Tài liệu Laboratory Exercises— Solutions docx

The exercises IGMP Concepts and PIM Dense Mode and PIM Sparse Mode Concepts include answers to Review Questions.. The exercise Simple IP Multicast Deployment includes answers to Review Q

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Laboratory Exercises— Solutions

Overview

This module contains solutions to the exercises that are part of the Basic IPMulticast course

There is no solution part to the exercise Applications and IP Multicast since all

the necessary information is provided in the exercise itself

The exercise Initial Lab Setup includes initial router configurations.

The exercises IGMP Concepts and PIM Dense Mode and PIM Sparse Mode Concepts include answers to Review Questions.

The exercise Simple IP Multicast Deployment includes answers to Review

Questions and a sample router configuration

This module includes the following sections:

■ B: Inital Lab Setup

■ B-1: Verification of the Initial Router Configuration

■ C-1: IGMP Concepts and Working

■ C-2: PIM Dense Mode Protocol Basics

■ C-3: PIM Dense Mode Protocol Mechanics

■ D-1: PIM Sparse Mode Protocol Basics

■ D-2: PIM Sparse Mode Protocol Mechanics

■ E-1: PIM Sparse-dense Mode and Manual RP Configuration

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B: Initial Lab Setup

Lab Solution

The initial configurations of routers acting as sources and receivers are provided

as well as configurations of workgroup routers

Note Minor variations in configurations may appear with respect to the platforms used.

The hostnames are referred to in their abbreviated form without the workgroup number.

Source

version 12.0 service timestamps debug datetime service timestamps log datetime

no service password-encryption

! hostname Source

! enable secret 5 $1$I9Vf$lbWnExLuOAxLq1Y8Ckm0E/

enable password cisco

line vty 0 4 password cisco logging synchronous login

! end

R1

! hostname R1

! enable secret 5 $1$d6qE$5QHDfRbqbmPFjAnhd8SwN1 enable password cisco

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ip address 192.168.100.11 255.255.255.255

! interface Serial0/0

no ip address encapsulation frame-relay

no ip mroute-cache

! interface Serial0/0.1 point-to-point description R1-R5

bandwidth 64

ip address 172.16.6.1 255.255.255.0 frame-relay interface-dlci 591

bandwidth 64

! router ospf 1

no log-adjacency-changes network 172.16.0.0 0.0.255.255 area 16 network 192.168.100.11 0.0.0.0 area 16

!

ip classless

! line con 0 exec-timeout 0 0 logging synchronous transport input none line aux 0

! end

R2

! hostname R2

! enable secret 5 $1$eR0m$.Df45QXDydOrc3croKiWv.

ip address 192.168.100.12 255.255.255.255

! interface Loopback1

ip address 172.16.2.2 255.255.255.0

!

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interface Serial0/0

no ip mroute-cache

bandwidth 64

ip address 172.16.1.2 255.255.255.0

ip igmp version 2 frame-relay interface-dlci 291

! router ospf 1

!

ip classless

! end

R3

! hostname R3

! enable secret 5 $1$QQEE$l9YQFlWpSFjZ9uLmulHXX0 enable password cisco

ip address 192.168.100.13 255.255.255.255

! interface Ethernet0/0

ip address 172.16.9.1 255.255.255.0

no ip mroute-cache

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bandwidth 64

! router ospf 1 log-adjacency-changes network 172.16.0.0 0.0.255.255 area 16 network 192.168.100.13 0.0.0.0 area 16

!

ip classless

! end

R4

! hostname R4

! enable secret 5 $1$aRlA$hyJTDYvNPkXeUFohxP32M0 enable password cisco

ip address 192.168.100.14 255.255.255.255

! interface Loopback1

ip address 172.16.5.2 255.255.255.0

! interface FastEthernet0/0

ip address 172.16.5.1 255.255.255.0

no ip mroute-cache half-duplex speed 10

no ip mroute-cache

bandwidth 64

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! router ospf 1

!

ip classless

! end

R5

! hostname R5

! enable secret 5 $1$m8J1$e5JCJIS9Ck0EtW625YLa60 enable password cisco

ip address 192.168.100.15 255.255.255.255

ip address 172.16.7.1 255.255.255.0

no ip mroute-cache

bandwidth 64

! router ospf 1

!

ip classless

line vty 0 4

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password cisco logging synchronous login

! end

R6

! hostname R6

! enable secret 5 $1$m8rn$cTnVe6g5i1a2xQRJEsQBd.

ip address 192.168.100.16 255.255.255.255

ip address 172.16.7.2 255.255.255.0

no ip mroute-cache

ip address 172.16.8.1 255.255.255.0

no ip mroute-cache

bandwidth 64

! router ospf 1

!

ip classless

!

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end

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B-1: Verification of the Initial Router Configuration

Task 1: Verification of the Initial Router Configuration

The tables with IP addresses of the individual interfaces on the workgroup routersare provided below x is the workgroup number and y is 15 + x

Router Interface Address Subnet Mask

Step 1: Loopback IP address assignment

Step 2: LAN IP address assignment

Step 3: WAN IP address assignment

Step 4: Source IP address assignment

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C-1: IGMP Concepts and Working

Answers to Review Questions (after Step 4)

■ What is the IP address of the IGMP Querier on each of your routers' LAN's?

The IGMP Querier is elected as the router, which has the lowest IPaddress on that segment

■ Explain the IGMP Querier election process and the function of the IGMPQuerier in an IGMP context

On a shared segment all routers initially send out an IGMP QueryMessage The router with the lowest IP address on that segment iselected to be the Querier

Note There is no formal IGMP Query Router election in IGMPv1.

The IGMP Querier is responsible for sending periodic IGMP Queries on

a shared segment on which it was elected as an IGMP Querier

■ What is the purpose of the Designated Router listed in show ip igmp interface command?

The Designated router (DR) has no meaning in the PIM Dense mode.The only exception is if IGMP v1 is used simultaneously In this casethe DR also acts as an IGMP Querier since there is no formal

mechanism for election in IGMP v1

The role of the Designated Router in the PIM Sparse mode is essential.The DR is responsible for sending Joins towards the Rendezvous-Point(RP), and for switching-over to the SPT If the DR is on the sourcesegment the DR is also responsible for sending Registers towards theRP

■ Explain the procedure that follows the reception of an IGMP Leave message

on the segment

After an IGMPv2 Querying router receives an IGMP Leave message for

a specific group and if there are no IGMPv1 hosts on that segment, therouter responds with IGMP Group Specific Query for that group Therouter prunes off the traffic for this group if the Group Specific Query isnot responded within the interval

If there are IGMPv1 hosts on the segment, the router simply waits forthe group to time out.,

■ What could be a reason that you see 224.2.127.254 and 239.255.255.255groups as groups joined by the router itself?

The router joins to groups 224.2.127.254 and 239.255.255.255 if it is

configured to listen to sdr announcements with ip sdr listen command.

224.2.127.254 is a classic multicast IP address and 239.255.255.255 is ascoped multicast IP address used by the sdr application

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C-2: PIM Dense Mode Protocol Basics

Task 1: Monitor the network with active multicast source and no

receivers

Answers to Review Questions

■ Complete the following table:

– What is the incoming interface for the (S, G) entry (172.y.8.2, 224.1.2.3) on each router?

– What are the flags for this entry?

– What interfaces are in the outgoing interface list (OIL) for this entry

on each router and what are their statuses?

Router Incoming interface Flags OIL interfaces / Statuses

■ Why are all the interfaces in the OIL pruned? Do they continuously remain inthe pruned state? Explain

All interfaces in the OIL are pruned because there are no receivers.The prune state expires every 3 minutes and the traffic is reflooded

■ Explain the meaning of the flags

The P flag indicates that the (S, G) traffic was pruned off and the T flagindicates that a Shortest Path Tree is used for multicast traffic

Task 2: Monitor the network with active multicast source and receiversAnswers to Review Questions (after Step 3)

■ Complete the following table:

– What is the incoming interface for the (S, G) entry (172.y.8.2, 224.1.2.3) on each router?

– What is an RPF neighbor address?

– What are the flags for this entry?

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– What interfaces are in the outgoing interface list (OIL) for this entry

on each router and what are their statuses?

Router Incoming

interface

RPF neighbor address

Flags OIL interfaces / Statuses

■ Compare your answers to the answers from Step 2 What differences do younotice?

When receivers became active, The C flag appears on last hop routers,which are R2 and R4 and since the group is local L flag appears too.The routers on a SPT towards the source (R1, R5 and R6) remove the Pflag since they are forwarding the traffic R3 still has the P flag since R3does not have a directly connected receiver and is not on a SPT fromany other receiver towards the source

■ What is the meaning of the RPF neighbor: (0.0.0.0) on router R6?

R6 has no RPF neighbor since R6 is the first hop router with a directlyconnected source so the RPF entry shows 0.0.0.0

■ Why is the RPF check failing?

R3 sees no directly connected receivers for the multicast group224.1.2.3 so R3 sends Prune messages towards R6, the upstream RPFneighbor R6 ignores the Prune messages since the 224.1.2.3 staticgroup on Serial 1/0.2 interface is manually configured R4 is alsoconfigured to forward the same multicast traffic for group 224.1.2.3 on ashared Ethernet segment between routers R3 and R4 This traffic arrives

on an interface that is on an OIL list on router R3 and thus causes RPFcheck failures

■ How many packets arrive on the wrong interface?

One half of all received packets from the source are received on a RPF interface and cause RPF Check failures

non-■ What are the implications of RPF failures in a production network?

Some RPF failures are normal when periodic flooding happens If thereare many failures then probably the network is misconfigured

■ How would you fix this problem?

A removal of the static groups usually solves the problem Ensuring thatthere are no loops in the network will prevent RPF Check failures

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C-3: PIM Dense Mode Protocol Mechanics

Task 1: PIM Dense Mode Pruning and Grafting

■ How long did it take for the routers to react with PIM messages after thetopology changed? Why they reacted?

Since PIM relies on the underlying unicast routing protocol (OSPF inthis case) it takes time to converge PIM scans the unicast routing tablefor changes every 5 seconds so we have to wait no more than 5-6seconds

The routers react because of the topology change (the shut down ofsome interfaces) in the network

■ Why did you see (on some links, in Step 2) the Prunes flowing in bothdirections?

Originally the multicast traffic for group 224.1.2.3 was forwarded viaSPT to R2 by R1 When the link between routers R2 and R3 isreenabled and the topology changes, the SPT for multicast group224.1.2.3 for the router R2 is now forwarded via R3 R2 sends the Prunemessage to R1 since the traffic that R1 was forwarding is not arriving onthe RPF interface any longer R2 puts the interface towards R1 into theOIL and starts forwarding the multicast traffic to R1 Therefore R1 had

to prune off that traffic since that traffic is not coming down the SPT

■ What happens after the Prune timer on an interface expires?

When the Prune timer on an interface expires, the interface status ischanged to Forwarding and the traffic is forwarded

Task 3: PIM Assert

■ What event triggers the Assert procedure in PIM?

Receiving a multicast packet on a multi-access interface that is in theOIL triggers the Assert procedure

■ Who is the winner in a normal situation?

In a normal situation the router with a better metric to the source is thewinner

■ If the winner cannot be found, what is the tie breaker?

The higher IP address on a router for that segment is used as atiebreaker

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■ If the source is active, the Assert in PIM Dense mode happens every threeminutes Why?

The Assert in the PIM Dense mode occurs every three minutes because

in that time the prune state expires, the interface goes into a forwardingstate and the multicast packet triggers the Assert procedure again

Tiêu đề	Laboratory Exercises— Solutions
Chuyên ngành	IP Multicast
Thể loại	Laboratory Exercises Solutions
Năm xuất bản	2000

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