CCIE R&S Core Knowledge Question(10)

1. R1#show frame pvc interface serial 1/0

PVC Statistics for interface Serial1/0 (Frame Relay DTE)

Active     Inactive      Deleted       Static
Local          1            0            0            0
Switched       0            0            0            0
Unused         0            0            0            0

DLCI = 103, DLCI USAGE = UNUSED, PVC STATUS = ACTIVE, INTERFACE = Serial1/0

input pkts 0             output pkts 0            in bytes 0
out bytes 0              dropped pkts 0           in pkts dropped 0

out pkts dropped 0                out bytes dropped 0
in FECN pkts 0           in BECN pkts 0           out FECN pkts 0
out BECN pkts 0          in DE pkts 0             out DE pkts 0
out bcast pkts 0         out bcast bytes 0
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
pvc create time 04:48:15, last time pvc status changed 04:48:14

R1#show traffic-shape serial 1/0

Interface   Se1/0
Access Target    Byte   Sustain   Excess    Interval  Increment Adapt
VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)   Active
-             128000    960    3840      3840      30        480       BECN

Given the output above, which type of traffic-shaping is configured on interface s1/0?

Highlight for answer: Generic Traffic-Shaping ('traffic-shape' command under interface s1/0). We can tell this because the VC(virtual circuit) field in the 'show traffic-shape serial 1/0′ output is null. This is because GTS does not support per-VC traffic-shaping.

2. R3#sh frame map
Serial0/0 (up): ip 155.3.0.3 dlci 503(0×1F7,0×7C70), static,
broadcast,
CISCO, status defined, active
TCP/IP Header Compression (inherited), connections: 218959117
RTP Header Compression (inherited), connections: 218959117

R5#sh frame map
Serial1/0 (up): ip 155.1.0.5 dlci 305(0×131,0×4C10), static,
broadcast,
CISCO, status defined, active
TCP/IP Header Compression (enabled), connections: 256
RTP Header Compression (enabled), connections: 256

Given the above output, what is the fundamental difference between the TCP and RTP header compression configurations on R3 and R5?

Highlight for answer: On R3, TCP and RTP header compression have been enabled on the interface level as indicated by the ‘inherited' description in the 'show frame-relay map' output.  On R5 it has been enabled via the frame-relay map map statement(with the keyword ‘compress').

3. Which markings are trusted by default on the interface when you configure the following on a Cisco 3560 switch:

SW1(config)#int f0/1
SW1(config-if)#mls qos trust

Highlight for answer: If no keyword is specified when the command is entered, then DSCP markings are trusted by default when the ‘mls qos trust' interface-level command is configured.

4. By default, what is the TTL of an EBGP peering?

Highlight for answer: 1

5. Which protocol enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers?

Highlight for answer: Diffusing update algorithm (DUAL)