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Orbi WiFi 7 RBE973
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MLD not working as expected with local link addresses and local list multicast

Richard-Chapman
Aspirant

MLD not working as expected with local link addresses and local list multicast

This might well be a miss understanding of how IPv6 works but I've asked around and other confurmed my thinking. This is in a pure IPv6 setup, I am not using IPv4 (other than the web admin).


1) I have 3 hosts, each using there local link IPv6 address.

2) Host A is sending packets to a local link scoped multicast group "ff02::3000"

3) Host B is sending packets to a local link scoped mulitcast group "ff02::3010"

4) Host C is running wireshark and can see all the packets from Host A and B. Host C has not subscribed to ither of the multicast groups.


I have followed https://kb.netgear.com/21999/How-do-I-configure-Multicast-Listener-Discovery-MLD-snooping-using-the-... as told too by chat and spend a number of hours playing around with other settings.

I can get C not to see any traffic if I disable MLD snooping (sometimes, it appears that the config might not apply)


I'm at a bit of a loss.  Anyone got an idea or is this a bug

 

Thanks

Model: XSM4316S | M4300-8X8FStackable Managed Switch with 16x10G including 8x10GBASE-T and 8xSFP+ Layer 3
Message 1 of 10
Retired_Member
Not applicable

Re: MLD not working as expected with local link addresses and local list multicast

Hi @Richard-Chapman ,                                                                                                                         

Welcome to the community! 

                                      

For further analysis,Could you please provide the tech-support file of the Switch:
How do I send tech-support files from my Managed Switch to NETGEAR community moderators?
https://kb.netgear.com/31439/How-do-I-send-diagnostic-files-from-my-Managed-Switch-to-NETGEAR-commun...

 

BTW:

Could you run below command in your switch console/telnet session?

1.show mldsnooping

2.show mldsnooping ssm groups


Regards,

EricZ
NETGEAR employee

Message 2 of 10
Richard-Chapman
Aspirant

Re: MLD not working as expected with local link addresses and local list multicast

Hi EricZ,

Sorry for the delay.  I've sent the files to switch_support after I factory reset the switch and applied the steps set out in my original post. Still seeing all traffic to C and C never joins the groups.

 

Output you requested

(M4300-8X8F) #show mldsnooping

Admin Mode..................................... Enable
Multicast Control Frame Count.................. 0
Interfaces Enabled for MLD Snooping............ None
VLANs enabled for MLD snooping................. 300

(M4300-8X8F) #show mldsnooping ssm groups

VLAN Source
ID Group Interface Reporter Filter Mode Source Address List
---- ---------------- --------- ---------------- ----------- -------------------
There are currently no entries in the table.

(M4300-8X8F) #

 

I've got a the big brother of this switch on my desk as well so will be testing that shortly.

 

Thanks

Model: XSM4316S | M4300-8X8FStackable Managed Switch with 16x10G including 8x10GBASE-T and 8xSFP+ Layer 3
Message 3 of 10
Retired_Member
Not applicable

Re: MLD not working as expected with local link addresses and local list multicast

Hi @Richard-Chapman 

 

I got your tech-support file, thanks!

 

I notice there is 4 up ports(1,2,7,10), so how abount connection to Host A/B/C.

And you running MLD Snooping on VLAN300, right? And only port(1,2,7) belong VLAN300. So which host is running MLD Server role? and Which host is running MLD Client role?

As in MLD Snooping feature, first the Client will send report packet to join Multicast Group, then the Server will send Multicast stream to different Groups, only the Client has joined the correct Group can receive the Multicast.

Due to there is no any Groups info when you run command 'show mldsnooping ssm groups', so please double chek if the Clients send out report packet to join Groups?

 

Then on all ports, there is no need to enable 'ipv6 pim'.

Message 4 of 10
Richard-Chapman
Aspirant

Re: MLD not working as expected with local link addresses and local list multicast

Hi EricZ

Port to hosts 1 = A, 2 = B & 7 = C  all on VLAN 300.  Port 10 is on VLAN 1 and used to admin the switch using the web interface & has nothing to do with the multicast traffic.

 

Using your terms A & B are Servers and C would be a Client.  In the setup I have running on my desk A is sending data to ff02::3000 and B is sending data to ff02::3001, C (had to switch PC's) is now inspecting all packets incoming (on port 7) using TcpDump and is seeing the data from A & B.  C has not joined the multicast groups at all.  In the multicast model I should not see any multicast traffic on port 7/C unless C has subscribed to the groups but it is.

 

As an experiment I switched to using static IPv6 addresses and none Link Local scoped multicast groups and I was seeing the same thing.

 

I didn't enable "ipv6 pim".  After the switch was factory reset I ran the Ezsetup (I forget the name of the command but it sets up basic info like whcih address to run the website on). Then logged into the website and configued following the link

 

 

 

Message 5 of 10
Richard-Chapman
Aspirant

Re: MLD not working as expected with local link addresses and local list multicast

I have just tried using a M4300-96X and I get the same issue.

Message 6 of 10
Retired_Member
Not applicable

Re: MLD not working as expected with local link addresses and local list multicast

Hi @Richard-Chapman 

 

MLD Snooping is used for IPv6 Multicast forwarding. So please make sure the Destination MAC and IP is Multicast range.

For example:

Host A is Server, Host B/C is Client;

1). Host B/C not send report packet to join Groups. then Host A send IPv6 multicast stream(DMAC=33:33:00:00:00:01, DIP=FF1E::1);

In this scenario, Host B/C cannot receive the IPv6 multicast stream due to no any client join the Group;

2). Host B send report packet to join Groups(DIP=FF1E::1, DMAC=33:33:00:00:00:01), then Host A send IPv6 multicast stream(DMAC=33:33:00:00:00:01, DIP=FF1E::1);

In this scenario, only Host B can receive the IPv6 multicast stream, Host C cannot receive any packet. And on switch run command 'show mldsnooping ssm groups' can display Groups member port include Host B.

 

Hope it helps!

 

Message 7 of 10
Richard-Chapman
Aspirant

Re: MLD not working as expected with local link addresses and local list multicast

No let me be very clear about this: IPv6 multicasting is broken on your ms4300 model range out of the box. 

 

1) You got my setup incorrect.  Using your client/server terms A/B are Servers & C is a client.  

2) I am fully aware how multicast works and in my setup I would expect C NOT to receive any packets untill I run an application that joins C to the multicast groups.

3) However I AM seeing multicast traffic being sent to C BEFORE it joins any multicast group.

4) I'm sending data to valid mulitcast addresses (ff02 is) and the Dest MAC address of said packets are correct.

 

My question is 1) Is there a configuration setting I have missed or 2) Is this a bug

 

 

 

Message 8 of 10
Retired_Member
Not applicable

Re: MLD not working as expected with local link addresses and local list multicast

Hi @Richard-Chapman 

 

Cloud you please provide the capture file on Host C, just want to check the IPv6 multicast packet that received in this port.

In my side, MLD Snooping feature working fine, not see any issue actually.

Message 9 of 10
LaurentMa
NETGEAR Expert

Re: MLD not working as expected with local link addresses and local list multicast

Hi @Richard-Chapman and @Retired_Member 

 

Thank you for your messages, please note we are escalating this issue internally. Our Tech Support, QA, Engineering and PLM teams will work together until resolution. I will come back to this thread when the issue is resolved and update the Community with the solution.

 

Thanks!

Message 10 of 10
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