Term
| What are the contents of the Frame Relay LAPF header? |
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Definition
DLCI - 10 bits FECN - 1 bit BECN - 1 bit DE - 1 bit
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Term
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Definition
| Data Link Connection Identifier -- 10 bit address. |
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Term
| Are DLCIs local or global? |
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Definition
| DLCIs are locally significant only. |
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Term
| What follows the FR LAPF header? |
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Definition
The encapsulation header.
[image] |
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Term
| What are the two kinds of FR encapsulation headers? |
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Definition
Cisco, IETF
R1(config)#interface serial0/1
R1(config-if)#encapsulation frame-relay [ietf]
R1(config-if)#frame-relay lmi-type [cisco | ansi | q33a] |
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Term
| What field identifies the L3 protocol in the IETF FR encapsulation header? |
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Definition
| Network Layer Protocol ID (NLPID) |
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Term
| What protocol suite provides global addressing in Frame Relay? |
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Definition
LMI (local management interface)
Also provides: inverse ARP, multicasting, virtual circuits. |
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Term
| What are three LMI types? |
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Definition
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Term
| What is the LMI DLCI for Cisco LMI? |
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Definition
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Term
| What is the LMI DLCI for ANSI and ITU LMI? |
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Definition
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Term
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Definition
LMI sends status messages on DLCI 0 (ANSI/ITU) and 1023 (Cisco) for:
global addressing
Multicasting
inverse arp |
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Term
| What DLCIs are allowed in Cisco LMI? |
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Definition
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Term
| How many total DLCIs are available for use in Cisco LMI? |
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Definition
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Term
| How many DLCIs are available when using ANSI and ITU? |
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Definition
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Term
| How many LMIs total are allowed on a single interface? |
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Definition
| Depends on MTU. For MTU = 1500, 296 DLCIs per interface. |
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Term
| How often are LMI messages sent? |
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Definition
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Term
| How does a switch respond to a DTE's LMI Status inquiry message? |
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Definition
| With a Status message that contains the DLCIs on defined VCs. |
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Term
| What does every 6th status message contain? |
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Definition
| A complete status update. |
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Term
| When does a FR router consider the interface dead? |
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Definition
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Term
| How are LMIs enabled/disabled on a FR interface? |
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Definition
| LMIs are enabled/disabled using "keepalive" / "no keepalive" |
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Term
| Is split horizon enabled or disabled by default on FR interfaces? |
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Definition
| Disabled -- multiple VCs might terminate on a single physical interface. |
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Term
| Is split horizon enabled or disabled on FR sub-interfaces? |
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Definition
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Term
| When would you use static DLCI to IP mapping? |
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Definition
| When the far-end does not support inverse ARP or is not directly connected. |
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Term
| On what types of interfaces can static DLCI to IP mappings be configured? |
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Definition
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Term
| Why can't you use static DLCI to IP mapping on point to point interfaces? |
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Definition
| Because only a single DLCI is allowed for point to point interfaces -- all outgoing traffic uses that DLCI. |
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Term
| What triggers FR Inverse ARP? |
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Definition
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Term
| What happens to Inverse ARP if LMI is disabled? |
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Definition
| Inverse ARP won't work without LMI. |
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Term
| How does Inverse ARP work with LMI? |
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Definition
| LMI Status messages advertise DLCIs (L2 addresses). Routers then use Inverse ARP to query for L3 (IP) addresses associated with each DLCI. |
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Term
| Who usually sets the DE bit? |
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Definition
| the sending router (it knows what traffic is important) |
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Term
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Definition
| Typically FR switches but can also be receiving router. |
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Term
| What does a router do when BECN received? |
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Definition
| Shaper slows down by 25% until mincir. |
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Term
| What happens after 16 Tc intervals without a BECN? |
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Definition
| Shaping rate grows by 1/16 during each Tc until max rate is achieved. |
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Term
| What are the default for FR CIR and minCIR? |
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Definition
CIR = 56 K
minCir = .5 * CIR |
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Term
| How does CIR related to Bc and Tc? |
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Definition
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Term
| Name 3 valid serial connectors |
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Definition
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Term
| What is the maximum recommended CPU load if you are going to use compression? |
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Definition
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Term
| What kind of compression uses the most memory? |
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Definition
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Term
| What is the formula for the number of links required for a full-mesh FR network? |
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Definition
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Term
| When can the "if-needed" keyword by used with "ppp authentication chap" |
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Definition
| Only with TACACS or TACACS+. Allows you to skip authentication if the user has already authenticated by going through the ASCII login procedure |
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Term
| Name the four configuration options for FR end-to-end keepalives. |
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Definition
Bidirectional (send and receive)
Request (send only)
Reply (receive only)
Passive-reply (receive side only, no timers) |
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Term
| Is FR end-to-end keepalive part of LMI? |
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Definition
| No, end-to-end keepalive is a Cisco-only enhancement that is sent on the data DLCI. |
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Term
| Which compression algorithm uses more CPU? |
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Definition
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Term
Given the following, what are Bc Be and Tc?
policy-map SHAPE-ALL
class default
shape average 96000 |
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Definition
"Class Based Shaping"
If rate < = 320kbps:
Bc = Be = 8000
Tc = Bc/rate = 83 msec |
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Term
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Definition
FRF.9 defines payload compression for Frame-relay.
Uses LZS compression algorithm. |
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Term
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Definition
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Term
| How is legacy FRF.12 config different from interface FRF.12 config? |
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Definition
Legacy FRF.12:
1) is configured in a FRTS map-class
2) requires FRTS
3) requires a queueing tool on shaped packets.
Interface FRF.12:
1) is configured on the interface
2) creates dual FIFO if no queueing |
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Term
| Does predictor or stacker compression user more memory? |
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Definition
Predictor.
"To predict the future, you must remember the past." |
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Term
| By how much does RTP header compression reduce the size of the header? |
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Definition
| From 40 bytes to 2 or 4 for IP/UDP/RTP header. |
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Term
| How is PPP framing related to HDLC? |
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Definition
| PPP basically uses the same header as HDLC, adding a standardized protocol field and some padding. |
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Term
| What four things does PPP LCP provide? |
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Definition
1) Link Quality Monitoring
2) Looped Link Detection
3) L2 load balancing (MLPPP)
4) Authentication (CHAP,PAP) |
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Term
What is the fragment size for the following:
int multilink 0
bandwidth 256
ppp multilink
ppp multilink group 1
ppp multilink interleave
ppp multilink fragment-delay 10 |
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Definition
Fragment size = BW * fragment-delay
= 256000 bps * .01 sec
= 2560 bits
= 320 bytes |
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Term
You want your router to respond to any BECNs received on the VC by slowing the rate at which it sends traffic. What command configures your router to do this?
A frame-relay adaptive-shaping becn
B frame-relay becn respond
C frame-relay traffic-shape becn
D frame-relay traffic-shape becn fecn |
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Definition
| A frame-relay adaptive-shaping becn |
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Term
| What policy map class configuration mode commands can result in your router sending Q.922 test frames? |
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Definition
shape fecn-adapt
A Frame Relay service provider can mark the Forward Explicit Congestion Notification (FECN) bit in a frame to tell the receiver to generate a Q.922 test frame directed toward the sender. |
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