CCNA VOIP Ch 6

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boultonm
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216249
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CCNA VOIP Ch 6
Updated:
2013-05-10 11:46:14
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VOIP
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Ch 6
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  1. What type of interface type would you connect an analog fax machine to?

    a. FXS
    b. FXO
    c. E&M
    d. BRI
    FXS
  2. Detail CLI syntax for a t1 line using chanels 1-6 connected to the PSTN using FXO loop start signaling.
    • ds0-group 1 timeslots 1-6 type fxo-loop-start
    • (note: ds0-group is for CAS signaling)

    • Note:   for CCS signaling, t1, PSTN use
    • pri-group timeslots 1-6
    • CCS signaling router assumes ISDN PRI signaling.

    t1 lines have 24 timeslots.

    verify with show voice port summary
  3. dial-peer voice 99 pots
    destination-pattern 115.
    port 1/0/0

    user dials 1159,  what digits does rtr send out port 1/0/0?
    9

    digit stripping rule for pots.
  4. What is the default codec used by a VOIP dial peer?
    G.729
  5. Which patterns could match any dialed number up to 32 digits in length?  choose 2.

    a.   .+
    b.   [0-32]
    c.    T
    d.    &
    a and c
  6. After you create a translation rule, how is it applied?
    To a translation profile.
  7. Which of the following digit manipulation cmds will work for a VOIP dial peer?

    a. prefix
    b. forward-digits
    c. translation-profile
    d. digit-strip
    • c.
    •  
    • a b and d are all pots digit manipulation methods

    prefix puts the defined number in front of the number.

    forward-digits tells the ftf how many (right-justified) digits to send   (note: right justified counts from right to left)

    digit-strip is built in and strips any explicitly defined number.  use no digit-strip to negate.
  8. What is the final method used by a router to match an inbound dial peer for incoming calls?
    dial peer 0
  9. Which of the following is not an area you can use QOS to manage?

    A. packet jitter
    B. variable delay
    C. fixed delay
    D. router queuing
    C. 

    you can't control distance between routers.
    (this multiple choice question has been scrambled)
  10. FXS connects to what?
    end devices.  analog phone, modem, fax machine
  11. How do you find what ports are FXS? (cli cmd)
    show voice port summary
  12. What types of signaling can FXS use?
    ground start

    loop start  (default)
  13. FXO connects to what?
    any trunk type

    • PBX system
    • PSTN
    • CO
  14. Detail cas T1  1-24 setup
    ds0-group 1 timeslots 1-24 type fxo-loop-start

    verify:  show voice port summary
  15. Detail CCS T1 1-24 setup
    pri-group timeslots 1-24

    router assumes ISDN pri for signaling.
  16. Detail T1 interfaces channel and timeslot numbering for CCS.
    T1 interface, channel 23 (timeslot 24) is used for signaling.  timeslot 1-24 for North America.

    E1, channel 16 (timeslot 17) is used for signaling.  timeslot 1-30 for EU.
  17. What are the two types of dial peers.  define.
    POTS, anything traditional, FXS, FXO, E&M, digital voice port.

    VOIP,  anything with an IP address.
  18. Define a voice call leg.
    a call leg represents a connection to or from (or both) a voice gateway from a POTS or VOIP source. 

    It's like a routing table for phone numbers.
  19. Detail CME CLI for the following.

    phone 1  x1101  fxs 0/0/0
    phone 2  x1102  fxs 0/0/1

    call each other.
    • config t
    • dial-peer voice 1101 pots
    • destination-pattern 1101
    • port 0/0/0

    • dial-peer voice 1102 pots
    • destination-pattern 1102
    • port 0/0/1

    • verify:  sh dial-peer voice summ
    • debug: debug voip dialpeer
  20. What is the digit strip rule?

    if dial peer is 55..
    user dials 5521
    what digits leave the port?
    POTS,  rtr automatically strips any explicitly defined digit from a POTS dial peer before forwarding the call.

    21

    negate with no digit strip
  21. Detail voip dial peer using CLI 

    extension block 2...
    ip address of outbound port 10.1.1.1
    ip address of other end port 10.1.1.2
    codec g711ulaw
    • config t
    • dial-peer voice 2000 voip
    • destination-pattern 2...
    • session target ipv4:10.1.1.2
    • codec g711ulaw

    note: codecs must match on both ends.

    default codec for voip dial peers is g729
  22. Describe . wildcard
    matches 0-9 and *  ex. 20..  matches 2000 thru 2099
  23. Describe +  wildcard
    • matches one or more instance of preceding digit
    • ex. 5+23  matches 5523  55523  555523 etc.
  24. Describe  []  

    Describe use of ^
    matches range of digits

    ^ means does not match

    • ex. [1-3]22 matches 122 222 322
    • ex. [^1-3]22 matches 022 422 522 622 722 822 922 and *22
    •  
  25. describe T wildcard 
    matches any number of dialed digits  0-32 in length

    problem is that after you dial your string, it is still waiting for the next digit for 10 seconds  (t302 timer)
  26. describe ,
    inserts a 1 second pause between dialed digits
  27. describe the following:

    [2-9]......

    [2-9]..[2-9].......

    1[2-9]..[2-9].......

    [469]11 

    011T  
    7 digit dialing area

    10 digit dialing area

    11 digit long-distance dialing

    service numbers

    international dialing
  28. Detail PLAR cli syntax

    voice port 0/0/0
    dn num 1102
    • conf t
    • voice-port 0/0/0
    • connection plar 1102

    • as soon as user lifts handset, ext 1102 is dialed.
    • Private Line Automatic Ringdown
  29. What is DNIS?   ANI?
    Dialed Number Information Service    number dialed.  (used on digital calls, incoming, not used with PSTN)

    Automatic Number Identification   number sending the call.  (sent on analog calls, incoming.  Not useful to alert rtr where call should go)

    You can setup PLAR to route all inbound calls to the receptionist.
  30. Detail how to setup calls to go to receptionist using PLAR. 

    port 2/0/0
    port 2/0/1
    ext 1500
    • conf t
    • voice-port 2/0/0
    • connection plar 1500
    • exit
    • voice-port 2/0/1
    • connection plar 1500
    • exit
  31. What 2 rules guide call processing and digit manipulation in the CME?
    Most specific destination pattern always wins.

    When a match is found, the rtr immediately processes the call.
  32. What cmd tests the dial plan against a specific number?
    • sh dialplan number **num**
    • rtr lists more specific match first.
  33. Detail, in order the 5 step dial-peer matching process.
    • 1. match DNIS using incoming called-number config
    • 2. match ANI using answer-address config
    • 3. match caller ID info using ANI using destination-pattern config
    • 4. match incoming POTS using port dial-peer config
    • 5. use dial peer 0

    • 1. DC            DNIS   Called-num 
    • 2. AA            ANI     Answer-address
    • 3. AD            ANI     Dest-pattern
    • 4. PP             POTS   Port dial-peer
    • 5. Dial peer 0
  34. What should you avoid dial peer 0?     
    • any voice codec
    • no DTMF relay
    • IP Prec 0 (no QOS)
    • VAD enabled
    • no RSVP  (QOS)
    • Fax-rate voice
    • no application support (no IVR)
    • no DID support
  35. Detail prefix digits
    • Mode: prefix digits   POTS dial peer, 
    • adds digits to the front of a number
  36. detail forward-digits number
    • mode: POTS dial peer,
    • specifies number of digits to forward, (right justified)
  37. detail no digit strip  --  digit strip
    mode:  POTS dial peer,  enables/disables digit strip.

    POTS strips any explicitly defined digits.
  38. detail num-exp match digits set digits
    • mode:  global,   transforms any defined number into another number.
    • ex.  num-exp 4... 5...
    • ex.  num-exp 0 5000
  39. detail voice translation-profile
    • mode: global ----  for both  POTS or VOIP dial peer,  
    • you can configure up to 15 rules, you set it up in global mode, and apply it to either POTS or VOIP dial peer.

    Like an access list.  
  40. how do you setup dynamic WAN to PSTN failover
    Use Preference commands. 

    preference 0 is primary path.

    preerence 1 is secondary path.
  41. Explain basic COR rules  (Class of restriction)
    Rule 1:  If there is no outgonig COR list applied, the call is always routed.

    • Rule 2:  If there is no incoming COR list applied, the call is always router.
    •  
  42. Define the 3 enemies of VOIP traffic.
    Lack of bandwidth

    • Delay: 
    • Fixed delay 
    • Variable delay 
    • Jitter (delay variation)

    Packet loss  
  43. Define network requirement for Voice and Video

    A. Packet loss
    B. End to End delay
    C. Jitter
    B. 150 ms or less

    b. 30 ms or less

    c. 1% or less
    (this multiple choice question has been scrambled)
  44. What are the 3 common QOS models?
    Best effort - default on every network.  First come first serve.

    Integrated Services (IntServ) - uses reservations, not scalable, uses RSVP, (Resource Reservation Protocol)

    Differentiated Services (DiffServ) - you define what network traffic goes into classes, each class gets a piece of the bandwidth.
  45. List 5 QOS mechanisims.
    Classification and Marking - usually ACL based and marked at L2 or L3.

    Congestion Management - All QOS queuing strategies fall into this category. RUles are set up that kick in when congestion occurs.

    Congestion Avoidance - This basically drops enough non essential packets so congestion does not occur in the first place.

    Policing and Shaping - Policing limits a defined type of traffic to a certain bandwidth number and drops the excess. Shaping queues excess traffic and tries to send it later.

    Link Efficiency - Compression



    Note for CCNA Voice, only two categories are covered.  Link Efficiency and queuing algorithms.
  46. Define 3 Link Efficiency mechanisms.
    Payload Compression - compresses application data.

    Header Compression - for small payload packets, but bunches of them.  Header traffic becomes significant. cRTP (compressed real time protocol) can take 40 byte header down to 2-4 bytes.

    Link Fragmentation and Interleaving (LFI) - addresses serialization delays by chopping large packets into smaller ones. 
  47. Define 3 Queuing Algorithms
    Weighted Fair Queuing (WFQ) - (default) - Balances available BW among all senders.

    Class-Based Weighted Fair Queuing (CBWFQ) - Allows you to specify what traffic gets what % of the BW.

    Low Latency Queuing (LLQ) - also referred to as PQ-CBWFQ (Priority Queuing).  same as CBWFQ with PQ added. This lets the HI priority (voice) traffic to not only get guaranteed BW but first BW. 
  48. What methods of QOS can you apply to traffic INPUT?
    • Classification
    • Marking
    • Policing
  49. What methods of QOS can you apply to traffic OUTPUT?
    • Marking
    • Policing
    • Shaping
    • Congestion Management
    • Congestion Avoidance
    • Compression
    • Fragmentation and Interleaving
  50. Define AutoQOS levels
    auto qos voip - RTR or L3sw - no trust, uses NBAR (Network Based Application Recognition) to id traffic.

    auto qos voip trust - rtr or L3sw - device explicitly trusts markings, does not rely on CDP to verify IP phone is at other end.

    auto qos voip cisco-phone - sw - trusts markings from IP phone if verified by CDP.

    • auto qos voip cisco-softphone - sw - trusts markings only if CDP can verify softphone.
    •  

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