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Archive for the ‘Multicast’ Category

Basic Multicast part 6 – Anycast RP

December 1, 2012 2 comments

Continuing with Multicast topics I will talk this time about Anycast RP. Anycast RP is used for RP redundancy. As I explained in my previous posts on multicast it is possible to have RP redundancy with Auto-RP by defining multiple RP servicing the same multicast groups (the RP with the highest IP will be selected as the active RP for a specific group by the MA). PIM BSR can also be used for RP redundancy and the process is the same as with Auto-RP apart from the fact that the BSR router doesn´t elect which RP is active for a specific group. In both cases the failover delay is based on the RP/BSR/MA advertisement intervals which are not fast by default (up to 60 seconds). So the whole point with Anycast RP is that the failover is based on the IGP running in the multicast domain which can be really fast (especially when using Bidirectional Forwarding Detection).

 For this post I will use the same topology as the other multicast posts:

AnycastRP

Scenario: R4 and R2 will be configured as static RPs sharing the same IP address. An MSDP session will be established between R4 and R2 in order to synchronize source IP information

 Source: 150.1.0.4

 RPs: R4 and R2 with IP 24.24.24.24

 IGP: EIGRP AS 100

 Platform/IOS: Cisco 2691/12.4(15)T11 Adv IP services

 All the routers in the PIM SM topology are configured with PIM SM. For this post I will only use static RP assignment as it is the most commonly used method for group-to-RP mapping due to its deterministic nature. Auto-RP or PIM BSR could also have been used.

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Basic Multicast part 5 – PIM SSM and SSM mapping

November 28, 2012 3 comments

Continuing with Multicast topic I will talk this time about PIM SSM (Source Specific Multicast RFC 3569) and SSM mapping. In my previous posts on Multicast I demonstrated how to configure PIM DM/SM which uses IGMPv2 for host to router signaling. PIM DM and SM are known as “Any Source Multicast” or ASM. The receivers are willing to receive multicast from any source which is why a RP is needed in order to allow the receivers to discover new sources. With PIM SSM the concept is different as the receivers signal which source they want receive multicast traffic from by using IGMPv3 which means that RPs are not needed and the multicast routers in the multicast domain will only build shortest-path trees (SPT).

 For this post I will use the same topology as the other multicast posts:

Scenario: The Multicast source will send two streams, one for the multicast group 239.10.10.10 and one for the multicast group 239.20.20.20. The first group (239.10.10.10) will be running PIM SM and R4 will be the RP for this group. The second multicast group (239.20.20.20) will be running PIM SSM. The receiver will act as an IGMPv2/v3 receiver. In the second part of this post I will demonstrate how to configure SSM mapping where the receiver will not be IGMPv3 capable.

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Basic Multicast part 4 – PIM Sparse Mode – BSR and Multicast Security

September 11, 2012 4 comments

Continuing with Multicast topic I will talk this time about PIM BSR (Bootstrap Router) which is an alternative way to advertise dynamic RP information. We saw in the previous posts on Multicast that the RP information could be configured statically or dynamically with Auto-RP. Auto-RP is a legacy mechanism which is neither part of the PIMv2 standard nor used in IPv6 Multicast. The issue with Auto-RP is that it uses specific multicast groups to propagate the RP information which gives some challenge in NBMA partially meshed networks and some methods are needed in order to allow the Multicast Auto-RP control plane traffic to be propagate everywhere.

BSR (Bootstrap Router) which is part of PIMv2 standard and used in IPv6 Multicast is similar to Auto-RP but the RP information is not disseminate using Multicast group but instead this information is encapsulated in PIM packets.

 I will also talk about some Multicast security features that can be used in order to protect the Multicast domain.

 Before reading further I invite you to read my previous post on Multicast PIM Sparse Mode if you are not familiar with PIM SM.

 I will use the same network topology as I did in my previous posts on Multicast. Let´s consider the following topology:

Source: The multicast source 150.1.0.4 will be sending to multicast group 239.10.10.10 which is part of the administratively scoped addresses assigned by IANA which is for use in private multicast domains, much like the IP unicast range defined in RFC 1918.

RP: The RP is R4 with IP: 4.4.4.4

BSR: The Bootstrap router is R3 with IP 3.3.3.3

IGP: The IGP used is EIGRP

Platform/IOS: Cisco 2691/12.4(15)T11 Adv IP services

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Basic Multicast part 3 – PIM Sparse Mode – Auto-RP

August 9, 2012 3 comments

Continuing with Multicast topic I will this time talk about PIM SM and Auto-RP. This post is the next part of the previous post called: “Basic Multicast part 2 – PIM Sparse Mode – Static RP” where I talked about how to configure PIM in Sparse Mode but I also explained and demonstrate the source registration process with the RP as well as SPT switchover.

 The topology I am going to use in this post will be the same as the one I used in the previous multicast post.

 Let´s consider the following topology:

Source: The multicast source 150.1.0.4 will be sending to multicast group 239.10.10.10 which is part of the administratively scoped addresses assigned by IANA which is for use in private multicast domains, much like the IP unicast range defined in RFC 1918.

 RP: The RP is R4 with IP: 4.4.4.4

MA: the mapping agent is R3 with IP 3.3.3.3

IGP: The IGP used is EIGRP

Platform/IOS: Cisco 2691/12.4(15)T11 Adv IP services

 We saw in the previous multicast post on PIM SM with static RP that all multicast enabled router need to know the IP address of the RP in order to build the shared tree and signal the RP of the presence of eventual multicast receivers for a specific multicast group.

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Basic Multicast part 2 – PIM Sparse Mode – Static RP

August 5, 2012 4 comments

This is the second part of my previous topic about Multicast. This time I will demonstrate how PIM Sparse Mode works based on the same topology as the previous post.

Let´s consider the following topology:

Source: The multicast source 150.1.0.4 will be sending to multicast group 239.10.10.10 which is part of the administratively scoped addresses assigned by IANA which is for use in private multicast domains, much like the IP unicast range defined in RFC 1918.

 RP: The RP is R4 with IP: 4.4.4.4

 IGP: The IGP used is EIGRP

 Platform/IOS: Cisco 2691/12.4(15)T11 Adv IP services

 As PIM Sparse Mode is a much wider topic than PIM Dense Mode I will start to talk about PIM Sparse Mode with static RP, than Auto-RP, Auto-RP listener and finally PIM BSR.

PIM Sparse Mode is based on the “pull model” or “explicit join” which use a combination of both a shared tree and a source-based tree. The RP is making the connection between the shared-tree (tree build down the Multicast receivers) and the source-based tree (tree built up to the source).

PIM Sparse Mode uses (*,G) entries to forward Multicast traffic unlike PIM Dense Mode. So the key difference between PIM Sparse Mode and PIM Dense Mode is that PIM Sparse Mode the forwarding state in the router is set up as a result of an explicit “join” where in PIM DM (PIM Dense Mode) the forwarding state is set up upon arrival of multicast traffic.

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Basic Multicast part 1 – PIM Dense Mode

March 16, 2012 14 comments

I would like to share some basic Multicast examples. As this topic is quite wide I will make different posts. This first post will talk about PIM Dense Mode. The next post will cover topics such as PIM Sparse Mode, Auto-RP and PIM BSR.

 Let´s consider the following topology:

Source: The multicast source 150.1.0.4 will be sending to multicast group 239.10.10.10 which is part of the administratively scoped addresses assigned by IANA which is for use in private multicast domains, much like the IP unicast range defined in RFC 1918.

IGP: The IGP used is EIGRP

Platform/IOS: Cisco 2691/12.4(15)T11 Adv IP services

 Let ´s start with Dense Mode. PIM Dense Mode is based on the “push” or “implicit join” model where Multicast traffic is flooded throughout the entire multicast domain without the receivers needing to join the specific multicast group being flooded. So PIM Dense Mode is not really scalable and is only suitable for small multicast implementations. The reason of that is the flooding and the (S,G) state creation for every source/group.

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