communication simultaneously or if the devices on each end will have to communicate one at a time. All modern network equipment supports fully bi-directional, or more correctly, full duplex communication. However, half duplex communication can be configured if you are required to interface with older equipment.
In this task, you will examine and configure the duplex settings between the NYCORE1 switch and the NYEDGE1 router.
Step 1
Connect to the NYCORE1 switch and examine the capabilities of the FastEthernet 1/0/2 interface, which connects to the NYACCESS1 switch. To do this, execute the following command:
NYCORE1#
show interface fastethernet 1/0/2 capabilities
Press Enter.
You will see the following output:
NYCORE1#show interface fastethernet 1/0/1 capabilities
FastEthernet1/0/1
Model: WS-C3750V2-24PS
Type: 10/100BaseTX
Speed: 10,100,auto
Duplex: half,full,auto
Trunk encap. type: 802.1Q,ISL
Trunk mode: on,off,desirable,nonegotiate
Channel: yes
Broadcast suppression: percentage(0-100)
Flowcontrol: rx-(off,on,desired),tx-(none)
Fast Start: yes
QoS scheduling: rx-(not configurable on per port basis),
tx-(4q3t) (3t: Two configurable values and one fixed.)
CoS rewrite: yes
ToS rewrite: yes
UDLD: yes
Inline power: yes
SPAN: source/destination
PortSecure: yes
Dot1x: yes
NYCORE1#
Look for the Duplex capabilities in the output. You will notice that the capabilities of this port include the following settings: half, full and auto.Note: A duplex setting of auto will allow devices to negotiate the duplex settings of the link. If both ends can support full duplex, then the negotiation will result in full duplex being chosen.
Step 2
Next, determine which of the three duplex settings has been configured on this interface. Examine the portion of the running configuration that pertains to the FastEthernet 1/0/2 interface. To avoid viewing the whole running configuration and searching for the configuration of the interface in question, issue the following command to see only the configuration of the specific interface:
NYCORE1#
show run interface fastethernet 1/0/2
Press Enter.
You will see the following output:
NYCORE1#show run interface fastethernet 1/0/2
Building configuration...
Current configuration : 36 bytes
!
interface FastEthernet1/0/2
end
NYCORE1#
Notice that there are no configuration parameters implemented for the specific interface. The default duplex setting for a Cisco device is auto.Note: The default settings of interfaces are not explicitly included in the running configuration of Cisco devices. This is also the case for duplex settings. When no duplex parameters are present, the duplex setting is the default of auto.
You can confirm this by displaying the duplex settings of all the interfaces of the switch with the following command:
NYCORE1#
show interface status
Press Enter.
The output will be as follows:
NYCORE1#show interface status
Port Name Status Vlan Duplex Speed Type
Fa1/0/1 connected 1 a-full a-100 10/100BaseTX
Fa1/0/2 connected 1 a-full a-100 10/100BaseTX
Fa1/0/3 notconnect 1 auto auto 10/100BaseTX
Fa1/0/4 notconnect 1 auto auto 10/100BaseTX
!<-- Output Omitted -->
Gi1/0/1 notconnect 1 auto auto Not Present
Gi1/0/2 notconnect 1 auto auto Not Present
NYCORE1#
All of the interfaces that have a status of notconnect show a duplex value of auto. This means that they are configured as auto, which, as mentioned before, is the default configuration. The connected interfaces have a duplex value of a-full. This is because they are currently operating in full duplex mode via negotiation because their duplex configuration is auto.
Step 3
Now examine the current duplex operation of the FastEthernet 1/0/2 with the following command:
NYCORE1#
show interface fastethernet 1/0/2
Press Enter.
You will see the following output:
NYCORE1#show interface fastethernet 1/0/2
FastEthernet1/0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 8875.56bb.9218 (bia 8875.56bb.9218)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
!<-- Output Omitted -->
NYCORE1#
Look for the line indicating the duplex setting. From the above output, you will see that the interface is currently functioning in Full-duplex mode.
Step 4
Next, you will determine what the duplex settings are on the other end of this link. Connect to the NYEDGE1 router and examine the duplex setting of the GigabitEthernet 0/0 interface by entering the following command:
NYEDGE1#
show running-config interface gigabitEthernet 0/0
Press Enter.
You will see the following output:
NYEDGE1#show running-config interface gigabitEthernet 0/0
Building configuration...
Current configuration : 76 bytes
!
interface GigabitEthernet0/0
no ip address
duplex auto
speed auto
end
NYEDGE1#
You will notice here that the duplex configuration is set to auto.Note: Unlike switches, the default duplex configuration is displayed in the running configuration for routers.
So you can conclude from the commands that you executed on these two devices that both ends of the link have duplex settings of auto, and the duplex negotiation has resulted in the operation of a full duplex link.
Step 5
In this step, you will observe what will happen if you change the duplex configuration of the GigabitEthernet 0/0 interface on the NYEDGE1 router to half duplex. To do so, execute the following commands (press Enter after each command):
NYEDGE1#
configure terminal
NYEDGE1(config)#
interface GigabitEthernet 0/0
NYEDGE1(config-if)#
duplex half
NYEDGE1(config-if)#
exit
NYEDGE1(config)#
exit
You will see the following output:
NYEDGE1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NYEDGE1(config)#interface GigabitEthernet 0/0
NYEDGE1(config-if)#duplex half
NYEDGE1(config-if)#
*Sep 22 18:47:51.167: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to down
*Sep 22 18:47:53.571: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up
NYEDGE1(config-if)#exit
NYEDGE1(config)#exit
NYEDGE1#
Notice that the interface went down, and a few seconds later was brought back up. The link stopped functioning as a full duplex link and was renegotiated to function as a half duplex link.Note: When the duplex settings are set to auto on one end and either full or half duplex on the other end of the link, negotiation occurs once again. However, in this case, the device set to auto will always revert to whatever duplex configuration the other end has.
Step 6
Examine the current duplex operation of the GigabitEthernet 0/0 interface on the NYEDGE1 router to verify that it is functioning in half duplex:
NYEDGE1#
show interface gigabitEthernet 0/0
Press Enter.
You will see the following output:
NYEDGE1#show interface gigabitEthernet 0/0
GigabitEthernet0/0 is up, line protocol is up
Hardware is CN Gigabit Ethernet, address is 7426.ac67.0c70 (bia 7426.ac67.0c70)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00NYACCESS1#show interface fastethernet 0/24
!<-- Output Omitted -->
NYEDGE1#
You should be able to confirm from the above output that the link is functioning in half duplex.
Step 7
Next, you will observe what happens when there is a duplex mismatch on the link. This occurs when one end of the link is explicitly configured as full duplex and the other as half duplex. Connect to the NYCORE1 switch and configure the FastEthernet 1/0/1 interface duplex settings to full duplex by issuing the following commands (press Enter after each command):
NYCORE1#
configure terminal
NYCORE1(config)#
interface fastethernet 1/0/1
NYCORE1(config-if)#
duplex full
NYCORE1(config-if)#
exit
NYCORE1(config)#
exit
You will see the following output:
NYCORE1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NYCORE1(config)#interface fastethernet 1/0/1
NYCORE1(config-if)#duplex full
NYCORE1(config-if)#exit
NYCORE1(config)#exit
NYCORE1#
*Mar 1 00:19:15.488: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0/1, changed state to down
*Mar 1 00:19:16.495: %LINK-3-UPDOWN: Interface FastEthernet1/0/1, changed state to down
*Mar 1 00:19:23.768: %LINK-3-UPDOWN: Interface FastEthernet1/0/1, changed state to up
*Mar 1 00:19:24.338: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet1/0/1 (not half duplex), with NYEDGE1 GigabitEthernet0/0 (half duplex).
*Mar 1 00:19:24.774: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0/1, changed state to up
*Mar 1 00:19:25.337: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet1/0/1 (not half duplex), with NYEDGE1 GigabitEthernet0/0 (half duplex).
*Mar 1 00:19:26.335: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on FastEthernet1/0/1 (not half duplex), with NYEDGE1 GigabitEthernet0/0 (half duplex).
You can see the syslog messages begin to appear that indicate that there is a duplex mismatch. The state of interface FastEthernet 1/0/1 is actually up. However, the link is non-functional.
You should see similar syslog messages appear on the console of NYEDGE1 as well.
Step 8
Restore connectivity by changing the half duplex configuration on the NYEDGE1 router to full duplex. This will result in a link that is explicitly configured as full duplex at both ends. Connect to NYEDGE1 and enter the following commands (press Enter after each command):
NYEDGE1#
configure terminal
NYEDGE1(config)#
interface gigabitEthernet 0/0
NYEDGE1(config-if)#
duplex full
NYEDGE1(config-if)#
exit
NYEDGE1(config)#
exit
You will see the following output:
NYEDGE1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NYEDGE1(config)#interface gigabitEthernet 0/0
NYEDGE1(config-if)#duplex full
NYEDGE1(config-if)#exit
NYEDGE1(config)#exit
NYEDGE1#
*Sep 22 19:00:16.143: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to down
*Sep 22 19:00:17.135: %SYS-5-CONFIG_I: Configured from console by console
*Sep 22 19:00:18.591: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up
NYEDGE1#
Notice the syslog messages that indicate that the link has gone down and has come back up. Notice also that the syslog duplex mismatch messages have ceased.
You have successfully configured the duplex settings.Leave the devices in their current states and continue on to the next task.
Task 2 – Speed Settings
The speed settings of an interface functions in much the same way as the duplex settings, except instead of affecting uni-directional or bi-directional communication, it affects the speed of the link. The speed refers to the speed of the Ethernet link such as:
- 10 Mbps
- 100 Mbps
- 1000 Mbps
- 10 Gbps
- 40 Gbps
In this task, you will examine and configure speed settings between several network devices.
Step 1
Connect to the NYCORE1 switch and examine the capabilities of the FastEthernet 1/0/2 interface. Examine the lab diagram to see which device connects to this interface. To do this, execute the following command:
NYCORE1#
show interface fastethernet 1/0/2 capabilities
Press Enter.
You will see the following output:
NYCORE1#show interface fastethernet 1/0/2 capabilities
FastEthernet1/0/2
Model: WS-C3750V2-24PS
Type: 10/100BaseTX
Speed: 10,100,auto
Duplex: half,full,auto
Trunk encap. type: 802.1Q,ISL
Trunk mode: on,off,desirable,nonegotiate
!<-- Output Omitted -->
NYCORE1#
The speed capabilities of this interface are 10, 100, and auto.
Step 2
Examine the current speed configuration of the FastEthernet 1/0/2 interface. This time, you will use the “|” modifier to filter out the output:
NYCORE1#
show interface status | include 1/0/2
Press Enter.
You will see the following output:
NYCORE1# show interface status | include 1/0/2
Fa1/0/2 connected 1 a-full a-100 10/100BaseTX
Fa1/0/20 notconnect 1 auto auto 10/100BaseTX
Fa1/0/21 notconnect 1 auto auto 10/100BaseTX
Fa1/0/22 connected 1 a-full a-100 10/100BaseTX
Fa1/0/23 connected 1 a-full a-100 10/100BaseTX
Fa1/0/24 connected 1 a-full a-100 10/100BaseTX
Gi1/0/2 notconnect 1 auto auto Not Present
NYCORE1#
Note: Although the 1/0/2 string that was inputted was not unique, it did minimize the output to a more manageable size.
Interface FastEthernet 1/0/2 has a speed indicator of a-100. This means the speed has been auto-negotiated to 100 Mbps.
Step 3
Examine the other end of the link. In Step 1, you were asked to look at the lab diagram and determine which devices are connected to the other end of the link. You will have discovered that this is the GigabitEthernet 0/0 interface of the NYWAN1 router.
Connect to NYWAN1. Specifically, take a look at the interface parameters:
NYWAN1#
show interface gigabitethernet 0/0
Press Enter.
You will see the following output:
NYWAN1#show interface gigabitethernet 0/0
GigabitEthernet0/0 is up, line protocol is up
Hardware is CN Gigabit Ethernet, address is 18e7.28e9.0690 (bia 18e7.28e9.0690)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
!<-- Output Omitted -->
NYWAN1#
From its name, you already know that this interface is capable of functioning at 1000Mbps. However, from the above output, you see that the speed is at 100Mbps. This is to be expected because when two devices are configured to auto-negotiate their speed, they use the highest mutually available speed, which in this case, is 100Mbps.Note: Routers do not have the same show commands to display interface status as switches do. If you attempt to issue the show interface status command on a router, no output will result. Try it and see.
Step 4
In this step, you will explicitly configure the GigabitEthernet 0/0 interface of the NYWAN1 router to use a speed of 1000 Mbps, and you will examine the results. Issue the following commands (press Enter after each command). Use the ? as shown below to understand your options more clearly:
NYWAN1#
configure terminal
NYWAN1(config)#
interface gigabitethernet 0/0
NYWAN1(config-if)#
speed ?
NYWAN1(config-if)#
speed 1000
NYWAN1(config-if)#
exit
You will see the following output:
NYWAN1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NYWAN1(config)#interface gigabitethernet 0/0
NYWAN1(config-if)#speed ?
10 Force 10 Mbps operation
100 Force 100 Mbps operation
1000 Force 1000 Mbps operation
auto Enable AUTO speed configuration
NYWAN1(config-if)#speed 1000
NYWAN1(config-if)#exit
NYWAN1(config)#
*Sep 14 17:30:58.203: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to down
*Sep 14 17:30:59.203: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down
As expected, syslog messages indicate that the link is now down. This is because the FastEthernet 1/0/2 interface of the NYCORE1 switch is only capable of up to 100 Mbps and cannot auto-negotiation to 1000 Mbps.
Step 5
Next, you will explicitly configure both ends of the link to function at 10 Mbps eliminating the negotiation of speeds. Configure the GigabitEthernet 0/0 interface of the NYWAN1 accordingly.
Type the following commands (press Enter after each command):
NYWAN1(config)#
interface gigabitethernet 0/0
NYWAN1(config-if)#
speed 10
NYWAN1(config-if)#
exit
You will see the following output:
NYWAN1(config)#interface gigabitethernet 0/0
NYWAN1(config-if)#speed 10
NYWAN1(config-if)#exit
NYWAN1(config)#
*Sep 14 17:34:54.023: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
*Sep 14 17:34:55.179: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up
NYWAN1(config)#
Because the other end of the link is currently set to auto-negotiate speed, the link auto-negotiates to 10 Mbps.
Step 6
Connect to NYCORE1 and explicitly configure interface FastEthernet 1/0/2 to function at 10 Mbps as follows.
Type the following commands (press Enter after each command):
NYCORE1#
configure terminal
NYCORE1(config)#
interface fastethernet 1/0/2
NYCORE1(config-if)#
speed 10
NYCORE1(config-if)#
exit
NYCORE1(config)#
exit
The output will be as follows:
NYCORE1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NYCORE1(config)#interface fastethernet 1/0/2
NYCORE1(config-if)#speed 10
NYCORE1(config-if)#exit
NYCORE1(config)#
*Mar 1 00:46:42.684: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0/2, changed state to down
*Mar 1 00:46:44.697: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0/2, changed state to up
NYCORE1(config)#exit
NYCORE1#
Notice the interface goes down and comes back up.
Step 7
Next, you will verify the configuration and the operation of the link as follows:
NYCORE1#
show interface status | include 1/0/2
Press Enter.
You will see the following output:
NYCORE1#show interface status | include 1/0/2
Fa1/0/2 connected 1 a-full 10 10/100BaseTX
Fa1/0/20 notconnect 1 auto auto 10/100BaseTX
Fa1/0/21 notconnect 1 auto auto 10/100BaseTX
Fa1/0/22 connected 1 a-full a-100 10/100BaseTX
Fa1/0/23 connected 1 a-full a-100 10/100BaseTX
Fa1/0/24 connected 1 a-full a-100 10/100BaseTX
Gi1/0/2 notconnect 1 auto auto Not Present
NYCORE1#
The speed here is indicated by a number 10. This shows that the speed is explicitly configured and is not negotiated. The state of FastEthernet 1/0/2 is connected. Therefore the interface is up, and it is functioning at a speed of 10 Mbps.
You have successfully configured speed settings.
Exercise 5 – Cabling Issues
Errors on an interface can often be caused by faulty or incorrect cable installations. This is true for both copper and fiber media. A bad copper cable connection, a slightly too long UTP cable, or a bend of a fiber optic cable that has a slightly-too-small radius could be some of the reasons why errors occur on an interface.
In this exercise, you will examine the types of ports that exist on Cisco devices, what kinds of media they will accept, and some configurations that affect the types of cables that you can use.
Learning Outcomes
After completing this exercise, you will be able to:
- Know about Cable Types and Ports
- Know about Medium Dependent Interface/MDI Crossover
Your Devices
You will be using the following devices in this lab. Please power these on now.
- NYCORE1 – (Cisco 3750v2 – 24PS – Core Switch 1)
Task 1 – Cable Types and Ports
Different types of interfaces on a device accept different types of cables. In this task, you will examine the available types of interfaces on a switch and the types of media that can be connected to them.
Step 1
Connect to the NYCORE1 device and take a look at the status of all the interfaces on the switch. Issue the following command:
NYCORE1#
show interface status
Press Enter.
You will see the following output:
NYCORE1#show interface status
Port Name Status Vlan Duplex Speed Type
Fa1/0/1 notconnect 1 auto auto 10/100BaseTX
Fa1/0/2 connected 1 a-full 10 10/100BaseTX
Fa1/0/3 notconnect 1 auto auto 10/100BaseTX
Fa1/0/4 notconnect 1 auto auto 10/100BaseTX
Fa1/0/5 notconnect 1 auto auto 10/100BaseTX
Fa1/0/6 notconnect 1 auto auto 10/100BaseTX
Fa1/0/7 notconnect 1 auto auto 10/100BaseTX
Fa1/0/8 notconnect 1 auto auto 10/100BaseTX
Fa1/0/9 notconnect 1 auto auto 10/100BaseTX
Fa1/0/10 notconnect 1 auto auto 10/100BaseTX
Fa1/0/11 notconnect 1 auto auto 10/100BaseTX
Fa1/0/12 notconnect 1 auto auto 10/100BaseTX
Fa1/0/13 notconnect 1 auto auto 10/100BaseTX
Fa1/0/14 notconnect 1 auto auto 10/100BaseTX
Fa1/0/15 notconnect 1 auto auto 10/100BaseTX
Fa1/0/16 notconnect 1 auto auto 10/100BaseTX
Fa1/0/17 notconnect 1 auto auto 10/100BaseTX
Fa1/0/18 notconnect 1 auto auto 10/100BaseTX
Fa1/0/19 notconnect 1 auto auto 10/100BaseTX
Fa1/0/20 notconnect 1 auto auto 10/100BaseTX
Fa1/0/21 notconnect 1 auto auto 10/100BaseTX
Fa1/0/22 connected 1 a-full a-100 10/100BaseTX
Fa1/0/23 connected 1 a-full a-100 10/100BaseTX
Fa1/0/24 connected 1 a-full a-100 10/100BaseTX
Gi1/0/1 notconnect 1 auto auto Not Present
Gi1/0/2 notconnect 1 auto auto Not Present
NYCORE1#
Observe the Type column. Interfaces FastEthernet 1/0/1 through to 1/0/24 have a type of 10/100BaseTX. This indicates a copper connection via an RJ-45 port.
Interfaces GigabitEthernet 1/0/1 and 1/0/2 indicate a Not Present in the Type column. This is a Small Form-factor Port or SFP. This type of port accepts a module that will allow for different types of media, depending on the module used. In most cases, an SFP module that accepts fiber optic cables is used.Note: Use your favorite search engine to research SFP ports, SPF modules, and media types further.
Task 2 – Medium Dependent Interface/MDI Crossover
There are two types of Ethernet copper cables that use the RJ-45 connector: a straight through cable and a crossover cable. Traditionally, crossover cables are used between devices of the same type, such as switch to switch or router to router. Straight-through cables are used for different device types such as a router to switch or switch to end device.
In order to avoid mistakes by using the wrong type of cable for the wrong pair of devices, the MDI/MDIX functionality has been introduced to network devices. This feature automatically and electronically changes the pin outs of the appropriate switch ports to successfully connect devices regardless of whether a crossover or a straight through cable is used.
This functionality can be activated or deactivated and, if misconfigured, can result in a loss of connectivity. Cisco devices have MDIX on by default.
Step 1
Connect to the NYCORE1 switch and disable the MDIX functionality on the FastEthernet 1/0/22 interface with the following commands (press Enter after each command):
NYCORE1#
configure terminal
NYCORE1(config)#
interface fastethernet 1/0/22
NYCORE1(config-if)#
no mdix auto
NYCORE1(config-if)#
exit
NYCORE1(config)#
exit
You will see the following output:
NYCORE1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NYCORE1(config)#interface fastethernet 1/0/22
NYCORE1(config-if)#no mdix auto
NYCORE1(config-if)#
*Mar 1 02:14:01.529: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0/22, changed state to down
*Mar 1 02:14:02.535: %LINK-3-UPDOWN: Interface FastEthernet1/0/22, changed state to down
NYCORE1(config-if)#exit
NYCORE1(config)#exit
NYCORE1#
The change resulted in the link going down.Note: According to Cisco, the only time that a medium mismatch will cause a link to go down is when MDIX is deactivated on both ends, and the incorrect cable type is used to connect the devices. Otherwise, even if one end of the link is configured without MDIX, the autoconfiguration on the other end will resolve the cable type mismatch. However, in this lab topology, due to the nature of the platform, the link goes down even if one side is still configured with auto MDIX. Research this topic further using your favorite search engine to find out more.
Exercise 6 – Examining Methods of Observing Collisions and Other Errors
Some of the most difficult types of faults on a network to diagnose and correct are those that are of an intermittent nature or those that cause degradation to network performance rather than a complete loss of connectivity. Many of these types of faults can be traced back to errors on interfaces, including collisions and frame errors.
Many of these errors can be diagnosed at the interface level. In this exercise, you will examine and diagnose errors that are found on interface counters on a switch and will decide on appropriate action to rectify these errors.
Learning Outcomes
After completing this exercise, you will be able to:
- Identify and Resolve Collisions
- Know about Types of Errors
Your Devices
You will be using the following devices in this lab. Please power these on now.
- NYCORE1 – (Cisco 3750v2 – 24PS – Core Switch 1)
Task 1 – Collisions
Collisions occur on a network segment when two or more devices attempt to access the medium simultaneously. Although there are mechanisms in place that detect and manage such events, an excessive number of collisions could cause undesired network degradation. In this task, you will identify and resolve network collisions.Note: Switches, as opposed to hubs, are used to isolate each port to a collision domain of its own. This essentially eliminates all collisions and makes high-speed Ethernet networks much more efficient. If, however, collisions are detected on a switch port, it is a sign that something is incorrectly configured or that users are misusing the network resources. Such a situation must be investigated.
Step 1
First, you will determine the number of collisions that have been detected by the NYCORE1 switch on the FastEthernet 1/0/2 interface.
Connect to NYCORE1 switch and issue the following command:
NYCORE1#
show interface fastethernet 1/0/2
Press Enter.
You will see the following output:
NYCORE1#show interface fastethernet 1/0/2
FastEthernet1/0/2 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 08cc.68bf.a684 (bia 08cc.68bf.a684)
MTU 1500 bytes, BW 10000 Kbit/sec, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:14, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
371 packets input, 41995 bytes, 0 no buffer
Received 67 broadcasts (67 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 67 multicast, 0 pause input
0 input packets with dribble condition detected
2081 packets output, 161882 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
NYCORE1#
Look for the collisions counter. According to the above output, there are no collisions detected on this interface. Your output should look similar.
Step 2
If collisions were detected, you would first have to determine if these counters are recent or if they are old. To do this, you can reset the counters on the interface and display them again in a few seconds to determine if the collisions are currently occurring.
To clear all the counters from the interface, type the following:
NYCORE1#
clear counters fastEthernet 1/0/2
Press Enter.
Clear “show interface” counters on this interface [confirm]
Press Enter.
You will see the following output:
NYCORE1#clear counters fastEthernet 1/0/2
Clear "show interface" counters on this interface [confirm]
NYCORE1#
*Mar 1 01:13:35.771: %CLEAR-5-COUNTERS: Clear counter on interface FastEthernet1/0/2 by console
NYCORE1#
A syslog message informs you that the counters have been cleared, address table to be repopulated, as seen in the above example.
Step 3
Wait for a few seconds and then view the interface counters once again:
NYCORE1#
show interface fastethernet 1/0/2
Press Enter.
You will see the following output:
NYCORE1#show interface fastethernet 1/0/2
FastEthernet1/0/2 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 08cc.68bf.a684 (bia 08cc.68bf.a684)
MTU 1500 bytes, BW 10000 Kbit/sec, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:28, output 00:00:01, output hang never
Last clearing of "show interface" counters 00:03:20
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
24 packets input, 2708 bytes, 0 no buffer
Received 4 broadcasts (4 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 4 multicast, 0 pause input
0 input packets with dribble condition detected
138 packets output, 10194 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
NYCORE1#
Even though there are no collisions to show in the above output, you can see that other counters have been reset and have begun counting again from zero. You can use the up arrow to show the counters repeatedly and to view the counters as they increase.
Other Types of Errors
This same process can be used to view other types of errors as well. Some counters from the above output that you may find useful are:
- Runts – frames that are smaller than 64 bytes which are usually results of collisions
- CRC errors – frames that have not passed the frame check sequence test in the trailer of the Ethernet frame
- Giants – frames that are larger than the maximum size of 1500 bytes
Note: Use your favorite search engine to further research interface counters and errors.
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