13 votes

Stateful matching of multicast responses in iptables

With recent Linux kernels (>= 2.6.39) you can use kernel's ipset to workaround limitation of connection tracking. You do not need to write any userspace or kernel helper. For UPnP SSDP it can be ...
  • 173
13 votes
Accepted

Use ip route add to add multicast routes to multiple interfaces

That you have multicast going through your Linux box by using unicast routing is a combination of a couple of lucky circumstances. Multicast routing is not the same as unicast routing. Unicast ...
  • 3,158
7 votes

Troubleshooting UDP multicast on Windows

If you have a VirtualBox Host-Only Ethernet Adapter activated on your system that might be the problem, which it was for me, so try disabling it. See https://www.virtualbox.org/ticket/8698.
6 votes

Linux Kernel not passing through multicast UDP packets

TL/DR Also make sure your multicast doesn't come from a vlan. tcpdump -e would help determine if they do. In all fairness, somebody ought to build a page with a checklist of things that can prevent ...
6 votes

How to make sysctl network bridge settings persist after a reboot?

I also have this problem on Ubuntu 14.04.1 net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 Are not set on reboot!!! I have to ...
  • 71
6 votes

Do all ethernet switches support multicast?

Yes, even unmanaged "bargain" switches will likely have some minimal support for multicast, to the extent that a host connected to the switch will be able to receive a multicast stream. Look at the ...
4 votes

Do all ethernet switches support multicast?

Simple switches treat multicast like broadcast[*], as least as far as I have seen. Therefore, multicast will reach its destinations but may cause unnecessary traffic since it's forwarded to ...
  • 8,664
4 votes
Accepted

Why 224.0.0.1 traffic is filtered by Linux hosts?

I am understanding your question so that you would like to block processing of broadcasts, but not of multicasts, due to possible broadcast security threats. That leads to the question why you ...
  • 519
3 votes

How many available IPv6 multicast prefixes are there?

Your question doesn't make a lot of sense... there's no concept of "prefixes" in IPv6 multicast. The base RFC defines an IPv6 multicast address as looking like this: | 8 | 4 | 4 | ...
  • 95k
3 votes
Accepted

Hyper-V Windows hosts see/count multicast traffic that they shouldn't

If you're using a NIC that doesn't support VMQ, or if you have VMQ disabled, then the NIC must be placed in promiscuous mode, which leads to the behavior that you're seeing.
  • 5,116
3 votes
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What interaction is required for a Windows server and Cisco router to setup and destroy a Multicast session?

1: Can anyone tell me how a machine "registers" with the router to say it wants to be part of a multicast group? This is done with the Internet Group Management Protocol (IGMPv1, IGMPv2 and ...
3 votes
Accepted

Keepalived: multicast vs unicast

Q1. I wonder if multiply VRRP routers can flood the network with multicast advertisement and cause some performance issue? Would you recommend to use unicast in this case? No sane amount of VRRP ...
3 votes

Unable to ping multicast IP

You can only ping, via multicast, hosts which are subscribed to the multicast group which you are pinging. You need to be careful about which multicast groups you use, and, in general, you should use ...
  • 3,158
3 votes
Accepted

Office 365 Skype/Lync: Support for stream multicast or mirroring?

No, each client has its own stream. Keep in mind Office365 Skype for Business uses a server in the cloud not on premises. Essentially what you are asking is can Skype for Business detect you are all ...
  • 2,900
3 votes
Accepted

OS X network stack ignores IGMP membership queries

The problem is shown in the first packet capture, where you will notice that the IGMP group join packet is an IGMPv2 packet, but the responses from the IGMP querier are all v3. This may seem fine, ...
2 votes

Multicast File Transfers

uftp is working for me. I ended up maxing the "robust" -s option to 50, and opening the server firewall to the ip's of the clients for the registration phase.
  • 143
2 votes

How can I test Multicast UDP connectivity between two servers?

If one server is already listening on multicast (netstat -g will tell you if it is). You can broadcast with normal netcat, and detect with tcpdump. Send a fixed size message to the multicast address. ...
  • 594
2 votes

Is IPv6 multicast routable over the Internet?

I see multiple answers assuming you have mistaken what multicast is. You have made no mistake and your question is clear. I asked this question to myself: Can I multicast across the IPv6 Internet? ...
  • 194
2 votes

Multicast and duplicate IP addresses

No. Multicast packets are sent to a special address where only the devices in the group are listening at. This is independent of your main (unicast) IP address. The multicast IP address is tied to ...
  • 5,652
2 votes
Accepted

Peer to peer communication in complicated multi-subnets LAN

I wrote few peer-to-peer application and I can tell you that reachability of peers is the main problem with this kind of applications. Here are few pointers: if you use TCP your only hope is UPnP. ...
  • 4,579
2 votes
Accepted

Who is reached by IP multicast?

Unicast is visible to the local LAN AND it is visible to any routable network that has a chain of properly configured multicast repeaters available. NO internet provider will forward multicast ...
  • 50.9k
2 votes

UDP multicast send/receive: Routing or socat issues?

It turns out it is a routing problem on the switch. Multicast routing for the VLAN in 10.1.1.x is not turned on. Once we added 'pim sparse-mode' on our cisco router. Everything is working as ...
  • 245
2 votes
Accepted

Multicast for Tomcat servers on Google Cloud

You can use overlay network deployment to have mcast/bcast support inside. "Third-party partner solutions such as Weave Net, Cohesive Networks, or Ravello can help you enable these features by using ...
2 votes

Multicast for Tomcat servers on Google Cloud

I think it’s better to use static cluster. There are 2 types of cluster: Static Tomcat Cluster Dynamic Tomcat Cluster In static cluster there is not need multicast, because each tomcat we ...
2 votes
Accepted

Multicast not working on macvtap device

I found an answer at Superuser: https://superuser.com/questions/944678/how-to-configure-macvtap-to-let-it-pass-multicast-packet-correctly/1033768#1033768 I'll just copy sourcejedi's answer here: ...
2 votes
Accepted

How to make reverse mDNS through IPv6 on OSX?

I found a couple of ways to do this, but they're both a bit ugly. First, you can use dns-sd -q and specify the ptr record type... but you need to convert the address you want to look up into nibble-by-...
2 votes
Accepted

Using multicast DNS to broadcast name of my machine like raspberrpi does

rPI uses the Avahi application for mDNS. You would need to install that on your devices.
  • 2,149
2 votes
Accepted

How do multicast addresses on the public internet resolve

No, 255.0.0.1 is neither the Limited Broadcast address nor a multicast address. Multicast addresses are in the 224.0.0.0/4 range, and the Limited Broadcast address is the 255.255.255.255 address. ...
  • 3,158
1 vote
Accepted

One of two machines on same network doesn't receive multicast group memberships

switch to IGMPv2 on Ubuntu echo "2" > /proc/sys/net/ipv4/conf/eth1/force_igmp_version and try againt. If you have same problem than check Reverse Path filtering cat /proc/sys/net/ipv4/conf/...
  • 1,598
1 vote
Accepted

When a host joins a multicast group, does it needs to change its ip address to the multicast group's ip address?

No. And, IP multicast addresses have a special range (e.g. 239.x.x.x) that would be illegal as a host address. You just do the setsockopt with IP_ADD_MEMBERSHIP and you're done. And, if you really ...

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