What are Modular Transceivers?
Mod 3.1 Network Interfaces
Objective 1.5 | 5.2
- different types of fiber optic and copper connections
SFP/SFP+
(1) Small form-factor pluggable (SFP) - transceivers use LC connectors and support Gigabit Ethernet data rates
(2) Enhanced SFP (SFP+) - updated specification to support 10 GbE but still uses the LC form factor
QSFP/QSFP+
(1) Quad small form-factor pluggable (QSFP) - transceiver form factor that supports 4 x 1 Gbps links, typically aggregated to a single 4 Gbps channel
(2) Enhanced quad small form-factor pluggable (QSFP+) - designed to support 40 GbE by provisioning 4 x 10 Gbps links, typically used with parallel fiber and multi-fiber push-on (MPO), Wavelength Division Multiplexing (WDM) Ethernet standards
Modular transceivers are essential components in networking for connecting various types of media.
What are the three ways fiber mode?
Mod 3.1 Network Interfaces
Objective 1.5 | 5.2
(1) Duplex uses two strands for transmit (Tx) and receive (Rx)
(2) Parallel uses multiple strands (typically eight or twenty) to implement Tx and Rx channels
(3) Wavelength Division Multiplexing uses either a single bidirectional strand or dual unidirectional strands to implement multiple channels, distinguished by wavelengths
Each method utilizes different configurations of fiber strands for transmitting and receiving data.
What is Transceiver Signal Strength Issues?
Mod 3.1 Network Interfaces
Objective 1.5 | 5.2
- Attenuation can be tested using an optical source and optical power meter (or fiber light meter)
Optical link budget: loss budget, is the amount of loss suffered by all components along a fiber transmission path
(1) Attenuation - loss over the length of the cable, based on fiber type and the wavelength used, Single mode loss of up to 0.4 dB/km, multimode 0.8 dB/km to 3 dB/km
(2) Connectors - Each connector in the path incurs a loss, usually assumed to be 0.75 dB
(3) Splices - Additional splices in the cable are budgeted at around 1 dB for mechanical and 0.3 dB for fusion
Single mode loss can be up to 0.4 dB/km, while multimode loss ranges from 0.8 dB/km to 3 dB/km.
Ethernet headers Format?
Mod 3.1 Network Interfaces
Objective 1.5 | 5.2
Ethernet headers Format?
Ethernet headers: encapsulates the payload from higher layer protocols within a protocol data unit (PDU) called a frame, basic format of an Ethernet frame is Ethernet Header
Preamble:
- start frame delimiter (SFD), clock synchronization and as part of the CSMA/CD protocol to identify collisions
- 8 bytes of alternating 1s and 0s w/ SFD being two consecutive 1s at the end
EtherType:
- 2-byte EtherType field is usually used to indicate the type of protocol in the frame payload
Error Checking:
- 32-bit (4-byte) checksum called a cyclic redundancy check (CRC) or frame check sequence (FCS)
- calculated based on the contents of the frame, receiving node performs the same calculation, if it matches, accepts the frame
The basic format of an Ethernet frame is the Ethernet Header.
What is the Media Access Control Address Format?
Mod 3.1 Network Interfaces
Objective 1.5 | 5.2
- source and destination addresses in a frame are 48-bit Media Access Control (MAC) identifiers
- displayed as six groups of two hexadecimal digits with colon or hyphen separators or no separators
Burned-in Addresses:
- IEEE gives each network adapter manufacturer a range of numbers, and the manufacturer hard codes every interface produced with a unique number from their range
- First six hex digits (3 bytes or octets), also known as the organizationally unique identifier (OUI), identify the manufacturer of the adapter. The last six digits are a serial number
Can be separated by colons, hyphens, or have no separators.
Broadcast, Multicast, Unicast?
Mod 3.1 Network Interfaces
Objective 1.5 | 5.2
Broadcast: Packet or frame addressed to all hosts on a local network segment, subnet, or broadcast domain. Routers do not ordinarily forward broadcast traffic. The broadcast address of IP is one where the host bits are all set to 1; at the MAC layer it is the address ff:ff:ff:ff:ff:ff.
Multicast: A packet addressed to a selection of hosts (in IP, those belonging to a multicast group).
Unicast: A packet addressed to a single host. If the host is not on the local subnet, the packet must be sent via one or more routers.
Broadcast Domain: Network segment in which all nodes receive the same broadcast frames at layer 2
Routers do not ordinarily forward broadcast traffic. The broadcast address of IP is one where the host bits are all set to 1; at the MAC layer it is the address ff:ff:ff:ff:ff:ff.
Hubs
Mod 3.2 Ethernet Switches
Objective 1.2 | 2.2
Hubs
- Ethernet networks are implemented so that each end system node is wired to a central intermediate system
- Multiport repeater so that every port receives transmissions sent from any other port
- Physical layer
End system interface
- medium dependent interface (MDI)
- interface on the hub is referred to as MDI crossover (MDIX)
This structure allows for organized communication within the network.
Bridges
Mod 3.2 Ethernet Switches
Objective 1.2 | 2.2
Bridges
- An Ethernet bridge works at the Data Link layer (layer 2) to establish separate physical network segments while keeping all nodes in the same logical network
- MAC Address Table: Data store on a switch that keeps track of the MAC addresses associated with each port. As the switch uses a type of memory called Content Addressable Memory (CAM), this is sometimes called the CAM table
- If no record of the MAC address exists or the frame is a broadcast or multicast, then the bridge floods the frame to all segments except for the source segment (acting like a hub)
It establishes separate physical network segments while keeping all nodes in the same logical network.
Switches
Mod 3.2 Ethernet Switches
Objective 1.2 | 2.2
Switches
- Hubs and bridges are replaced with switches
- Gigabit Ethernet and faster can only be deployed using switches
- Each switch port is a separate collision domain
- switch establishes a point to point link between any two network nodes (Full-duplex)
Full-duplex
- Network link that allows interfaces to send and receive simultaneously
Microsegmentation
- Method of dividing networks to isolate workloads and the infrastructure that supports them from other workloads
Switches provide more efficient data handling compared to hubs and bridges.
What are Ethernet Switch Types?
Mod 3.2 Ethernet Switches
Objective 1.2 | 2.2
Ethernet Switch Types
Unmanaged versus managed:
(1) unmanaged - SOHO network, switch functionality might also be built into an Internet router/modem
(2) managed - corporate network, switch settings can be configured
Stackable - Switches that can be connected together and operate as a group, managed as a single unit
Modular versus fixed - A fixed switch comes with a set number of ports that cannot be changed or upgraded configured with different numbers and types of ports
Desktop versus rack-mounted - Simple unmanaged switches with five or eight ports might be supplied as small freestanding units that can be placed on a desktop
Unmanaged switches are simpler and typically used in smaller networks, while managed switches offer more control and features for larger networks.
What is Link Aggregation and NIC Teaming?
Mod 3.3 Switch Port Configuration
Objective 2.2 | 5.3
Link Aggregation and NIC Teaming
Link aggregation: means combining two or more separate cabled links into a single logical channel, uplink between two switches or between a switch and a router or between two routers, provide redundancy
- Link aggregation group (LAG): EEE 802.3ad/802.1ax standard. 802.3ad bonded interfaces
- Link Aggregation Control Protocol (LACP): used to detect configuration errors and recover from the failure of one of the physical links
NIC Teaming: Two or more NIC aggregated into a single channel link for fault tolerance and increased throughput. Also known as NIC bonding.
This can occur between switches, a switch and a router, or between two routers, providing redundancy.
What is Maximum Transmission Unit (MTU)?
Mod 3.3 Switch Port Configuration
Objective 2.2 | 5.3
- Standard Ethernet frame has a maximum length of 1,518 bytes, 18-byte header
6-byte destination and source MAC address fields.
4-byte error checking field.
2-byte EtherType field - Upper limit of the payload referred to as MTU
- Jumbo Frame: supports a data payload of up to 9,216 bytes
MTU refers to the upper limit of the payload in a network frame.
What is Spanning Tree Protocol?
Mod 3.3 Switch Port Configuration
Objective 2.2 | 5.3
Spanning Tree Protocol
- Bridges or switches to organize themselves into a hierarchy and block loops
This protocol helps prevent network loops in Ethernet networks.
What is Spanning Tree Protocol Configuration?
Mod 3.3 Switch Port Configuration
Objective 2.2 | 5.3
Spanning Tree Protocol Configuration
- Administrator can set the priority value to predetermine root bridge selection
- Root Bridge Selection: In Spanning Tree Protocol (STP), the process and metrics that determine which bridge or switch will be identified as root. Selection of an inappropriate root device can cause performance and security issues
This setting influences which bridge will be designated as the root bridge.
What does Power Over Ethernet (PoE) refer to?
Mod 3.3 Switch Port Configuration
Objective 2.2 | 5.3
Power Over Ethernet
- Supplying electrical power from a switch port over ordinary data cabling to a connected powered device (PD), such as a VoIP handset, IP camera, or wireless access point.
Examples of powered devices include VoIP handsets, IP cameras, and wireless access points.
Hardware Failure Issues
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Power Issues
- surge and spikes: damage devices
- under voltage: lock up or reboot
- power failures: down everything + lights
Network Adapters, Switches, Routers, Modem = Cabling
Drivers for devices
Overheating
Port Status Indicators
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Solid Green: The link is connected, but there is no traffic
Flickering Green: The link is operating normally (with traffic). The blink rate indicates the link speed
No light: The link is not working, or the port is shut down
Blinking Amber: A fault has been detected (duplex mismatch, excessive collisions, or redundancy check errors, for instance)
Solid Amber: The port is blocked by the spanning tree algorithm, which works to prevent loops within a switched network
Switch Show Commands
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Show Commands: Set of commands in a switch OS to report configuration or interface information
- show config: displays the switch’s configuration
- show starup / show running-config: some undocumented change to the switch, using these commands and comparing the output may reveal the source of a problem
- show interface: lists the state of all interfaces or the specified interface
Interface is not up/up:
- down/down: There is no link
- admin down/down: The interface has been disabled using the shutdowncommand use shutdowncommand to bring it up
- down/error disabled: The interface is disabled due to some error state, spanning tree or port security issue
- up/down suspended: The port is part of a link aggregation group, and the channel has not been negotiated (show etherchannel = show cause of error)
Interface Error Counters
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Interface Error Counters:
- Interface counters record the number of events over time = allows you to diagnose issues with an interface that is up but that is unreliable or performing poorly
Link State: Measures whether an interface is working (up) or not (down), track the uptime or downtime percentage so that you can assess a link’s reliability over time
Resets: The number of times an interface has restarted over the counter period
Discards/drops: An interface may discard incoming and/or outgoing frames for several reasons, including checksum errors, mismatched MTUs, packets that are too small (runts) or too large (giants), high load, or permissions
Interface Error Counters
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Cyclic Redundancy Check Errors
- is calculated by an interface when it sends a frame, derive a 32-bit value, added to the header as the frame check sequence = derives a different value, frame is rejected
Runt Frame Errors
- Malformed Ethernet frame that is smaller than the permitted 64 byte minimum size, caused by a collision, driver issue on the transmitting host
Giant Frame Errors
- Ethernet frame that is larger than the receiving interface will accept 1518 bytes
Jumbo frames: host might be configured to use jumbo frames, but the switch interface is not configured to receive them
Ethernet trunks: A trunk link carries traffic between switches or between a switch and a router
MAC Address Table
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
- A switch learns MAC addresses by reading the source address when a frame is received on a port
- The address mapping for that port is cached in a MAC address table
- The address table is implemented as content addressable memory (CAM), a special type of memory optimized for searching, rather than random access
Network Loop and Broadcast Storm Issues
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Network Loop: is where flooded frames circulate the network perpetually
Broadcast Storm Issues: cause network utilization to go to near maximum capacity and the CPU utilization of the switches to jump to 80% or more
- Verify compatible versions of Spanning Tree Protocol or Rapid Spanning Tree Protocol are enabled on all switches
- Verify the physical configuration of segments that use legacy equipment, such as Ethernet hubs
- Investigate networking devices in the user environment and verify that they are not connected as part of a loop, unmanaged desktop switches and VoIP
Power Over Ethernet Issues
Mod 3.4 Switch Troubleshooting
Objective 5.2 | 5.3 | 5.5
Cabling Issues: Cat 5e or better
Power Budget: When configuring Power over Ethernet, the maximum amount of power available across all switchports.
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Net + Mod 1 Networking Overview22
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Net + Mod 2 Supporting Cabling & Physical Installations18
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Net + Mod 3 Configuring Interface & Switches23
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Net + Mod 4 Configuring Network Addressing31
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Net + Mod 5 Configuring Routing and Advanced Switching36
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Net + Mod 6 Implementing Network Services20
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Net + Mod 7 Explaining Application Services28
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Net + Mod 8 Supporting Network Management20
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Net + Mod 9 Explaining Network Security Concepts17
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Net + Mod 10 Applying Network Security Features15
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Net + Mod 11 Supporting Network Security Design0
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Net + Mod 12 Configuring Wireless Networks0
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Net + Mod 13 Comparing Remote Access Methods0
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Net + Mod 14 Summarizing Cloud Concepts0
