Multicast on LAN doesn't work - 3750

[Bilal Nawaz]

Hello, I have PC_A and PC_B connected to the same switch, and are put in the same vlan. PC_A is the master (source) and PC_B is the destination (client).

IGMP Snooping is enabled by default.

Is there any reason why this should fail? There is no RP or any interface with PIM enabled. Its a flat network with a source and client in the same vlan...

IH-3750-LOADTEST-101#show ip igmp snooping vlan 724

Global IGMP Snooping configuration:

-------------------------------------------

IGMP snooping              : Enabled

IGMPv3 snooping (minimal)  : Enabled

Report suppression         : Enabled

TCN solicit query          : Disabled

TCN flood query count      : 2

Robustness variable          : 2

Last member query count      : 2

Last member query interval : 1000

Vlan 724:

--------

IGMP snooping                       : Enabled

CAPWAP enabled                      : Disabled

IGMPv2 immediate leave              : Disabled

Multicast router learning mode      : pim-dvmrp

CGMP interoperability mode          : IGMP_ONLY

Robustness variable                 : 2

Last member query count             : 2

Last member query interval          : 1000

IH-3750-LOADTEST-101#show ip igmp snooping mrouter

Vlan    ports

----    -----

724    Gi1/0/1(dynamic)

Any guidance is much appreciated.

Please rate useful posts and remember to mark any solved questions as answered. Thank you.       

[Reza Sharifi]

Hi,

Since you have source and receiver in the same vlan, there is no need for PIM.

Are you using the same Multicast address for the source and receiver?

Are you using VLC to test?

HTH

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

When you have IGMP snooping enabled, you need an IGMP querier.  Enable PIM on the interface with the multicast source and recipient(s).

[Reza Sharifi]

Joe,

You can't enable PIM on a layer-2 interface (access port).

Reza

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Reza Sharifi wrote:
 Joe,
You can't enable PIM on a layer-2 interface (access port).
Reza

Ah, I wasn't clear, I meant the SVI interface, not the physical port.

[Bilal Nawaz]

So I've failed to mention the testing I did. This is 3 environments. Production, non production, my own lab. This is to do with PC builds. A deployment server sends unicast build to a PC, and the PC on LAN waits for clients to join to share the image with, and they all build.

Multicasting works in production, it has RP and using sparse mode. All good.

Non production is where the problem is. Flat vlan, no RP no pim enabled. All one vlan stretched across sites (OTV).
As far as I'm concerned it should work since its on the same vlan.
So I took the test even further to test if it works on the same switch within vlan 724. It doesn't work.

If I move these PCs to my own lab where I have a flat network with a 3560 giving out addresses to these clients (on the same LAN) it works.

So I have taken out the fact that it is OTV that has anything to do with it since its all on the same switch. So it's really puzzled me somewhat....

Sent from Cisco Technical Support iPhone App

[Bilal Nawaz]

Would it be this? Because I have a feeling this is what is causing it to break...

IH-3750-LOADTEST-101#show ip igmp snooping mrouter

Vlan    ports

----    -----

724    Gi1/0/1(dynamic)

Because its just meant to be a flat vlan, why would the switch say this is an mrouter port for this vlan (the route towards the RP in production is towards that way) There is no way for the two to talk to each other since production and non production aren't routed between each other.

If so, how do I stop this for this vlan only - I dont want it to be 'dynamic' I want this to be nothing....?

I think with another test lab that I did really quickly in GNS3, there is no mrouted port and I've been reading this doco and mentions, if a mrouted port is there, the interesting traffic is sent out of this interface towards an mrouter? I dont want this to happen though. Just tested in GNS too:

The only devices with IP addresses are Master and Client, everything else is in vlan 1.

I have a master and I am ping'ing 234.1.1.1 (generating the source) and have a join group on the client. It's able to join and pings are successful.

When I look on R1 or R2 during this ping and multicast joins... I see nothing for 'mrouted port'

So am i right in saying that this R1 and R2 are not participating in this igmp process - this is normal behaviour since everything is on the LAN (vlan 1)? If not are there any useful debugs I can run to see if anything is occuring...

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008059a9df.shtml

This document says:

Basically, when the switches learn or statically know about an mrouter port, two critical things occur:
The switch "relays" the IGMP reports from the receivers to the mrouter port, which means that the IGMP reports go toward the multicast router. The switch does not relay all the IGMP reports. Instead, the switch sends only a few of the reports to the mrouter. For the purpose of this discussion, the number of reports is not important. The multicast router only needs to know if there is at least one receiver that is still interested in the multicast downstream. In order to make the determination, the multicast router receives the periodic IGMP reports in response to its IGMP queries.
In a source-only multicast scenario, in which no receivers have yet "joined" in, the switch only sends the multicast stream out its mrouter port.

Any thoughts/opinions/ideas on this?

Thank you

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[Reza Sharifi]

This is a very simple multicast scenario with 2 ports in the same vlan on the same switch and should work just fine since IGMP is enabled by default.

I actulay tried it on a 3750X the other day using VLC and it worked just fine.

Can you try to assign a static group and test again?

Also, if you are using VLC, after you connect the PCs to the switch ports, stop the vlc and start it again. I have seen it been an issue sometimes.

ip igmp static-group x.x.x.x

HTH

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

As I posted earlier, IGMP snooping switches rely on an IGMP querier.  Normally this is handled by multicast routers.

(NB: On LAN segments with IGMP snooping without a multicast routers, some vendors have a feature to enable IGMP quering on a L2 switch.)

If IGMP snooping is disabled, then you shouldn't need the IGMP querier as the multicast flow should be flooded to all ports within the same VLAN.

Remember what IGMP snooping does, it suppresses multicast streams to ports unless the port indicates it wants that multicast stream.  How does an IGMP snooper know the port wants mulitcast, by it watching for IGMP replies.  Remember in IGMPv1 clients can "silently" drop off, so only reoccuring replies shows they still want the multicast stream.

Better explanations: http://en.wikipedia.org/wiki/IGMP_snooping

and

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/IGMPSnooping.html#wp1071684

[Bilal Nawaz]

Agreed, should be simple. But the only difference I can see is the IGMP snooping mrouter output.

Im not able to do the 'ip igmp static-group x.x.x.x' command:

IH-3750-LOADTEST-101(config)#ip igmp ?

  filter           IGMP Filter Enable

  immediate-leave  Leave groups immediately without sending last member query, use for one host network only

  limit            IGMP limit

  profile          IGMP Filter Profile

  snooping         Global IGMP Snooping enable for Catalyst Vlans

  ssm-map          SSM mapping commands

  vrf              Select VPN Routing/Forwarding instance

I do get this though:

IH-3750-LOADTEST-101(config)#ip igmp snooping vlan 724 static 234.1.1.1 interface ?

  FastEthernet     FastEthernet IEEE 802.3

  GigabitEthernet  GigabitEthernet IEEE 802.3z

  Port-channel     Ethernet Channel of interfaces

In which case, which interface do I specify and why?

On my test Lab it works, as shown above (without  the mrouted port). But in the non production environment, the switch  does have an IGMP snooping mrouter port which is an uplink to the  distribution layer switch (learnt about, dynamically).

Since the non production environment isn't  routable in any shape or form there will be no RP or SVI pim enabled or  active in this segment. How can I stop this please?

When I try to enable ip igmp snooping querier I get this:

IH-3750-LOADTEST-101#show ip igmp snooping mrouter

Vlan    ports

----    -----

   1    Switch

304    Switch

316    Switch

328    Gi1/0/1(dynamic), Switch

724    Gi1/0/1(dynamic), Switch

Where vlan 724 is still showing the uplink to the distribution switch and also Switch? - Im yet to test the multicast with this change. Vlan 328 is production and has IP Pim SVI in that vlan. And multicast works in this vlan.

I just tried the query command on another switch with the same vlan presant and I get this:

SQP3-3750-141(config)#ip igmp snooping querier

IGMP Querier function cannot be operationally enabled on some VLANs because the required conditions have not been met.

What conditions?

SQP3-3750-141#show ip igmp snooping querier vlan 724 detail

Global IGMP switch querier status

--------------------------------------------------------

admin state                    : Disabled

admin version                  : 2

source IP address              : 0.0.0.0       

query-interval (sec)           : 60

max-response-time (sec)        : 10

querier-timeout (sec)          : 120

tcn query count                : 2

tcn query interval (sec)       : 10

Vlan 724:   IGMP switch querier status

--------------------------------------------------------

admin state                    : Disabled (state inherited)

admin version                  : 2

source IP address              : 172.25.4.141  

query-interval (sec)           : 60

max-response-time (sec)        : 10

querier-timeout (sec)          : 120

tcn query count                : 2

tcn query interval (sec)       : 10

operational state              : Disabled

operational version            : 2

tcn query pending count        : 0

When I do a show ip igmp snooping mrouter, I do not see vlan 724 at all, even though the vlan exists on the switch and ports are active in that vlan.

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[paul driver]

Hello Bilal

How are you getting on with this issue?

Having labbed this up myself , basic L2 setup, vlan 500, no svi, All works as expected? - as you have pointed out.

R1- 1.1.1.254
R2 - 1.1.1.1 + M/C 234.1.1.1

R1 (vlan500)-SW1-(trunk)-SW2 - R2 (vlan500) + M/C group

I tried the static-group option (ip igmp static-group 234.1.1.1) which didnt work, I guess the interface just switches M/C traffic and doesn't included itself as a member.

Regards the snooping querier - It  relies on obtaining an address from an SVI - but it my lab it wanst required.

So given that you do have an SVI - have your tried ip igmp snooping querier address x.x.x.x ( svi of the vlan you want igmp to traverse)

SW1#

interface Vlan500

ip address 1.1.1.12 255.255.255.

sh ip igmp snooping querier

Vlan      IP Address               IGMP Version   Port

-------------------------------------------------------------

1         1.1.1.11                 v2            Switch

500       1.1.1.11                 v2            Switch

sh ip igmp snooping querier vlan 500

IP address               : 1.1.1.11

IGMP version             : v2

Port                     : Switch

Max response time        : 10s

SW2#

interface Vlan500

ip address 1.1.1.12 255.255.255.

sh ip igm snooping querier

Vlan      IP Address               IGMP Version   Port

-------------------------------------------------------------

1         1.1.1.11                 v2            Fa0/19

500       1.1.1.11                 v2            Fa0/19

sh ip igm snooping querier vlan 500

IP address               : 1.1.1.11

IGMP version             : v2

Port                     : Fa0/19

Max response time        : 10s

SW1#sh ip igmp snooping mrouter
Vlan    ports
----    -----
   1    Switch
500    Switch

SW2#sh ip igmp snooping mrouter
Vlan    ports
----    -----
   1    Fa0/19(dynamic)
500    Fa0/19(dynamic)

res

Paul

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Thanks.

[Bilal Nawaz]

Hello Paul, thanks for your post.

The SVI was only to replicate what the Master and Client do on the network. So.... there are no SVI's that are doing any routing. Just a flat network... So im not sure if I fully understand if the ip igmp snooping querier address is relevant here - maybe it might be?

Here is a rough topology of how it is:

So I have 2 pc's on the non prod LAN one is master and one is a client, trying to do multicast, but doesnt work. On this Loadtest switch (3750) I have enabled ip igmp querier and this is the difference:

IH-3750-LOADTEST-101#show ip igmp snooping mrouter

Vlan    ports

----    -----

   1    Switch

304    Switch

316    Switch

328    Gi1/0/1(dynamic), Switch

724    Gi1/0/1(dynamic), Switch

In our labs - the lab I did too, I had no record of any vlan or ports, was just blank. Did you get this too?

So I think the switch knows of a RP or something out there that is interested in multicast, so all mcast sources gets sent towards the RP which is Gi1/0/1, is this correct to say? Or because IGMP snooping is enabled its received a stream from a port that its not really listening for mcast traffic, its expecting clients to be requesting.

So the switch tries to send toward the RP and it wont be able to get anywhere because the RP wont know how to get to this vlan, its not routed, its totally separate. Because im starting to get a feeling this is the case.

In my output from above, is there any way to stop 'dynamic' learning for vlan 724, because I just know it works without this since we've tested in labs...

:-) Thank you for your help so far guys

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[paul driver]

Hello

In our labs - the lab I did too, I had no record of any vlan or ports, was just blank. Did you get this too? = Yes I did even with an SVI active, but then when i enabled the snooping queirer I did get an port output for the igmp snooping mrouter

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

[Bilal Nawaz]

But when I do not have an SVI, in my case I do get a mrouter 'port' learnt dynamic, which is going towards production. Since environments are segregated it still has that entry for 724

724    Gi1/0/1(dynamic), Switch

There is no mrouter for vlan 724 here... Only for production.

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[glen.grant]

  See if this doc sheds any light on the issue. 

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008059a9df.shtml