Multicast Issue on Catalyst Devices

Software
1

The Issue

Adding a sensor in multicast mode directly to a Catalyst DHCP-provisioned port will fail and get the sensor stuck in the INITIALIZING state.

Root Cause

The Catalyst port’s DHCP configuration lacked the required gateway address (option routers). Without a gateway, the sensor couldn’t correctly route its multicast discovery packets.

The Fix

Modify the DHCP server configuration file (/etc/dhcp/dhcpd.conf) to include the gateway.

Note: All addresses (subnet, range, option routers) in this code snippet are examples and must be updated to reflect your actual network topology.

Bash

subnet 10.125.21.0 netmask 255.255.255.0 {
        range 10.125.21.2 10.125.21.22;
        option routers 10.125.21.1; 
}

Restart the DHCP service on the Linux host (Ubuntu/Debian):

Bash

sudo systemctl restart isc-dhcp-server
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