07-17-2019 01:09 PM
I'm trying to get this Multicast scenario to work for a troubleshooting I'm working on but for some reason it is not working as expected, maybe you guys can help me out. I have Pim Dense Mode and IGMP enable on both R1 and S1. I'm using iperf 2.x to send multicast traffic. Multicast Client (MC) is the iperf server subscribing to Multicast Group (MG) 239.2.3.4:
[root@MC ~]# iperf -s -u -B 239.2.3.4 -i 1 ------------------------------------------------------------ Server listening on UDP port 5001 Binding to local address 239.2.3.4 Joining multicast group 239.2.3.4 Receiving 1470 byte datagrams UDP buffer size: 208 KByte (default) ------------------------------------------------------------
When I do that, S1 receives an IGMP Membership Report and creates a IGMP Group on S1 and an entry on PIM mroute table:
S1#sh ip igmp groups IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter Group Accounted 239.1.1.2 Vlan1 05:08:38 00:04:52 10.0.0.1 239.2.3.4 Vlan1 00:02:03 00:04:51 10.0.0.40 224.0.1.40 Vlan1 23:02:51 00:04:52 10.0.0.1 S1# S1#sh ip mroute IP Multicast Routing Table Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected, L - Local, P - Pruned, R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet, X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group, G - Received BGP C-Mroute, g - Sent BGP C-Mroute, N - Received BGP Shared-Tree Prune, n - BGP C-Mroute suppressed, Q - Received BGP S-A Route, q - Sent BGP S-A Route, V - RD & Vector, v - Vector, p - PIM Joins on route, x - VxLAN group Outgoing interface flags: H - Hardware switched, A - Assert winner, p - PIM Join Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 239.1.1.2), 05:09:14/00:04:16, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Vlan1, Forward/Dense, 05:09:14/stopped GigabitEthernet1/0/6, Forward/Dense, 05:09:14/stopped (*, 239.2.3.4), 00:02:39/00:04:15, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Vlan1, Forward/Dense, 00:02:39/stopped GigabitEthernet1/0/6, Forward/Dense, 00:02:39/stopped (*, 224.0.1.40), 1d00h/00:04:16, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: GigabitEthernet1/0/6, Forward/Dense, 05:10:30/stopped Vlan1, Forward/Dense, 23:03:27/stopped S1#
But that entry does not get propagated to R1:
R1#sh ip mroute IP Multicast Routing Table Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected, L - Local, P - Pruned, R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet, X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group, G - Received BGP C-Mroute, g - Sent BGP C-Mroute, N - Received BGP Shared-Tree Prune, n - BGP C-Mroute suppressed, Q - Received BGP S-A Route, q - Sent BGP S-A Route, V - RD & Vector, v - Vector, p - PIM Joins on route, x - VxLAN group Outgoing interface flags: H - Hardware switched, A - Assert winner, p - PIM Join Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 239.255.255.250), 05:11:40/00:04:53, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Ethernet0/1, Forward/Dense, 05:11:39/stopped Ethernet0/0, Forward/Dense, 05:11:40/stopped (*, 224.0.1.40), 05:11:48/00:04:59, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Ethernet0/1, Forward/Dense, 05:11:39/stopped Ethernet0/0, Forward/Dense, 05:11:48/stopped R1#
R1 and S1 have formed a neighbor relationship:
R1#sh ip pim nei PIM Neighbor Table Mode: B - Bidir Capable, DR - Designated Router, N - Default DR Priority, P - Proxy Capable, S - State Refresh Capable, G - GenID Capable, L - DR Load-balancing Capable Neighbor Interface Uptime/Expires Ver DR Address Prio/Mode 172.17.1.1 Ethernet0/1 05:13:44/00:01:41 v2 1 / S P G R1# S1# sh ip pim nei PIM Neighbor Table Mode: B - Bidir Capable, DR - Designated Router, N - Default DR Priority, P - Proxy Capable, S - State Refresh Capable, G - GenID Capable, L - DR Load-balancing Capable Neighbor Interface Uptime/Expires Ver DR Address Prio/Mode 172.17.1.2 GigabitEthernet1/0/6 05:14:10/00:01:41 v2 1 / DR S P G S1#
R1 and S1 configs are attached
Thanks in advance!
07-18-2019 12:35 AM
Hi
I am not an expert in multicast ..
IGMP is the protocol used by multicast receivers to communicate their willingness to listen to a particular multicast group. When a host wants to join a multicast group.
- why IGMP with dense mode? dense mode is going flood traffic anyway.
I think you only need IGMP config on S1 and not on R1 interfaces.
There is bi-dir pim command on S1.
I would remove the bi-dir pim command from S1 .. change to sparse-mode or remove the IGMP commands and test.
I dont think there is any need of IGMP with dense mode.
07-18-2019 05:59 AM
07-18-2019 06:34 AM
I agree with OMZ in that I don't think the IGMP configuration is needed on the routed interfaces on both the router and switch.
07-18-2019 08:57 AM
07-18-2019 09:17 AM
07-24-2019 08:58 AM
if S1 (IGMP Snooping Disabled) does not have active listeners and R1 is sending Multicast Traffic, how long before S1 sends a PRUNE msg to R1? Also, Would in this scenario Multicast Packets been flooded to all ports on S1 until the Prune msg is received by R1? or S1 would drop all Multicast traffic because it has no members for that group?
Thanks in advance
07-24-2019 10:03 AM
07-24-2019 10:09 AM
Hi joseph,
Thanks for your answer. In this case both R1 and S1 have PIM (Dense Mode) and IGMPv2 enabled, only IGMP Snooping has been disabled. R1 and S1 have a PIM Neighbor relantionship formed thus S1 can send prune messages to R1. I'm just wondering if flooding will occur on S1 before it gets pruned or not.
Thanks again
07-24-2019 11:53 AM
07-24-2019 12:19 PM
Hello,
You don't need PIM enabled on the switch (S1) and the router doesn't need IGMP. Enabling PIM on the Router and IGMP snooping on the Switch should work.
07-24-2019 12:53 PM
S1 is in L3 mode so I do believe I need PIM enabled. Also it seems IGMP needs to be enable for PIM to work on Cisco switches.
07-24-2019 02:02 PM
OK. I didn't know that you're doing L3 between your switch and router. Once PIM is enabled, IGMP is also enabled. Just use IGMPv2 and not 3. Typically, enabling PIM would've enabled IGMPv2 by default, except you manually set it to IGMPv3.
07-18-2019 01:05 AM
Hello amartinsbrz,
you are trying to use IGMP version 3 for Source Specific Multicast with PIM dense mode.
I don't think the two are compatible.
Either you move to PIM sparse mode and use an SSM address range that includes the group you are using for tests, or you change IGMP version to IGMP version 2.
Hope to help
Giuseppe
07-18-2019 05:57 AM
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