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48 Cards in this Set
- Front
- Back
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Application Layer |
Where users actually communicate to computers. It is in play when accessing to the network in need. Act as an interface between actually application programs. Responsible for identifying and establishing the availability of intended communication partner and determine whether the sufficient resources for this partner is exist or not. |
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Presentation Layer |
Present data to the Application layer and responsible for data translation and code formatting. A translator providing coding and conversion functions. Ensure that data transferred from the Application layer of one system can be read by the Application layer of other |
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Session Layer |
Responsible for setting up, managing, and then tearing down sessions between Presentation layer entities. Provide dialog control between devices or nodes. Coordinate communication between systems and serves to organize their communication by offering simplex, half duplex, and full duplex. |
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Transport Layer |
Segment and reassemble data into data stream. Provide end-to-end data transport services and can establish a logical connection between the sending host and destination host on an inter-network. Provide mechanisms for multiplexing upper layer applications, establishing sessions, and tearing down virtual circuits by providing transparent data transfer |
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Network Layer |
Defines end-to-end delivery of packets and defines logicaladdressing to accomplish this. Manage device addressing, tracks the location of devices on the network, and determines best way to move data to transport traffic between devices that are not locally attached. Router is network layer. It also defines how routing works and how routes are learned; andhow to fragment a packet into smaller packets to accommodate media with smaller maximumtransmission unit sizes |
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Data Link Layer |
Provide physical transmission of data and handles error notification, network topology, and flow control. Ensure messages delivered to proper device on a LAN using hardware addresses and translate messages from the network layer into bits for physical layer to transmit. Format message into pieces (data frame) and add customized header containing the hardware destination and source address. Data link has 2 sub-layers: Media Access Control (MAC) 802.3: define how packets are placed on media. When a frame is received, the switch looks at the destination hardware address and finds theinterface if it is in its MAC address table. If the address is unknown, the frame is broadcast on allinterfaces except the one it was received on. Logical Link Control (LLC) 802.2: responsible for identifying network layer protocol and then encapsulating them. LLC header tell Data Link layer what to do with a packet once a frame is received. |
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Physical Layer |
Do 2 things: send and receive bit (0/1). Communicate directly with actual communication media on the same network.. Specify electrical, mechanical, procedural, and functional requirement for activating, maintaining, and deactivating a physical link between end systems. Identify interface between data terminal equipment (DTE) located on service provider, and data communication equipment (DCE) being attached device. Physical addresses or MAC addresses are used to identify devices at layer 2. |
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Router |
By default, not forward any broadcast or multicast packets Use logical address in a network layer header to determine the next hop router to forward the packet to Can use access lists by Administrator, to control security on the types of packets allowed to enter or exit an interface Can provide layer 2 bridging functions if needed and can simultaneously route through the same interface Layer 3 devices provide connections between virtual LANs Can provide QoS for specific types of network traffic |
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Collision Domain |
A part of a network where packet collisions can occur. A collision occurs when two devices send a packet at the same time on the shared network segment. The packets collide and both devices must send the packets again, which reduces network efficiency. Collisions are often in a hub environment, because each port on a hub is in the same collision domain. By contrast, each port on a bridge, a switch or a router is in a separate collision domain.
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Classful Routing vs Classless Routing |
All interface within the classful address space have the same subnet mask . RIP and IGRP Classless routing protocol do support the advertisement of subnet information. VLSM for RIPv2, EIGRP, OSPF. So, different length of subnet masks for different router interface |
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WAN |
The idea behind a WAN is to be able to connect two DTE networks together through a DCE network. The network’s DCE device (includes CSU/DSU) provides clocking to the DTE-connected interface (the router’s serial interface) |
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Router Decrement TTL Value |
Routers decrement the TTL by 1 every time they forward a packet; if a router decrements the TTL to 0, it throws away the packet. This prevents packets from rotating forever.” I want to make it clear that before the router forwards a packet, the TTL is still remain the same. |
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ARP Cache |
When a host needs to reach a device on another subnet, the ARP cache entry will be that of the Ethernet address of the local router (default gateway) for the physical MAC address. The destination IP address will not change, and will be that of the remote host |
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Half and Full Duplex |
Half Duplex: use one wire pair with digital signal running in both direction. Use CSMA/CD protocol to help revent collisions and permit retransmitting if collisions occur. Full Duplex: use 2 pairs of wires at the same time. Use P2P connection between transmitter of transmitting device and receiver of receiving device. No collision occur |
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Microsegmentation |
A network design (functionality) where each workstation or device on anetwork gets its own dedicated segment (collision domain) to the switch. Each network devicegets the full bandwidth of the segment and does not have to share the segment with other devices.Microsegmentation reduces and can even eliminate collisions because each segment is its owncollision domain -> .Note: Microsegmentation decreases the number of collisions but it increases the number ofcollision domains.
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Layer 2 Switch |
Faster than router because dont take time to look at network layer header information but frame's hardware address before deciding to either forward, flood, or drop frame Create private, dedicated collision domains and provide independent bandwidth each port. Provide: hardware based bridging, wire speed, low latency, and low cost. |
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Root Bridge |
To elect the root bridge in the LAN, first check the priority value. The switch having the lowestpriority will win the election process. If Priority Value is the same then it checks the MAC Address;the switch having the lowest MAC Address will become the root bridge. |
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Ethernet |
Ethernet network is a shared environment so all devices have the right to access to the medium. Ifmore than one device transmits simultaneously, the signals collide and can not reach thedestination. If a device detects another device is sending, it will wait for a specified amount of time beforeattempting to transmit.When there is no traffic detected, a device will transmit its message. While this transmission isoccurring, the device continues to listen for traffic or collisions on the LAN. After the message issent, the device returns to its default listening mode. |
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Router on a stick |
Allow to use sub-interfaces to create multiple logical networks on a singlephysical interface. |
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CSU/DSU vs Modem |
CSU/DSU is used to convert digital signals from a router to a network circuit such as a T1, while amodem is used to convert digital signals over a regular POTS line. |
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Rapid-PVST |
Based on IEEE-802.1D Spanning Tree Protocol (STP). Provides Layer 2 load-balancing for the VLAN on which it runs. Each instance of PVST+ on a VLAN has a single rootswitch. This root switch propagates the spanning-tree information associated with that VLAN to allother switches in the network. Because each switch has the same information about the network,this process ensures that the network topology is maintained and optimized per VLAN.But PVST+ has only 3 port states(discarding, learning and forwarding) while STP has 5 port states (blocking, listening, learning,forwarding and disabled). Discarding is a new port state in PVST+. When RSTP has converged there are only 2 port statesleft: discarding & forwarding
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Root bridge |
The path cost to the root bridge is the most important value to determine which portwill become the root port on each non-root switch. In particular, the port with lowest cost to the rootbridge will become root port (on non-root switch). If two bridges have equalpriority then the MAC addresses are compared; |
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Configuring the Native VLAN for Untagged Traffic
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A trunk port configured with 802.1Q tagging can receive both tagged and untagged traffic. Bydefault, the switch forwards untagged traffic in the native VLAN configured for the port. The nativeVLAN is VLAN 1 by default. |
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Spanning Tree Protocol (STP) |
STP (802.1d) is used to prevent Layer 2 loops by shut down any redundant links One big disadvantage of STP is the low convergence which is very important in switched network. |
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Benefits of VLANs |
VLAN is a network structure which allows users to communicate while in different locations bysharing one multicast domain and a single broadcast. 1. The popularity of VLANs that changes, adds, and moves can be attained simplyby making necessary configurations on the VLAN port. Time-consuming, re-addressing, and hostreconfigurations is now a thing of the past, because network configuration can be made at easewhen need arises. 2. A VLAN typically solve the scalability issues that exist in a large network by breaking the maindomain into several VLAN groups or smaller broadcast configurations, thereby encourage bettercontrol of multicast traffic as well as broadcast domains. 3. High-security can be positioned in different VLAN groups to ensure that non-members cannotreceive their broadcasts. On the other hand, a router is added and workgroups relocated into centralized locations. 4. A more efficient use of bandwidth can be achieved allowing many logical networks to use thesame network infrastructure. 5. VLANs are typically used to achieve multiple purposes. They are popularly used to reducebroadcast traffic. Each VLAN creates a separate, smaller broadcast domain.6. Better administrationVLANs facilitate grouping of multiple geographical stations. When VLAN users move to anotherphysical location, the network does not have to be configured. |
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Dynamic Trunking Protocol (DTP)
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A Cisco proprietary protocol for negotiating trunking on a linkbetween two devices and for negotiating the type of trunking encapsulation (802.1Q) to be used. |
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Rapid Spanning Tree Protocol (RSTP) |
An enhancement of the original STP 802.1D protocol.The RSTP 802.1w protocol is an IEEE open implementation. Cisco has its own proprietary implementation of RSTP, that includes the benefits of its Per-VLAN spanning tree protocols, calledRapid-PVST+. 802.1w introduced an evolution of the Significantly reduces theconvergence time after a topology change occurs in the network. While STP can take 30 to 50seconds to transit from a blocking state to a forwarding state, RSTP is typically able to respondless than 10 seconds of a physical link failure.RSTP works by adding an alternative port and a backup port compared to STP. These ports areallowed to immediately enter the forwarding state rather than passively wait for the network toconverge.RSTP bridge port roles:* Root port – A forwarding port that is the closest to the root bridge in terms of path cost*Designated port – A forwarding port for every LAN segment* Alternate port – A best alternatepath to the root bridge. This path is different than using the root port. The alternative port moves tothe forwarding state if there is a failure on the designated port for the segment.* Backup port – Abackup/redundant path to a segment where another bridge port already connects. The backupport applies only when a single switch has two links to the same segment (collision domain). Tohave two links to the same collision domain, the switch must be attached to a hub.* Disabled port– Not strictly part of STP, a network administrator can manually disable a port To activate the Rapid-PVST+ protocol: switch(config)#spanning-tree mode rapid-pvst |
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Encapsulation types of VLANs |
Cisco switches can use two different encapsulation types for trunks, the industry standard 802.1qor the Cisco proprietary ISL. Generally, most network engineers prefer to use 802.1q since it isstandards based and will interoperate with other vendors. |
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VLAN Range |
VLAN 1 is the default VLAN on Cisco switch. It always exists and can not be added, modified orremoved.VLANs 1002-1005 are default VLANs for FDDI & Token Ring and they can’t be deleted or used forEthernet. |
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Unknown destinations on VLAN |
Each VLAN resides in its own broadcast domain, so incoming frames with unknown destinationsare only transmitted to ports that reside in the same VLAN as the incoming frame. |
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Bridge ID |
STP use bridge id to keep track all switches in the network The bridge with lowest bridge ID is root bridge |
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Root Port |
This is the port that is the closest to the root bridge in terms of path cost. The STA elects a single root bridge in the whole bridged network (per-VLAN). The root bridge sends BPDUs that are more useful than the ones any other bridge sends. The root bridge is the only bridge in the network that does not have a root port. All other bridges receive BPDUs on at least one port.
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Designated Port |
A port is designated if it can send the best BPDU on the segment to which it is connected. 802.1D bridges link together different segments, such as Ethernet segments, to create a bridged domain. On a given segment, there can only be one path toward the root bridge. If there are two, there is a bridging loop in the network. All bridges connected to a given segment listen to the BPDUs of each and agree on the bridge that sends the best BPDU as the designated bridge for the segment. The port on that bridge that corresponds is the designated port for that segment. |
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Traceroute
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Used to verify therouter hop path traffic will take but in this case since the hosts are in the same LAN there will beno router hops involved. |
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Router on a stick configuration-InterVLAN |
In order for multiple VLANs to connect to a single physical interface on a Cisco router,subinterfaces must be used, one for each VLAN. This is known as the router on a stickconfiguration. Also, for any trunk to be formed, both ends of the trunk must agree on theencapsulation type, so each one must be configured for 802.1q or ISL. |
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Inter-VLAN routing |
A VLAN is a broadcast domain, so computers on separate VLANs are unable to communicate without the intervention of a routing device. Any device that supports Layer 3 routing, such as a router or a multilayer switch, can be used to perform the necessary routing functionality. Regardless of the device used, the process of forwarding network traffic from one VLAN to another VLAN using routing is known as inter-VLAN routing.
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Multilayer switching on Inter-VLAN |
Multilayer switching is more scalable than any other inter-VLAN routing implementation. This is because routers have a limited number of available ports to connect to networks. Additionally, for interfaces that are configured as a trunk line, limited amounts of traffic can be accommodated on that line at one time.
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Legacy on Inter-VLAN |
Inter-VLAN routing is performed by connecting different physical router interfaces to different physical switch ports. The switch ports connected to the router are placed in access mode and each physical interface is assigned to a different VLAN. Each router interface can then accept traffic from the VLAN associated with the switch interface that it is connected to, and traffic can be routed to the other VLANs connected to the other interfaces.
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802.1Q protocol, or Virtual Bridged |
802.1Q protocol, or Virtual Bridged Local Area Networks protocol, mainly stipulates the realizationof the VLAN. 802.1Q is a standardized relay method that inserts 4 bytes field into the originalEthernet frame and re-calculate the FCS. 802.1Q frame relay supports two types of frame: markedand non-marked. Non-marked frame carries no VLAN identification information.
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Different types of VLAN trunk modes |
Auto, on, and desirable |
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STP convergence (Layer 2 convergence) |
Happens when bridges and switcheshave transitioned to either the forwarding or blocking state. When layer 2 is converged, root bridgeis elected and all port roles (Root, Designated and Non-Designated) in all switches are selected. |
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“Native VLAN mismatch” error
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Appear by CDP if there is a native VLAN mismatch on an802.1Q link. “VLAN mismatch” can cause traffic from one vlan to leak into another vlan. |
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IPv6 the loopback address |
Written as,1This is a 128bit number, with the first 127 bits being '0' and the 128th bit being '1'. It's just a singleaddress, so could also be written as ::1/128. |
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IPv6 |
Allows plug and play option to the network devices byallowing them to configure themselves independently. It is possible to plug a node into an IPv6network without requiring any human intervention. This feature was critical to allow networkconnectivity to an increasing number of mobile devices. This is accomplished byautoconfiguration. IPv6 does not implement traditional IP broadcast, i.e. the transmission of a packet to all hosts onthe attached link using a special broadcast address, and therefore does not define broadcastaddresses. In IPv6, the same result can be achieved by sending a packet to the link-local allnodes multicast group at address ff02::1, which is analogous to IPv4 multicast to address224.0.0.1. |
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Ipv6 unicast-routing |
Enables IPv6 forwarding on a Cisco router If this command is not recognized, your version of IOS does not support IPv6. |
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IPv6 Anycast |
Used for one-to-nearest communication, meaning an Anycast addressis used by a device to send data to one specific recipient (interface) that is the closest out of agroup of recipients (interfaces). |
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Organizationally Unique Identifier (OUI) |
24-bit number that uniquely identifies a vendor,manufacturer, or other organization globally or worldwide.They are used as the first 24 nits of the MAC address to uniquely identify a particular piece ofequipment. |
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Hierarchical addressing network addressing scheme |
Reduces routing table entries Ease of management and troubleshooting |
