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[Junos] Verify if the RP information is configured on the LHR (Last-Hop Router)

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Article ID: KB21588 KB Last Updated: 07 May 2020Version: 4.0
Summary:

This article shows how to verify whether the Rendezvous Point (RP) information is configured on the Last-Hop Router (LHR).

 

Symptoms:

When troubleshooting a multicast issue in KB21586 - Resolution Guide - Troubleshoot Multicast issue with Junos OS device configured as Layer 3 (running PIM protocol), you may need to check if the rendezvous point (RP) is configured for the Multicast group on the LHR (Last-Hop Router).

On the LHR, do you see the RP and the Multicast Group configured?

The following network topology is referenced in the solution:

 

 

Note: Refer to KB21591 - Sample Multicast Network Topology with Junos OS devices for locating the LHR and for definitions of the components.

Solution:

Run the following commands to view information about the RP:

root@LHR> show pim rps
root@LHR> show pim rps extensive 

Below is an example of the expected output for the network topology above:

root@LHR# run show pim rps
Instance: PIM.master
Address family INET
RP address               Type        Holdtime Timeout Groups Group prefixes
192.168.1.1              static             0    None      3 224.0.0.0/4

root@LHR# run show pim rps extensive
Instance: PIM.master
Address family INET

RP: 192.168.1.1    <----
Learned via: static configuration   <----
Time Active: 1w3d 00:49:07
Holdtime: 0
Device Index: 25
Subunit: 32769
Interface: pime.32769
Group Ranges:         224.0.0.0/4    <----
Active groups using RP:
        224.200.200.200
        224.100.100.100    <----

        total 3 groups active
Register State for RP:
Group           Source          FirstHop        RP Address      State    Timeout
224.200.200.200 192.168.100.10  192.168.20.2    192.168.1.1     Suppress      43

In this example, the RP 192.168.1.1 is learned on the LHR via a static configuration for the group-range 224.0.0.0/4.

For an explanation of the fields in these commands "show pim rps" and "show pim rps extensive," refer to show pim rps.

If no RP is listed for the queried group, then the device does not have the RP configured. Configure the RP on the device for this specific Multicast group. For instructions, refer to Configuring Static RP.

If you see the RP but don't see the group, then check the configuration on the RP. Check if the Multicast group is added in the RP configuration. The command is:

set protocols pim rp static address <RP ip address> [group-ranges <group address>]

In the configuration below, notice that the group-range is not specified. If you do not specify the group-range, then the RP configured acts as the RP for all the groups in the range 224.0.0.0/4.

LHR

set vlans CLIENT vlan-id 100 l3-interface irb.100
set interfaces ge-0/0/10 unit 0 family inet address 192.168.10.1/24
set interfaces ge-0/0/20 unit 0 family inet address 192.168.20.1/24
set interfaces irb unit 100 family inet address 192.168.100.1/24
set interfaces ge-0/0/15 unit 0 family ethernet-switching port-mode trunk vlan members all
set protocols igmp interface irb.100
set protocols ospf area 0.0.0.0 interface ge-0/0/10.0
set protocols ospf area 0.0.0.0 interface ge-0/0/20.0
set protocols ospf area 0.0.0.0 interface irb.100
set protocols pim rp static address 192.168.1.1  <----
set protocols pim interface ge-0/0/10.0
set protocols pim interface ge-0/0/20.0
set protocols pim interface irb.100

RP

set interfaces ge-0/0/20 unit 0 family inet address 192.168.20.2/24
set interfaces ge-0/0/15 unit 0 family inet address 192.168.15.1/24
set interfaces lo0 unit 0 family inet address 192.168.1.1/24
set protocols ospf area 0.0.0.0 interface ge-0/0/15.0
set protocols ospf area 0.0.0.0 interface ge-0/0/20.0
set protocols ospf area 0.0.0.0 interface lo0.0
set protocols pim rp local address 192.168.1.1   <----
set protocols pim interface ge-0/0/20.0
set protocols pim interface ge-0/0/15.0‚Äč

Note: If your LHR or RP is an SRX device, then your configuration will also have PIM enabled on the relevant security zones and security policies to allow traffic between the security zones.

Refer to steps 3 & 4 in KB28362 - [SRX] Configuration example - Multicast PIM Sparse Mode for more information. For example, if the LHR is an SRX device, it also needs this configuration:

set security zones security-zone trust address-book address 192.168.100.0 192.168.100.0/24
set security zones security-zone trust host-inbound-traffic protocols pim
set security zones security-zone trust interfaces ge-0/0/15.0
set security zones security-zone untrust address-book address 224.100.100.100 224.100.100.100/32
set security zones security-zone untrust host-inbound-traffic protocols pim
set security zones security-zone untrust interfaces ge-0/0/10.0
set security zones security-zone untrust interfaces ge-0/0/20.0
set security policies from-zone trust to-zone untrust policy p1 match source-address 192.168.100.0
set security policies from-zone trust to-zone untrust policy p1 match destination-address 224.100.100.100
set security policies from-zone trust to-zone untrust policy p1 match application junos-udp-any
set security policies from-zone trust to-zone untrust policy p1 then permit

 

Modification History:

2020-05-07: Updated links and checked article for validity and accuracy; article valid and still relevant

 

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