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Multicast delay across 3750X, 6509, 4510 L3 switches


we have a new vendor installed radio system that runs on software installed on a console pc.  When you key the microphone that is connected to the console pc, it sends a multicast to the gateway transmitter that is located in another part of the building, across several L3 switches.  There is about a 3-4 second delay from when the microphone is keyed until you can start talking.  Voice quality is good - the only problem is the delay.  To rule out a problem with the radio system, I temporarily installed the console pc on the same switch as the gateway transmitter - no delay when keying up the mic in this L2 environment.  Unfortunately the console pc needs to be in another part of the building otherwise I would leave it this way.  Any ideas on what the problem is?

A brief overview of the connectivity - the console pc is connected to a 3750X switch - the 3750X has two L3 uplink connections to two separate 6509 distribution switches.  The two 6509 switches have two separate L3 connections to a 4510 switch, which is what the gateway transmitted is connected to.  IP multicast is enabled on all switches and seems to work fine for music on hold for the VoIP phones.



  • LAN Switching and Routing