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Tutorial: Allow UDP Multicast and IGMP to Pass Through

Abstract

Access Server transfers information by unicast. Follow these steps to change this and allow UDP multicast and IGMP to pass through.

Overview

This tutorial guides you through switching from unicast (Access Server's default data transfer) to allowing UPD multicast and IGMP. This is done with the configuration key, vpn.routing.allow_mcast.

Access Server blocks multicast or broadcast traffic. Follow these steps to lift that restriction.

Prerequisites

  • An installed Access Server.

  • Console access with root privileges.

Step 1: Allow UDP multicast and IGMP to pass through

  1. Connect to the console with root privileges.

  3. Allow UDP multicast and IGMP traffic to pass through:

    ./sacli --key "vpn.routing.allow_mcast" --value "true" ConfigPut
./sacli start

    • This setting implements these iptables rules on the VPN server, which is what allows the traffic to pass through:

      ACCEPT udp   -- anywhere  base-address.mcast.net/4 udp
ACCEPT igmp  -- anywhere  anywhere
ACCEPT udp   -- anywhere  base-address.mcast.net/4 udp
ACCEPT igmp  -- anywhere  anywhere

  4. To restore the default setting (and again restrict UDP multicast and IGMP traffic):

    ./sacli --key "vpn.routing.allow_mcast" ConfigDel
./sacli start
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