anycast rps using msdp for ers 8600 technical

> Anycast RPs Using MSDP for ERS 8600 Technical Configuration Guide

Avaya Data Solutions Document Date: July 30, 2010 Document Number: NN48500-581 Document Version: 1.1

Ethernet Routing Switch

8600

Engineering

Avaya Inc. – Proprietary & Confidential.

Use pursuant to the terms of your signed agreement or Avaya policy. 1

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Abstract

This document covers in detail the application of Anycast RP using Multicast Source Discovery Protocol (MSDP) on the ERS 8600. This feature allows a network operator to establish multiple, redundant RPs in a given PIM-SM domain. A step by step configuration of a sample topology is provided followed by a walk-through of the operation.

This TCG applies to the ERS 8600 software release 5.1

Revision Control

No Date Version Revised by Remarks

1 06/22/2009 1.0 CSE Initial version of Anycast RP application document

1.1 7/29/2010 1.1 CSE Minor edits to correct content



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Table of Contents

Document Updates ........................................................................................................................ 3

Conventions ................................................................................................................................... 3

1. Introduction to Anycast RP on ERS 8600 ........................................................................... 4

1.1 High Level Configuration and Operation ......................................................................... 4 1.2 Benefits of Anycast RPs .................................................................................................. 5 1.3 MSDP and Split Multi-Link Trunking (SMLT) ................................................................... 5

2. Network Topology ................................................................................................................. 6

3. Configuration ......................................................................................................................... 7

3.1 VLAN and Loopback Interface Configuration .................................................................. 7 3.2 OSPF and PIM-SM Global Configuration ........................................................................ 9 3.3 MSDP Configuration ........................................................................................................ 9

4. Operation .............................................................................................................................. 11

4.1 SA Propagation .............................................................................................................. 11 4.2 Delivering the Multicast Stream ..................................................................................... 13 4.3 Failing 8600-2 ................................................................................................................ 15

5. Reference Documentation .................................................................................................. 16



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Document Updates

Conventions

This section describes the text, image, and command conventions used in this document.

Symbols:

Tip – Highlights a configuration or technical tip.

Note – Highlights important information to the reader.

Warning – Highlights important information about an action that may result in equipment damage, configuration or data loss.

Text:

Bold text indicates emphasis.

Italic text in a Courier New font indicates text the user must enter or select in a menu item, button or command:

ERS5520-48T# show running-config

Output examples from Avaya devices are displayed in a Lucinda Console font:

ERS5520-48T# show running-config

! Embedded ASCII Configuration Generator Script

! Model = Ethernet Routing Switch 5520-24T-PWR

! Software version = v5.0.0.011

enable

configure terminal



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1. Introduction to Anycast RP on ERS 8600

The Multicast Source Discovery Protocol (MSDP) is used for two networking applications. First, it enables the advertisement of multicast source information between different Protocol Independent Multicast Sparse Mode (PIM-SM) domains [1]. MSDP is also used within an Autonomous System (AS) to synchronize PIM information between two or more Anycast Rendezvous Points (RPs) to provide RP redundancy [2]. This TCG focuses on the latter application.

Within a given PIM-SM domain, the PIM-SM protocol allows for only a single active RP per multicast group. MSDP allows multiple RPs, called Anycast RPs, to provide service for a given multicast group. The Anycast RP routers establish MSDP adjacencies between each other in order to synchronize information about active multicast sources.

1.1 High Level Configuration and Operation

Each Anycast RP router is configured with the same loopback, i.e. circuitless, IP address which is advertised throughout the network via an IGP such as OSPF. As a result, sources and receivers use the closest RP when sending PIM protocol messages.

Each Anycast RP router is also enabled with MSDP and configured with one or more adjacent MSDP peers. The peers establish a session using TCP port 639 using either a unique loopback or interface IP address. When one of the MSDP enabled routers in the PIM domain learns of a new multicast source it transmits a MSDP Source-Active (SA) message to all of its peers. The receiving MSDP router performs a Reverse Path Forward (RPF) check. The RPF check ensures that the SA is received from the MSDP peer that is ―closest‖ to the originating RP in order to prevent SA loops [1]. Note that this RPF check is different than the multicast routing RPF check. The end result is that all Anycast RPs in the PIM-SM learn about the multicast source.

If there are more than two MSDP enabled routers that are directly connected then a Mesh Group can be configured to reduce SA flooding. The Mesh Group is similar to the IBGP route reflector concept. If a MSDP enabled router receives an SA from a Mesh Group member router it does not re-advertise the SA to other Mesh Group members. The receiving router; however, advertises the SA to other MSDP peers that are not members of the Mesh Group, for example to an MSDP peer in another PIM-SM domain. Note that full mesh connectivity between more than two MSDP peers and Mesh Groups are not required, for example there can be multiple linear MSDP peers within the PIM-SM domain.



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1.2 Benefits of Anycast RPs

Anycast RPs provide a lot of flexibility when designing a multicast network. Having multiple RPs for a given multicast group means that traffic for shared multicast trees does not have to be concentrated onto specific routers or areas of the network. Multicast sources and receivers can communicate with local RPs rather than relying on an RP that may be further away. This results in more optimal forwarding of multicast traffic.

Anycast RPs also allow for more control of mapping multicast groups to RPs. This allows a network administrator to more effectively load-balance the PIM-SM processing amongst a set of RPs.

In addition, Anycast RPs provide a fast-failover solution. In the event that a given RP is no longer available another Anycast RP can immediately resume providing shared tree service for all of its groups. Thus, new multicast receivers are able to join the shared tree and multicast sources would register to the same RP to establish or maintain connectivity.

1.3 MSDP and Split Multi-Link Trunking (SMLT)

In an ERS 8600 Routed SMLT (RSMLT) configuration, an RP with the same IP address can be configured as a loopback interface on both ERS 8600 cluster switches. Due to the way multicast control protocols, such as IGMP and PIM-SM, are forwarded across the Inter-Switch Trunk (IST), both ERS 8600 cluster switches learn about multicast sources and receivers. As a result, if one of the RPs (i.e. ERS 8600) fails, then the RP running on the peer ERS 8600 continues to provide RP services for all multicast groups. Thus, in SMLT topologies where the ERS 8600 switches are the RPs, there is no need to run MSDP between 8600 peers as a redundant, fast-failover solution already exists.

Anycast RPs with MSDP is likely to be used in the following scenarios:

The Anycast RPs and other non-RP MSDP routers are directly connected and in a non-SMLT configuration. If there are more than two MSDP routers then a Mesh Group should be configured to reduce SA flooding.

The Anycast RPs are not directly connected but learn about multicast sources via a MSDP peering session. For example, a local RP may be backed up by an RP that is located on a different campus or geographical region.



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2. Network Topology

The demonstration network depicted below consisted of six ERS 8600s running release 5.1 software. All of the ERS 8600s were in the same Autonomous System. The multicast source is connected to core router 8600-5. The multicast receivers are connected to 8600-1 and 8600-3 representing end users at two separate locations that request the same stream.

Three of the ERS 8600s in the network (8600-2, 8600-4, and 8600-6) are configured as Anycast RPs and enabled with MSDP. The Loopback2 address for each of these RPs is 10.10.10.10/32. This represents the Anycast RP IP address which is injected into OSPF. The PIM-SM Designated Router on the multicast receiver VLANs, (i.e. 8600-1 and 8600-3) will contact the RP that is ―closest‖ from an OSPF perspective when requesting a new stream. The Anycast RP that is closest to 8600-1 is 8600-2 since the link between 8600-1 and 8600-4 has a higher OSPF metric. The Anycast RP closest to 8600-3 is 8600-4.

Similarly, the PIM-SM Designated router on the multicast source VLAN will send PIM Register packets to the ―closest‖ Anycast RP. When the Anycast RP first learns the multicast source, it will transmit an SA message to its two MSDP peers. In this network, 8600-6 does not play a major role as it is configured as an Anycast RP in order to demonstrate MSDP Mesh Groups. One can assume that it provides RP services for another part of the network that is not shown. Note that MSDP is not enabled on 8600-1, 8600-3, and 8600-5.

8600-1

2/1

2/1

8600-2

loopback1=2.2.2.2/32

loopback2=10.10.10.10/32

4/1

Multicast Source

10.5.5.101

Group 239.1.1.10

Multicast Receiver

10.1.1.63

Joins 239.1.1.10

V12

10.12.12.x

V34

10.34.34.x

V103

10.3.3.x

V105

10.5.5.x

2/2 4/52/2

4/30

MSDP peering

RP PIM-SM Rendezvous Point

2/2 2/24/12

Multicast Receiver

10.3.3.64

Joins 239.1.1.10

RP4/29

2/3

2/3

V101

10.1.1.x

8600-3

8600-5

4/29

4/30

V1410.14.14.x

8600-4


loopback2=10.10.10.10/32

RPRP

8600-6


loopback2=10.10.10.10/32

V26

10.26.26.x

V46

10.46.46.x4/29

4/30

V25

10.25.25.x

V4510.45.45.x

V2410.24.24.x

A single OSPF area 0.0.0.0 is used and OSPF is enabled on all ERS 8600 interfaces. PIM-SM is enabled on all ERS 8600 interfaces except for the loopback1 interfaces. The Multicast Source, 10.5.5.101, transmits a stream for multicast group 239.1.1.10.



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3. Configuration

The configuration shown below is for ERS 8600 switch named 8600-2. Similar configuration is performed on the other ERS 8600 switches in the network.

The configuration is performed using CLI. The equivalent configuration can be performed using Passport CLI as well as using Java Device Manager (JDM). See ERS 8600 product documentation for more details [3].

First, layer 2 and layer 3 VLAN configurations will be performed including enabling OSPF and PIM on the appropriate interfaces. Then OSPF and PIM global parameters will be configured. Finally, MSDP will be configured on the three ERS 8600 switches designated as Anycast RPs.

3.1 VLAN and Loopback Interface Configuration

To begin, enter CLI configuration mode by typing ―config term‖. First, set the name of the 8600:

prompt 8600-2

Create the port based VLANs which are all mapped to Spanning Tree Group ―1‖ and assign the appropriate ports. Then disable spanning-tree on the ports as there are no loops and all VLANs are routed. Finally, enable the ports if they are not already enabled.

vlan create 12 type port 1




vlan members add 12 2/2




interface gigabitEthernet 2/1,2/2,4/29,4/30

no spanning-tree stp 1 enable

no shutdown

exit

For each of the VLANs, add an IP address, enable OSPF, and enable PIM.

interface vlan 12

ip address 10.12.12.2 255.255.255.0

ip ospf enable

ip pim enable

exit

interface vlan 24

ip address 10.24.24.2 255.255.255.0

ip ospf enable



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ip pim enable

exit

interface vlan 26

ip address 10.26.26.2 255.255.255.0

ip ospf enable

ip pim enable

exit

interface vlan 25

ip address 10.25.25.2 255.255.255.0

ip ospf enable

ip pim enable

exit

Configure the two loopback interfaces. The first loopback interface is a unique IP address which will be used as the OSPF router-id and for MSDP peering. The second loopback interface is the Anycast RP address. OSPF is enabled on both loopback interfaces while PIM is only enabled on the RP. Note that the second loopback interface only needs to be configured on 8600-2, 8600-4, and 8600-6 in this network.

interface loopback 1

ip address 2.2.2.2/32

ip ospf

exit

interface loopback 2

ip address 10.10.10.10/32

ip ospf

ip pim

exit



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3.2 OSPF and PIM-SM Global Configuration

Set the OSPF Router-Id to the unique IP address corresponding to loopback interface 1. Then globally enable OSPF.

router ospf

router-id 2.2.2.2

exit

router ospf enable

In this network, a static RP is defined on each of the routers. The multicast range 239.1.1.0/24 is mapped to the Anycast RP address. Then PIM-SM is enabled globally.

ip pim static-rp

ip pim static-rp 239.1.1.0/24 10.10.10.10

ip pim enable

3.3 MSDP Configuration

8600-2 has two MSDP peers: 8600-4 and 8600-6. The peering is established between the loopback 1 interfaces of the peer routers.

When configuring the peer, the ―connect-source‖ parameter must be specified to instruct the ERS 8600 to use the loopback 1 IP address as the Source IP address in its MSDP transmissions. Once the MSDP peer is defined it must be enabled.

ip msdp peer 4.4.4.4 connect-source 2.2.2.2

ip msdp peer 4.4.4.4 enable

ip msdp peer 6.6.6.6 connect-source 2.2.2.2

ip msdp peer 6.6.6.6 enable

In this network there are three Anycast RPs that are configured as members of a Mesh Group. On each ERS 8600, the Mesh Group name (i.e. ―group1‖) and members are configured.

ip msdp mesh-group group1 4.4.4.4

ip msdp mesh-group group1 6.6.6.6



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The last step is to set the MSDP originator-id to the loopback 1 address. If this is not done then the originator-id is set (by default) to the RP address when transmitting the SA in which case the receiving ERS 8600 switches will discard the SA due to IP address conflict. Finally, enable MSDP globally.

ip msdp originator-id 2.2.2.2

ip msdp enable



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4. Operation

The state of the MSDP peers is first verified with the following ―show‖ command. Note that the State of the MSDP peers should be ―Established‖.

8600-2:5# show ip msdp summary . . . MSDP Peer Status Summary Peer Address AS State Uptime/ Established SA Downtime Count Count 4.4.4.4 n/a Established 00:05:08 124 0 6.6.6.6 n/a Established 00:05:28 133 0

4.1 SA Propagation

The multicast source is started and transmitted packets to 239.1.1.10. 8600-5 sent a PIM Register packet to the RP address 10.10.10.10. In this case the ―closest‖ RP happened to be 8600-2. This was confirmed by examining the IP Forwarding table on 8600-5 which showed that network 10.10.10.10/32 was reachable via VLAN 25 with next-hop of 8600-2:

8600-5:5# show ip route -s 10.10.10.10/32

================================================================================ IP Route - GlobalRouter ================================================================================ NH INTER DST MASK NEXT VRF COST FACE PROT AGE TYPE PRF -------------------------------------------------------------------------------- 10.10.10.10 255.255.255.255 10.25.25.2 Glob~ 20 25 OSPF 0 IB 20

The PIM mroute table on 8600-2 contained an entry corresponding to this (S,G). Note that the ―A‖ Flag is set for the (S,G) indicating that the information was advertised to the MSDP process.

8600-2:5# show ip pim mroute

================================================================================ PIM Multicast Route - GlobalRouter ================================================================================ Src: 10.5.5.101 Grp: 239.1.1.10 RP: 10.10.10.10 Upstream: 10.25.25.5 Flags: CACHE SG A Incoming Port: Vlan25-4/29, Outgoing Ports: Joined Ports: Pruned Ports: . . . ------------------------------------------------------------------------------- Total Num of Entries Displayed 1/1 Flags Legend: SPT = Shortest path tree, WC=(*,Grp) entry, RP=Rendezvous Point tree, CACHE=Kernel Cache, ASSERTED=Asserted, SG=(Src,Grp) entry, PMBR=(*,*,RP) entry, FWD_TO_RP=Forwarding to RP, FWD_TO_DR=Forwarding to DR, SG_NODATA=SG Due to Join, A=SG Advertised to MSDP, M=SG Created by MSDP, CP_TO_CPU=Copy to CPU, STATIC_MROUTE=Static Mroute, MRTF_SMLT_PEER_SG=Peer SG On Non-DR For SMLT



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As a result the 8600-2 switch stored the entry in its SA Local Cache:

8600-2:5# show ip msdp sa-cache local

MSDP Source-Active Local Cache - 1 entries (10.5.5.101, 239.1.1.10), RP 10.10.10.10

The SA is then advertised by 8600-2 to its two MSDP peers. When 8600-4 and 8600-6 receives the SA, they will store it in their SA Foreign Cache:

8600-4:5# show ip msdp sa-cache

MSDP Source-Active Foreign Cache - 1 entries (10.5.5.101, 239.1.1.10), RP 2.2.2.2, BGP/AS n/a, 00:18:17/00:06:12

Note that the RP was set to 2.2.2.2 as a result of the ―ip msdp originator-id‖ command entered on 8600-2. If this is not set, then the RP would be set to 10.10.10.10 and as a result 8600-4 and 8600-6 would have discarded the SA information due to an IP address conflict with their local loopback 2 addresses.

Also, note the two time stamps at the end of the entry. The first time stamp increments and represents the amount of time the entry has been in the cache. The second time stamp decrements and represents the time remaining before the cache entry ages out. When 8600-4 and 8600-6 receive a periodic SA update (every 60 seconds) this value resets to 6 minutes and 30 seconds (i.e. 390 seconds).

8600-1 8600-2

Multicast Source

10.5.5.101

Group 239.1.1.10

Multicast Receiver

10.1.1.63

Joins 239.1.1.10

V12

10.12.12.x

V34

10.34.34.x

V103

10.3.3.x

V105

10.5.5.x

Multicast Receiver

10.3.3.64

Joins 239.1.1.10

RPV101

10.1.1.x

8600-3

8600-5

V1410.14.14.x

8600-4

RPRP

8600-6

V26

10.26.26.x

V46

10.46.46.x

V25

10.25.25.x

V4510.45.45.x

V2410.24.24.x

MSDP SA Update

ERS 8600-2, 8600-4, and 8600-6 are members of a Mesh Group. As a result, upon receiving the SA, 8600-4 and 8600-6 do not advertise the SA to one another.

Interestingly, although the SA was advertised to 8600-4 and 8600-6 via MSDP, from a PIM perspective, the PIM mroute table was empty since no PIM Joins had been received yet.



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8600-4:5# show ip pim mroute

================================================================================ PIM Multicast Route - GlobalRouter ================================================================================ Total Num of Entries Displayed 0/0

4.2 Delivering the Multicast Stream

Next, the multicast receiver connected to 8600-1 transmitted a request, via IGMP, to receive the 239.1.1.10 multicast stream. This triggered 8600-1 to add an (*,G) entry to its PIM mroute table and send a PIM Join message to the RP 10.10.10.10. Based on the IP Forwarding table on 8600-1, the PIM Join is transmitted to the Anycast RP on 8600-2:

8600-1:6# show ip route -s 10.10.10.10/32 ================================================================================ IP Route - GlobalRouter ================================================================================ NH INTER DST MASK NEXT VRF COST FACE PROT AGE TYPE PRF -------------------------------------------------------------------------------- 10.10.10.10 255.255.255.255 10.12.12.2 Glob~ 20 12 OSPF 0 IB 20

ERS 8600-2 updated its PIM mroute table to add port 2/2 to the outgoing ports list for multicast group 239.1.1.10. Then 8600-2 sends a PIM Join towards the PIM designated router on the multicast source’s subnet to 8600-5 which also updates its PIM mroute table. As a result, the multicast stream is delivered to the multicast receiver connected to 8600-1 via the shared path tree.

Once 8600-1 received the first packet of the multicast stream, it will add an (S,G) entry to its PIM mroute table and transmit a PIM Join to 8600-5 in order to join the shortest path tree. ERS 8600-1 will then Pruned its logical connection to the shared path tree. In this case the logical shared path tree and shortest path tree are the same physical path.

For the multicast receiver connected to 8600-3, a similar sequence of events transpired and the multicast stream is delivered as expected. However, one difference is that the initial PIM Join is transmitted to the Anycast RP on 8600-4 based on the IP Forwarding table on 8600-3:

8600-3:5# show ip route -s 10.10.10.10/32 ================================================================================ IP Route - GlobalRouter ================================================================================ NH INTER DST MASK NEXT VRF COST FACE PROT AGE TYPE PRF -------------------------------------------------------------------------------- 10.10.10.10 255.255.255.255 10.34.34.4 Glob~ 20 34 OSPF 0 IB 20



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The resulting flow of the multicast stream is shown in the diagram below:

8600-1 8600-2

Multicast Source

10.5.5.101

Group 239.1.1.10

Multicast Receiver

10.1.1.63

Joins 239.1.1.10

V12

10.12.12.x

V34

10.34.34.x

V103

10.3.3.x

V105

10.5.5.x

Multicast Receiver

10.3.3.64

Joins 239.1.1.10

RPV101

10.1.1.x

8600-3

8600-5

V1410.14.14.x

8600-4

RPRP

8600-6

V2610.26.26.x

V46

10.46.46.x

V2510.25.25.x

V4510.45.45.x

V2410.24.24.x

The resulting traffic flow shown above is reflected in the PIM mroute table on 8600-5 which showed that the multicast stream is received on local ―Incoming Port‖ 4/5 and delivered to ―Outgoing Ports‖ 4/29 and 4/30 towards the two multicast receivers: 8600-5:5# show ip pim mroute ================================================================================ PIM Multicast Route - GlobalRouter ================================================================================ Src: 10.5.5.101 Grp: 239.1.1.10 RP: 10.10.10.10 Upstream: NULL Flags: CACHE SG Incoming Port: Vlan105-4/5, Outgoing Ports: Vlan25-4/29, Vlan45-4/30, Joined Ports: Vlan25-4/29, Vlan45-4/30, Pruned Ports: Leaf Ports:



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4.3 Failing 8600-2

To demonstrate Anycast RP redundancy, 8600-2 is powered off to simulate a router failure. After approximately 4 seconds, the multicast streams to both multicast receivers resumed.

8600-1 8600-2

Multicast Source

10.5.5.101

Group 239.1.1.10

Multicast Receiver

10.1.1.63

Joins 239.1.1.10

V12

10.12.12.x

V34

10.34.34.x

V103

10.3.3.x

V105

10.5.5.x

Multicast Receiver

10.3.3.64

Joins 239.1.1.10

RPV101

10.1.1.x

8600-3

8600-5

V1410.14.14.x

8600-4

RPRP

8600-6

V2610.26.26.x

V46

10.46.46.x

V2510.25.25.x

V4510.45.45.x

V2410.24.24.x

4/30

2/2

2/3

The PIM mroute table on 8600-4 reflects the new delivery path for the multicast stream. The stream is delivered from 8600-5 to ―Incoming Port‖ 4/30 on 8600-4 and delivered via ―Outgoing Ports‖ 2/2 (to 8600-1) and 2/3 (to 8600-3) towards the two multicast receivers:

8600-4:5# show ip pim mroute source 10.5.5.101 ================================================================================ PIM Multicast Route - GlobalRouter ================================================================================ Src: 10.5.5.101 Grp: 239.1.1.10 RP: 10.10.10.10 Upstream: 10.45.45.5 Flags: SPT CACHE SG A Incoming Port: Vlan45-4/30, Outgoing Ports: Vlan34-2/2, Vlan14-2/3, Joined Ports: Vlan34-2/2, Vlan14-2/3, Pruned Ports: Leaf Ports: . . .

In addition, the ―A‖ Flag was set for the (S,G) entry because now 8600-4 is the Anycast RP closest to the multicast source.



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5. Reference Documentation

Reference # Document Title Publication Number

1 RFC 3618 – Multicast Source Discovery Protocol (MSDP)

2 RFC 3446 - Anycast Rendezvous Point (RP) mechanism using Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP)

3 Avaya Ethernet Routing Switch 8600 - Configuration — Multicast Source Discovery Protocol, Release: 5.1

NN46205-524

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