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50 Cards in this Set
- Front
- Back
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How does frame relay reduce network costs?
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Using less equipement, less complexity, and easier implementation.
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True/False? Frame Relay provides greater bandwidth, reliability and resiliency than private and leased lines.
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True
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True/False? With Frame, distance between nodes is contributing high cost.
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False, distance does not matter.
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T/F? Customers can define their own Virtual circuits in increments as small as 4kb/s and with dedicated lines, only increments of 64 kb/s are provided.
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True.
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What is DLCI?
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Data link connection identifier. # identifying the link.
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T/F? A FrameRelay WAN is a mesh of swiches interconnected by trunk links.
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True
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Frame Relay replaces what protocol?
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x.25 protocol; additional error and flow control but high overhead, used mainly for credit card auth and teller machines.
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How does frame relay recognizes errors?
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through a standard CRC(Cyclic Redundancy Check)
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What makes frame relay faster than x.25?
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lower overhead, no error correction, simply drops packets w/o notification when errors are detected
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How does frame relay recognizes errors?
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through a standard CRC(Cyclic Redundancy Check)
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What is a VC?
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Virtual circuit. Logical connection between two DTEs through a frame relay network. No direct electrical connection from end to end.
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What is SVC and PVC and what modes do they operate in?
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Switched virtual circuits and Permanent Virtual circuit.
SVCs - CALL SETUP, DATA TRANSFER, IDLE, CALL TERMINATION PVCs - DATA TRANSFER AND IDLE |
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How are VCs identified?
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By DLCI which is assigned by the service provider
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T/F? DLCI has global significance?
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False, they have only local significance, two devices can use different DLCI to refer to the same connection
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T/F? Users pay for the bandwidth not the circuit.
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True
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DLCIs # are 0 to __ and ___ to 1023 are reservered for special purposes, therefore most DLCIs are 16 to ____.
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0 to 15 and 1008 to 1023
16 to 1023 |
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The _____ is stored in the address field of every frame transmitted.
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DLCI
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What are the congestion control bits in the frame relay frames?
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FECN, BECN, DE
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What is FECN?
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Foward Explicit Congestion Notification. Bit set by FR network to inform DTE receiving frame that congestion was experienced in path from source to dest. DTE can then request that higher level protocols take flow-control actions
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What is BECN?
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Backward Explicit Congestion Notification. Bit set by FR network traveling in the opposite direction of frames encountering a congested path. DTE can then request that higher level protocols take flow-control actions
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What is the DE bit in congestion control?
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Disgard eligible
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Explain how FR detects error messags?
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The FCS is calculated prior to transmission by the sending node, and the result is inserted in the FCS field. At the distant end, a second FCS value is calculated and compared to the FCS in the frame. If the results are the same, the frame is processed. If there is a difference, the frame is discarded.
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What is the theoretical # limit for VCs per link?
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1000, this is why huge network cannot afford to go full mesh but partial mesh; pattern of mesh is based on data flow requirements
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FR supports all network protocols such as?
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IP, IPX and appleTalk
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What does frame relay use to do address mapping?
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Inverse ARP to obtain layer 3 addresses to layer 2 addresses. Router uses response from remote device to populate an address to DLCI mapping tables.
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T/F? Inverse ARP is enabled by default in cisco routers.
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True
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What is the command to show the frame relay settings on the router?
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show frame-relay map
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show frame-relay map
serial 0/0/0(up): ip 10.1.1.2 dlci 102(0x66, 0x1860), static, Broadcast, CISCO, status defined, active What is th ip 10.1.1.2 represent? |
The destination address
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show frame-relay map
serial 0/0/0(up): ip 10.1.1.2 dlci 102(0x66, 0x1860), static, Broadcast, CISCO, status defined, active In this output, what is the (0x66 and 0x1860)? |
Hexadecimal value and the value as it would appear o nthe wire
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In frame relay, what is the command to map a static address? Give an example.
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Frame-relay map protocol 10.1.1.2 102 broadcast cisco/ietf
use ietf when connecting to non-cisco router |
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What is LMI?
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Local Management Interface - keep alive mechanism that provides status info between DTE and DCE every 10 secs
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What is the command to show LMI info?
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show frame-relay lmi
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Name the LMI extension.
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VC status messages- provides info about PVC integrity, new, exsisting an deletion of PVC
Multicasting Global addressing- Give connection identifier global significance Simple Flow control- intended for devices who can't use the congestion notification bits and needs some level of flow control |
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What are the LMI types?
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Cisco
ANSI Q933a Are incompatible with each other, type configured on router must match the type used on the service provider |
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How many LMI/VC identifiers are there and write out the range?
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1024
0-1023(cisco) |
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T/F? The switch and its connected router do not care about the LMI types but do care about the encapsulations and the DTE(end point routers) do not care about the encapsulation.
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False. The connected switch and router care about using the same LMI but the end point DTEs only care about the encapsulation.
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Frame-relay map ip 10.1.1.2. 102 broadcast
What is the signifant of the broadcast syntax? |
Used for Non-broadcast Multiple Access networks such as Frame Relay, X.25 and ATM
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What are subinterfaces used for?
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To resolve the split horizon issues with Frame Relay because it is a NBMA network and mostly uses a hub and spoke topology? Router must send data out the same way it came in one because it only has one phhysical circuit with multiple VCs.
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T/F? With a P2P subinterface, each subinterface has it's own IP and subnet?
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True
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T/F? With P2Multipoint subinterface, all interfaces on VCs use different subnets.
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False, All interfaces or VCs use the same subnet
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What is CIR?
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Committed Information Rate- amt of data that the network receives from access circuits
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What is CBIR?
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Committed Burst Information Rate (CBIR) - a negotiated rate above the CIR which customers can use to transmit for a short burst
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What is BE size?
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Excess Burst (BE) size - bandwidth available above the CBIR up to the access rate of link
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What is Forward Explicit Congestion Notification(FECN)?
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-Indirect notification sent to routers in times of congestion
-set on every frame that upstream switches receives |
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What is Backward Explicit Congestion Notification(BECN)
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-Direct notifications sent to routers in times of congestion
-Set on every frame that downstream switch receives |
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Explain Discard Eligibility(DE) bit.
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DTE devices can set this value to 1 on certain unimportant frames so that these frames can be dropped first during congestions
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During congestion what rules apply as for incoming frames not exceeding the CIR, exceeding the CIR, and exceeding the CIR plus the BE
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-incoming frame does not exceed the CIR, pass through
-incoming frame exceeds the CIR, marked with DE -incoming frame exceeds the CIR plus the BE, it is discarded |
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What commands can be used to troubleshoot frame relay?
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-show interface[interface]
exp. show interface serial 0/0/0.102 -show frame-relay lmi -show frame-relay pvc |
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what does the frame-relay pvc command used to view?
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-displays status of all PVCs configured
-use to verify PVC and traffic status -user to view # of BECN and FECN packets received |
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What is the command to clear dynamic created frame relay maps created from using Inverse ARP?
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Clear frame-relay-inarp
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