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souzader
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Enthusiast

multicast

Hi Experts,

Does anyone know to enable MDNS packet traffic on the NSX-T(3.1) T0 and T1 routers for a vlan?

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bmcb555
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Have you enabled your T1/T0 routers to pass multicast traffic?

https://docs.vmware.com/en/VMware-NSX/4.1/administration/GUID-6AAC3360-4F79-4FBF-BCC1-0D8C220B0621.h...

Like most multicast routing it has it's own setup, depending on your setup you may need to configure it on your Nexus as well to route.

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souzader
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Hi @bmcb555 

I saw this document but since it's version 4.x, I thought it wouldn't apply to 3.x.

Have you already done this type of configuration? Do you know if I can do it in production?

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bmcb555
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Here you go - https://docs.vmware.com/en/VMware-NSX-T-Data-Center/3.2/nsxt_32_admin.pdf

Have I configured multicast, yes. With NSX, no. The concept of multicast PIM and RP isn't locked down to a specific vendor, my experience with multicast is via Cisco but the concepts are the same. 

NSX supports PIM Sparse Mode with IGMPv2 so I would probably configure the t0 (assuming both subnets terminate to the same t0) as a static RP for the traffic. Use that as your target/receiver. 

here is some additional information on sparse mode https://networklessons.com/multicast/multicast-pim-sparse-mode

I have implement multicast into production networks, nothing to really note. 

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andrewassis
Contributor
Contributor

Enabling MDNS (Multicast DNS) packet traffic on NSX-T routers for specific VLANs can involve several steps. NSX-T provides features for controlling and allowing multicast traffic, but you'll need to ensure that your configuration is correct to permit MDNS traffic to flow between segments and devices on different subnets. Here are some steps and considerations to help you troubleshoot and configure MDNS support in NSX-T:

1. **Verify NSX-T Multicast Configuration:**
- Check if multicast is configured correctly on NSX-T. Ensure that IGMP Snooping and PIM (Protocol Independent Multicast) are properly configured on the NSX-T routers.
- Make sure that multicast is enabled on the segments where MDNS traffic needs to be allowed.

2. **Check for Block Rules:**
- Review the NSX-T firewall rules to check if there are any rules that might be blocking MDNS traffic. Look for rules on both the T0 and T1 routers that may be impacting MDNS traffic flow.

3. **Create Firewall Rules:**
- If you don't have specific firewall rules in place to allow MDNS traffic, you may need to create them. Configure rules that permit UDP traffic on port 5353 (the standard MDNS port) between the source and destination segments or subnets.

4. **MDNS Gateway Configuration:**
- Ensure that the MDNS Gateway feature is configured correctly. The MDNS Gateway should be attached to the appropriate segments and subnets where MDNS traffic needs to be allowed. Verify that it's correctly listening for MDNS traffic.

5. **Monitoring and Troubleshooting:**
- Use NSX-T monitoring tools and logs to trace the flow of MDNS packets. Check for any drop or deny events in the NSX-T logs that may indicate the packets are being blocked.
- You can also use packet capture tools or Wireshark to capture MDNS traffic at various points in your network to see if it's reaching the expected destinations or being blocked.

6. **Contact VMware Support:**
- If you are unable to identify the issue and resolve it through the above steps, consider reaching out to VMware support for assistance. They can provide specific guidance for your NSX-T version and configuration.

7. **Documentation and Vendor Support:**
- Consult the official VMware NSX-T documentation for your specific version to ensure that you're following recommended practices for multicast and MDNS support.
- Check with your radio system vendor to ensure that their equipment and software are compatible with NSX-T and that they have any specific configuration requirements for MDNS.

It's worth noting that MDNS traffic can be tricky to manage in virtualized network environments like NSX-T due to its multicast nature. Proper configuration and troubleshooting are essential to ensure that MDNS packets can flow between segments and devices on different subnets. Be sure to backup your configuration before making any significant changes, and consider testing changes in a controlled environment before applying them to a production network.