CCNA VOIP Ch 6
Card Set Information
CCNA VOIP Ch 6
What type of interface type would you connect an analog fax machine to?
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
: 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
dial-peer voice 99 pots
user dials 1159, what digits does rtr send out port 1/0/0?
digit stripping rule for pots.
What is the default codec used by a VOIP dial peer?
Which patterns could match any dialed number up to 32 digits in length? choose 2.
a and c
After you create a translation rule, how is it applied?
To a translation profile.
Which of the following digit manipulation cmds will work for a VOIP dial peer?
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.
What is the final method used by a router to match an inbound dial peer for incoming calls?
dial peer 0
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
you can't control distance between routers.
(this multiple choice question has been scrambled)
FXS connects to what?
end devices. analog phone, modem, fax machine
How do you find what ports are FXS? (cli cmd)
show voice port summary
What types of signaling can FXS use?
loop start (default)
FXO connects to what?
any trunk type
Detail cas T1 1-24 setup
ds0-group 1 timeslots 1-24 type fxo-loop-start
verify: show voice port summary
Detail CCS T1 1-24 setup
pri-group timeslots 1-24
router assumes ISDN pri for signaling.
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.
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.
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.
Detail CME CLI for the following.
phone 1 x1101 fxs 0/0/0
phone 2 x1102 fxs 0/0/1
call each other.
dial-peer voice 1101 pots
dial-peer voice 1102 pots
verify: sh dial-peer voice summ
: debug voip dialpeer
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.
negate with no digit strip
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
dial-peer voice 2000 voip
session target ipv4:10.1.1.2
note: codecs must match on both ends.
default codec for voip dial peers is g729
Describe . wildcard
matches 0-9 and * ex. 20.. matches 2000 thru 2099
Describe + wildcard
matches one or more instance of preceding digit
ex. 5+23 matches 5523 55523 555523 etc.
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
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)
inserts a 1 second pause between dialed digits
describe the following:
7 digit dialing area
10 digit dialing area
11 digit long-distance dialing
Detail PLAR cli syntax
voice port 0/0/0
dn num 1102
connection plar 1102
as soon as user lifts handset, ext 1102 is dialed.
Private Line Automatic Ringdown
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.
Detail how to setup calls to go to receptionist using PLAR.
connection plar 1500
connection plar 1500
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.
What cmd tests the dial plan against a specific number?
sh dialplan number **num**
rtr lists more specific match first.
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
5. Dial peer 0
What should you avoid dial peer 0?
any voice codec
no DTMF relay
IP Prec 0 (no QOS)
no RSVP (QOS)
no application support (no IVR)
no DID support
Detail prefix digits
: prefix digits POTS dial peer,
adds digits to the front of a number
detail forward-digits number
: POTS dial peer,
specifies number of digits to forward, (right justified)
detail no digit strip -- digit strip
mode: POTS dial peer, enables/disables digit strip.
POTS strips any explicitly defined digits.
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
detail voice translation-profile
: 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.
how do you setup dynamic WAN to PSTN failover
Use Preference commands.
preference 0 is primary path.
preerence 1 is secondary path.
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.
Define the 3 enemies of VOIP traffic.
Lack of bandwidth
Jitter (delay variation)
Define network requirement for Voice and Video
A. Packet loss
B. End to End delay
B. 150 ms or less
b. 30 ms or less
c. 1% or less
(this multiple choice question has been scrambled)
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.
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.
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.
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.
What methods of QOS can you apply to traffic INPUT?
What methods of QOS can you apply to traffic OUTPUT?
Fragmentation and Interleaving
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.