Cisco Nexus 3548 Multicast Sender Host and Receiver in same switch

[rehadiri]

Hello ,

We have the following network setup as a minimal multicast testing environment. Please don't bother about 194.x.x.x ip addresses used in the intranet.

Udp sender host can send the udp multicast to the interface ethernet 1/36 and Udp receiver host can successfuly join the multicast group, but udp multicasts are never reaching either Vlan401 and Udp receiver host.

Thank You For Your Help 

[rehadiri]

Some more information and a correction

Correction : The interface address of 1/36 is actually 194.0.142.147/28 ( not 192.142.0.146 ) . This a typo error of me. Actually its correct

The version of the switch is : nxos.9.2.2.bin

[rehadiri]

I have changed the interface 1/36 to switchport and included to VLAN 401. And i have set the sender ip address from that VLAN 401. 

Multicasting works fine if everthing in the same VLAN. 

[Jon Marshall · Accepted solution]

Not sure what software you are using to test with but check the TTL of the packets. 

It obviously needs to be > 1 if you are routing between directly connected subnets. 

Jon

[rehadiri]

This is special testing application written in Python . I have a sender application and a receiver application. I don't know how to check TTL.

The sender application is sending 20 bytes of test packet from the port 5007 to the receiver every 0.5 seconds continuously.

[Jon Marshall]

You could capture the packets to see what the TTL is set to. 

Jon

[rehadiri]

Yes , you are correct

I have modified the python multicast sender application code as below. 

MULTICAST_TTL = 5

sock.setsockopt(socket.IPPROTO, IP,socket.IP_MULTICAST_TTL, MULTICAST_TTL)

and it worked !

Thanks

[Elliot Dierksen]

Do you have multicast routing enabled globally? I suspect not. Depending on the platform, that will be either "ip multicast-routing" or "ip multicast-routing distributed".

[rehadiri]

I don't know how to set ip multicast-routing or ip multicast-routing distributed in the nx-os nxos.9.2.2.bin. It looks that this version of OS doesn't have these global commands. The only global multicast command that is active is  :

 ip multicast multipath s-g-hash next-hop-based 

[Elliot Dierksen]

You did say Nexus, but somehow I missed that. First, you need "feature pim" in global config. This guide says 9K, but I suspect it should be relevant to the 3548 depending on the version. I have done multicast in various routers and switches, but not in a Nexus to this point.

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/7-x/multicast/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide_7x/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide_7x... 

[rehadiri]

Two features are enabled in the 3548

- Feature interface-vlan

- Feature pim

Thanks