Answers to Chapter 6 Troubleshooting Exercises

1 What is the output of Example 6 63 telling you? Example 6 63 The Output for Troubleshooting Exercise 1

Turban#debug ip mpacket

IP multicast packets debugging is on R1#

Turban#debug ip mpacket

IP multicast packets debugging is on R1#

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

IP:

s

192

168

14

35

(Serial0/1

307)

d

228

13

20

216

len

573

mrouting

disabled

Answer: Multicast packets are being dropped because multicast routing is not enabled on the router.

2 What is the output of Example 6 64 telling you? Example 6 64 The Output for Troubleshooting Exercise 2

R2#

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

IP:

s

192

168

13

5

(Ethernet©)

d

227

134

14

26

len

583

not

RPF

interface

Answer: Packets for group 227 134 14 26 sourced by 192 168 13 5 are being received on interface EO This interface is apparently not the upstream interface toward the source however. Therefore it is not the RPF interface and the packets are failing the RPF check and are being dropped

3 What is the output of Example 6 65 telling you?

Example 6 65 The Output for Troubleshooting Exercise 3

R3#debug ip mpacket

IP multicast packets debugging

is on

R3#

IP: s 172 16 3 5© (Serial© 405)

d 224

©

1 4© (Serial© 407)

len 52 mforward

IP: s 172 16 3 50 (Ethernet©) d

224 ©

1

40 len 62 not RPF

interface

IP: s 172 16 3 5© (Ethernet©) d

224 ©

1

39 len 62 not RPF

interface

IP: s 172 16 3 5© (Serial© 405)

d 224

©

1 39 (Serial© 407)

len 52 mforward

Answer: A router at address 172 16 3 50 is both a C RP (224 0 1 39) and a mapping agent (224 0 140) The Auto RP messages are being received on interface SO 405 and are being forwarded out interface SO 407 The messages also are being received on interface EO and are failing the RPF check Therefore interface SO 405 is the upstream interface to 172 16 3 50

4 In Figure 6 12 which of the four routers is the PIM designated router?

Figure 6 12 The Topology for Troubleshooting Exercises 4 5 and 6

172 16 12 18 172 16 12 18 172 16 12 18

To S

172 16 12 18

172 16 30 18/24 172 16 30 10/24 172 16 30 75/24

172 16 30 147/24

Answer: The PIM DR is the router with the highest IP address Therefore RT4 is the PIM DR

5 In Figure 6 12 which router is sending IGMPv2 queries to the group member?

Answer: The IGMPv2 querier is the router with the lowest IP address Therefore RT2 is the querier.

6 Table 6 5 shows the unicast routes to source 172 161218 m Figure 6 12 Which router is the PIM forwarder?

Table 6 5 Unicast Routes to 172 1612 18 in Figure 6 12

Router

Next Hop

Protocol

Metric

R1

172 16 50 5

OSPF

35

R2

172 16 51 80

EIGRP

307200

R3

172 16 13 200

EIGRP

2297856

R4

172 16 44 1

OSPF

83

Answer: The PIM forwarder is the router with the lowest administrative distance Given equal administrative distances the forwarder is the router with the lowest metric The administrative distance of EIGRP is 90 and the distance of OSPF is 110 so EIGRP is lower. Between the two EIGRP routes R2 s route has a lower metric so R2 is the PIM forwarder.

7 Example 6 66 shows an RPF trace taken from the PIM domain in Figure 6 10 which is running RIP 2 as its unicast IGP Does this trace indicate a possible problem?

Example 6 66 The mtrace for Troubleshooting Exercise 7

Sombrero#mtrace 192 168 14 35 192 168 10 8 235 1 2 3

Type escape sequence to abort

Mtrace from 192 168 14

35 to 192 168 10 8 via group 235 1 2 3

From source (?) to destination (?)

Querying full reverse

path

0 192 168 10 8

1 192 168 10 1 PIM

[192 168 14 0/24]

2 192 168 200 2 PIM

[192 168 14 0/24]

3 192 168 201 2 PIM

[192 168 14 0/24]

4 192 168 204 1 PIM

[192 168 14 0/24]

5 192 168 14 35

Sombrero#

Answer: Yes There are equal cost paths between Beret and Boater via either T\irban or Fez Beret can have only one RPF neighbor, so it picks the neighbor with the highest IP address In this case Turban has the highest IP address but the trace shows that the path through Fez is used Therefore there is an apparent problem between Beret and Ttirban

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