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Devices in a security zone can't reach Chromecast in another zone using Multicast

Hello,

 

I have a Google Chromecast connected to a subnet/VLAN in the Sophos XG105 firewall and my Workstations on another subnet on the same firewall. In order for the workstations to find the Chromecast, they send packets to the multicast IP 239.255.255.250 port 1900 (UDP) however, these packets are being blocked by the firewall.

 

I've enabled Multicast Routing under Configure > Routing and added some multicast routing statements for specific IPs in my LAN zone (where the workstations are) but the multicast packets are being blocked by the firewall. The Rule ID hit, according to the Log viewer, is ID 0 which is the implicit deny at the end of the rule list because it couldn't match any other rule.

 

I did add a rule allowing all traffic from my LAN zone to the zone where the Chromecast is but it's still being blocked. My guess is that the firewall doesn't know that the destination IP, 239.255.255.250 is part of the destination zone and that's why it doesn't hit any rule but I'm not sure if this is correct.

 

Does anyone know what could be wrong in this case?

 

Regards,

 

 



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  • Hi Andres,

    please post a full copy of the rule. The issue is more than likely the setup of the firewall rule.

    Also please post a copy of the error messages from logviewer.

    In the firewall rule what do you have enabled for IPS, Application  and web?

     

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

Children
  • Here's the screenshot of the rule:

     

     

    And the log viewer

     


     

    The rule doesn't have IPS or any other type of filtering enabled.

     

    Thanks

     

    Andres

  • Try again, last post crashed.

    The XG does not know what to do with the multicast packets. Try changing your rule so the the IP  address of your chromecast box is used instead and also try changing the destination zone to LAN.

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • The destination IP is the multicast address so what would changing the rule to the Chromcast's IP do in this case? The firewall won't match the packet with that rule because the IP doesn't match.

     

    I can't change the destination zone to LAN because the Chromecast is not in this zone. Even if I change the destination zone to the Chromecast one, it still denies the packet.

     

    Andres

  • Hi Andres,

    you are confusing a couple of things. LAN is the internal definition of the networks unless you are using DMZ. LAN usually has all your internal networks if you check the NETWORK tab, ZONES. Any means you are trying to broadcast out your WAN interface which is usually considered a security risk.

    Please try putting the chromecast box IP address in the destination network.

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • Hi Ian,

     

    thanks for that. The Chromecast is in its own Zone called "IoT" and it's of the type "LAN". I've changed the rule to specify the destination zone to the IoT and the destination network to be the Chromecast unicast IP or the multicast IP as well.

     

    Unfortunately, the firewall is still blocking the traffic.

     

    Andres

  • Hi Andres,

    with the rule changes what do you see in logviewer?

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • The same thing as before. The firewall rule matched is 0 (implicity Deny) with the Log Component saying "Appliance Access" when trying to reach the 239.255.255.250 address. Here's a screenshot.

     

     

    Andres

  • Hi Andres,

    as a test change your firewall rule to 

    Source LAN network any destination LAN network any allow any protocol - log.

    Then review the logs to see what is actually being passed 

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.

  • Hi Ian,

     

    still no good. Same thing seen in the log viewer. Is it possible that the problem is that the firewall can't match the destination IP 239.255.255.250 to a network on any of the zones which is why it wouldn't match any rule and deny the packet?

     

    Andres

  • Hi Andres,

    the firewall will never match that to a network, it is a broadcast (multicast) address. 

    Okay, I checked the web setup for chromecast, it only works with tablets and mobile phones. You  need to be on the same network as the chromecast device and it needs to be connected to a TV via USB.

    I hope that helps.

    Ian

    XG115W - v19.5.1 mr-1 - Home

    If a post solves your question please use the 'Verify Answer' button.