Ipv6 multicast being blocked on lan?


  • LAYER 8 Global Moderator

    So maybe I have missed them but have noticed stuff like this now

    block
    Aug 12 10:41:42 LAN [fe80::794f:b5ca:8dc7:92d7]:52956 [ff02::1:3]:5355 UDP

    block
    Aug 12 10:41:38 LAN [fe80::794f:b5ca:8dc7:92d7]:63672 [ff02::c]:1900 UDP

    Might have been going on for quite some time and just now noticed, but shouldn't lan rule

    IPv6 * LAN net  as source to * destination allow for this?

    If not what rule needs to be put in to allow?



  • port 1900 udp is upnp iirc. and i think 5535 is bonjour of sorts. not too sure about that one.

    The ff02:: range is a special range which is not covered by the LAN rule. LAN net expands to the global address and not the link local address of that interface.

    The ff02 is a multicast address used for registering routers and dhcp servers etc. You'd need to look that specific address up for what service it is.


  • LAYER 8 Global Moderator

    5355 is LLMNR, I have turned it off in group policy on the machine sending it.. I personally have no use for it ;)  and I clearly don't need SSDP either so turning that crap off as well ;)

    But I think I more curious why this traffic is being logged, but why no ipv4 multicast is being logged.. I would assume its blocked as well?  Or does lan net include the ipv4 multicast?

    isn't all traffic that is blocked by the default rule logged?  So it must be allowing multicast on ipv4?  But not on ipv6 link-local addresses?



  • are u using windows 7? it prefers ipv6 over ipv4 from what i can tell…its probably not sending any ipv4 out since ipv6 is working on your network....



  • @johnpoz:

    isn't all traffic that is blocked by the default rule logged?  So it must be allowing multicast on ipv4?  But not on ipv6 link-local addresses?

    exactly. Your LAN rules aren't permitting your link local sourced traffic, where with v4 they're sourced from a LAN IP which is permitted. Granted it's not forwarding that multicast traffic, but it's not blocking it either with v4.


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