Re: Multicast configuration confusion

alanraczek11 · ‎05-12-2020

Hi,

I came to managing a network a few months ago, I am NOT a network SME. I am trying to figure out multicast issues. Developer has this setup:

SRV1 (10.16.16.228, using UDP 224.4.205.58-61) streaming video to SRV2 (10.16.16.228). SRV2 is then streaming processed video to UDP 239.0.0.1. User is trying to see the video from a workstation on 10.16.16.18.

So I did some digging and 'show run pim' shows switches are configured for SSM. A 'show ip igmp interface VLANxxx' shows we are using IGMP v2. So from what I have read SSM does not use an RP and also SSM uses an address block of 232.0.0.0/8, and SSM needs IGMPv3. So I am totally confused with our configuration (being as I am told this worked before but I don't know WHEN it worked before). Seems to me the application needs to use different UDP or the network config needs to change to use an RP and addresses in the 239.0.0.x space. Would I be correct?

TIA.

Sergiu.Daniluk · ‎05-12-2020

Hi @alanraczek11

To me it looks like both sources (SRV1 and SRV2 - the IP of SRV2 needs correction) and receivers are in the same subnet - 10.16.16.X/24. But correct me if this is not accurate.

Because of this, you do not need PIM, as you do not route the mcast traffic. On your switches, all you need is an IGMP Querier. (verify who is the querier using show ip igmp snooping querier).

What is the IGMP version running on your srv/receivers? Depending on this, you can adjust the version on your switch as well.

Regards,

Sergiu

alanraczek11 · ‎05-12-2020

Good catch, yes SRV2 should be 10.16.16.44. The switches are using IGMPv2 at the moment. But I thought SSM requires IGMPv3? So, if the Xmit and Rec 'entities' are in same subnet this would not be an issue? From what you are saying I am not routing then it's a moot point.

alanraczek11 · ‎05-12-2020

Should have included this output:

Sergiu.Daniluk · ‎05-12-2020

To run SSM you need indeed IGMPv3. However, since all your mcast traffic is being forwarded only inside the subnet (no routing), then you do not run SSM. You only do L2 multicast switching. And for this, IGMPv2 works like a charm. :-)

Cheers,

Sergiu

alanraczek11 · ‎05-12-2020

Thank you VM. There are SSM configurations present, meaning it is enabled. Should I remove them or leave them?

Sergiu.Daniluk · ‎05-12-2020

Can you share which config you are referring to?

alanraczek11 · ‎05-12-2020

alanraczek11 · ‎05-12-2020

Sorry, I have more questions I should have asked, I'm not a Cisco guy.

"What is the IGMP version running on your srv/receivers? Depending on this, you can adjust the version on your switch as well."

Is this to imply that IGMP running on the servers/applications are probably written to support a certain IGMP? Thus match that on the switches?

THank you.

Sergiu.Daniluk · ‎05-12-2020

On different OS systems you have the option to enable a specific version of IGMP or leave it on auto and will respond to queries depending on the version of queries.

Regarding the config, it seems you have the SVI enabled with PIM. It could be for the purpose of acting as query - tihs can be checked if the IP listed as querier is actually the IP of the SVI. Although as I see you have a Nexus switch, you can enable the query function directly from the vlan:

 switch(config)# vlan vlan-id 
 switch(config-vlan)# ip igmp snooping querier IP-address

Summary: if you are absolutely sure that you do not need to route for your mcast traffic, then you can remove the PIM functionality. But before that, configure the IGMP snooping querier as mentioned above.

If you have the switch configured in vpc, configure the snooping on both peers. I think you will get a message mentioning this anyway once you configure it.

Cheers,

Sergiu

alanraczek11 · ‎05-13-2020

" it seems you have the SVI enabled with PIM" , how do you know this ? Sorry, I'm really not understanding. What is throwing me is we are talking about queriers when we have a SSM configuration present. But back to the querier.

"this can be checked if the IP listed as querier is actually the IP of the SVI". So you mean check the VLAN ip? How do I know where the VLAN originated?

I have tried the mtrace command but I can't be sure of parameters I am entering.

Tried igmp join-group: 239.0.0.1 is the UDP group, for source I used source IP of video srv 44, I was trying to add destination , dest being IP of user workstation receiving udp 18. I don't see any UDP broadcast even with debug.

mtrace (10.16.16.2 is the core switch)

Honestly not sure what this is telling me.

I was a systems admin for 20+years on Windows, not a lot of detailed work on switches so I am sorry if I am ignorant.I know how to do things in switches but the theory I am hazy on. I am in a bind to get this fixed. I am tempted to rip all config out and redo. Thank you very much.

alanraczek11 · ‎05-13-2020

ALso the igmp querier seems to be 10.16.16.8, which is actually an interface on the CORE switch.

alanraczek11 · ‎05-15-2020

Anything??

Sergiu.Daniluk · ‎05-13-2020

Hi,

" it seems you have the SVI enabled with PIM" , how do you know this ? Sorry, I'm really not understanding. What is throwing me is we are talking about queriers when we have a SSM configuration present

The "ip pim sparse-mode" is what I was referring to. Your SVIs are configured with PIM.

What is throwing me is we are talking about queriers when we have a SSM configuration present.

We are talking about queries since this is important in a L2 environment where IGMP snooping is enabled. Without IGMP membership queries, the switch will not program the output interfaces in the snooping table.

"this can be checked if the IP listed as querier is actually the IP of the SVI". So you mean check the VLAN ip? How do I know where the VLAN originated?

Sorry about my not so good phrasing. I was trying to ask you to verify who is the querier, but you answered later.

I have tried the mtrace command but I can't be sure of parameters I am entering.

This is a good explanation of the command: https://cciethebeginning.wordpress.com/2011/07/17/multicast-mtrace-command/

When trying to ping a multicast group, use "ping multicast <group> source <source-ip>" command. You were missing the multicast kw

I was a systems admin for 20+years on Windows, not a lot of detailed work on switches so I am sorry if I am ignorant.I know how to do things in switches but the theory I am hazy on.

No worries. We got your back! ^_^

I am in a bind to get this fixed. I am tempted to rip all config out and redo.

Maybe you can describe us what exactly is the problem. This way, we can have a closer look at the actual problem. Some commands which can help us along:

  show ip igmp snooping vlan X
  show ip igmp snooping querier detail 
  show ip igmp groups summary 
  show ip igmp groups vlan X
  show ip igmp groups X.X.X.X    
  show ip igmp snooping mrouter

Cheers,

Sergiu

alanraczek11 · ‎05-13-2020

Thank you so much! First a pictorial description:

Now the output you requested, all from TOR4 or the source of "bad" video feed. Was not sure of what IP for:

show ip igmp groups X.X.X.X

TOR4# sho ip igmp snooping vlan 110
IGMP Snooping information for vlan 110
IGMP snooping enabled
Lookup mode: IP
IGMP querier none
Switch-querier enabled, address 10.16.16.2, currently not running
IGMPv3 Explicit tracking enabled
IGMPv2 Fast leave disabled
IGMPv1/v2 Report suppression enabled
IGMPv3 Report suppression disabled
Link Local Groups suppression enabled
Router port detection using PIM Hellos, IGMP Queries
Number of router-ports: 2
Number of groups: 13
VLAN vPC function disabled
Active ports:
Eth1/10 Eth1/18 Eth1/19 Eth1/21
Eth1/31 Eth1/46 Eth1/49/1 Eth1/49/2
Eth1/49/3 Eth1/49/4 Eth1/51/1 Eth1/51/2
Eth1/51/3 Eth1/51/4 Eth1/54
Report Flooding: Disabled
Interfaces for Report Flooding: n/a
Use Group Address for Proxy Leaves: no

TOR4#

TOR4# show ip igmp snooping querier detail
Vlan IP Address Version Expires Port
80 10.16.14.11 v2 00:03:51 Ethernet1/54
IGMP snooping querier configuration for VLAN 80
IGMP snooping last member query count: 2, configured value: 2
IGMP snooping version: 2, configured value: 3
IGMP snooping robustness variable: 2, configured value: 2
IGMP snooping startup query count: 2, configured value: 2
IGMP snooping startup query interval: 31 secs, configured value: 31 secs
IGMP snooping last member query interval: 1 secs, configured value: 1 secs
IGMP snooping query interval: 125 secs, configured value: 125 secs
IGMP snooping query max response time: 10 secs, configured value: 10 secs
IGMP snooping configured querier timeout: 255 secs, default
128 128.244.220.1 v3 00:03:04 Ethernet1/54
IGMP snooping querier configuration for VLAN 128
IGMP snooping last member query count: 2, configured value: 2
IGMP snooping version: 3, configured value: 3
IGMP snooping robustness variable: 2, configured value: 2
IGMP snooping startup query count: 2, configured value: 2
IGMP snooping startup query interval: 31 secs, configured value: 31 secs
IGMP snooping last member query interval: 1 secs, configured value: 1 secs
IGMP snooping query interval: 125 secs, configured value: 125 secs
IGMP snooping query max response time: 10 secs, configured value: 10 secs
IGMP snooping configured querier timeout: 255 secs, default
TOR4#

TOR4# show ip igmp groups summary
VRF-name (*,G)-Count (S,G)-Count
default 13 0

TOR4#

TOR4# show ip igmp groups vlan 110
IGMP Connected Group Membership for Interface "Vlan110" - 12 total entries
Type: S - Static, D - Dynamic, L - Local, T - SSM Translated
Group Address Type Interface Uptime Expires Last Reporter
224.4.205.58 D Vlan110 1w1d 00:04:17 10.16.16.44
224.4.205.59 D Vlan110 1w1d 00:04:02 10.16.16.44
224.4.205.60 D Vlan110 1w1d 00:04:18 10.16.16.44
224.4.205.61 D Vlan110 1w1d 00:04:02 10.16.16.44
239.0.0.1 L Vlan110 1w1d never 10.16.16.8
239.0.12.10 D Vlan110 24w5d 00:04:17 192.168.146.10
239.0.12.11 D Vlan110 24w5d 00:02:40 192.168.146.10
239.0.12.12 D Vlan110 24w5d 00:04:19 192.168.146.10
239.0.12.13 D Vlan110 24w5d 00:02:33 192.168.146.10
239.0.12.14 D Vlan110 24w5d 00:04:17 192.168.146.10
239.0.12.15 D Vlan110 24w5d 00:02:35 192.168.146.10
239.255.255.250 D Vlan110 45w0d 00:04:17 10.16.16.191

TOR4#

TOR4# show ip igmp groups 10.16.16.44
IGMP Connected Group Membership for VRF "default" - matching Source "10.16.16.44"
Type: S - Static, D - Dynamic, L - Local, T - SSM Translated
Group Address Type Interface Uptime Expires Last Reporter

TOR4# show ip igmp groups 10.16.14.14
IGMP Connected Group Membership for VRF "default" - matching Source "10.16.14.14"
Type: S - Static, D - Dynamic, L - Local, T - SSM Translated
Group Address Type Interface Uptime Expires Last Reporter

TOR4# show ip igmp groups 10.16.14.8
IGMP Connected Group Membership for VRF "default" - matching Source "10.16.14.8"
Type: S - Static, D - Dynamic, L - Local, T - SSM Translated
Group Address Type Interface Uptime Expires Last Reporter

TOR4#

TOR4# show ip igmp snooping mrouter
Type: S - Static, D - Dynamic, V - vPC Peer Link
I - Internal, F - Fabricpath core port
C - Co-learned, U - User Configured
P - learnt by Peer
Vlan Router-port Type Uptime Expires
80 Vlan80 I 1y18w never
80 Eth1/54 D 45w0d 00:04:47
110 Vlan110 I 1y18w never
110 Eth1/54 D 45w0d 00:04:53
128 Eth1/54 D 45w0d 00:03:41

TOR4#