In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source. Copies are automatically created in other network elements, such as routers, but only when the topology of the network requires ...

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3answers
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What is the difference between unicast, anycast, broadcast and multicast traffic?

I have never had the privilege of working in an environment that required complicated routing or if it did require it, it was handled upstream of me. I've always used very simple static routing ...
21
votes
4answers
1k views

Pushing Large Files to 500+ Computers

I work with a team to manage 500-600 rented Windows 7 computers for an annual conference. We have a large amount of data that needs to be synced to these computers, up to 1 TiB. The computers are ...
14
votes
5answers
17k views

Linux Kernel not passing through multicast UDP packets

Recently I've set up a new Ubuntu Server 10.04 and noticed my UDP server is no longer able to see any multicast data sent to the interface, even after joining the multicast group. I've got the exact ...
12
votes
5answers
18k views

Tools to test multicast routing

I am looking for a good simple tool that runs on a standard OS (Windows or Linux) that I can used to test that multicast is being passed properly by a router. I have been asked by a client to enable ...
10
votes
4answers
957 views

How common are dropped packets in communications within a data center?

Let's say I have 2 machines in the same data center but not necessarily in the same rack. How common would dropped packets be when sent using UDP between these two machines? I'm asking under the ...
9
votes
1answer
372 views

Simple Multicast Design

In order to support desktop imaging requirements I need to correct the multicast design on an existing network, but am not well versed in this subject. The diagram below gives a basic example of the ...
7
votes
5answers
776 views

Convey multicast (to another LAN) through WAN disabling multicast

My Server and Client softwares run both on Linux. The Server broadcasts multicast, the Client listens multicast. My Client has to migrate to another site, and unfortunately multicast is not allowed ...
7
votes
4answers
13k views

How can I test Multicast UDP connectivity between two servers?

I have a two servers on the same subnet. I have an application installed which uses Multicast UDP to propagate events between the servers and keep them in sync. This does not seem to be happening, ...
7
votes
1answer
2k views

iperf max udp multicast performance peaking at 10Mbit/s?

I'm trying to test UDP multicast throughput via iperf but it seems like it's not sending more than 10Mbit/s from my dev machine: C:\> iperf -c 224.0.166.111 -u -T 1 -t 100 -i 1 -b 1000000000 ...
6
votes
1answer
2k views

Multicast hostname lookups on OSX

I have a problem with hostname lookups on my OSX computer. According to Apple's HK3473 document it says for v10.6: Host names that contain only one label in addition to local, for example ...
5
votes
5answers
1k views

Is IPv6 multicast routable over the Internet?

As I understand it, public IPv6 addresses allocated by the IANA will have the prefix 2000::/3. These ip addresses will be routable through the Internet. IPv6 multicast addresses on the other side are ...
5
votes
1answer
3k views

Why is pfSense blocking multicast traffic when it is explicitly enabled?

I have a pair of pfSense firewall/routers set up in CARP/XML Config cluster. On the LAN side, the switch also has a pair of servers running corosync/pacemaker/drbd. These are on a different ip ...
5
votes
2answers
3k views

How managed switches handle Broadcast Multicast and Unicast?

Under typical scenarios, a network switch needs to handle broadcast, multicast and unicast messages at the same time. I'd like to understand On a typical managed switch (1Gb Ethernet/10Gb Ethernet), ...
5
votes
1answer
131 views

Why would I ever (really) want to implement dense mode when dealing with PIM routing?

I'm introducing some PIM routing into my network to make some multicast traffic available across routers. I have read a bit on PIM, sparse mode versus dense mode. After reading, I am trying to ...
5
votes
1answer
162 views

ntp multicast address

A silly question probably, but guess I need to ask. If I've got four centos boxes that are acting as ntpd multicast servers, will the multicast address configured in each box's ntp.conf all be the ...
5
votes
4answers
2k views

Capturing multicast data with Wireshark with IGMP Snooping Enabled at the switch

I am trying to capture multicast traffic via Wireshark (actually TShark), however the switch has IGMP snooping enabled and will only send Multicast traffic on the ports that have an active IGMP ...
5
votes
1answer
1k views

windws server 2008 udp multicast performance problem

I encounter a strange performance problem on 2008 R2 Enterprise SP1. Here is the setup: Many processes listening to distinct Multicast UDP streams (5 multicasts listen by process) bound on a single ...
4
votes
5answers
110 views

send files to dozens of servers quickly

We have a cluster of machines (around 50 and growing). Each machine has a search index that needs to be updated multiple times per day. We currently update the index on each machine individually, but ...
4
votes
4answers
3k views

Multicast File Transfers

I'm looking for some multicast file transfer software. Do you have any suggestions? Must be "quickly implementable", i.e. no Tivoli or other stuff that requires a massive infrastructure. Must run on ...
4
votes
1answer
241 views

Current IP Multicast reference materials [closed]

Can anyone recommend a textbook or online resource for learning the current state of multicast technology, from the perspective of a network engineer/designer? The 'bible' that most of my more ...
4
votes
2answers
2k views

Multicast routing across two subnets with FreeBSD 9 (Bonjour between subnets)?

I have a FreeBSD 9 router (a Soekris net6501) connected to the internet via a dsl modem (bridged), doing NAT for two internal subnets, 10.0.1.0/24 (LAN) and 10.0.2.0/24 (wifi net). There are routes ...
4
votes
1answer
169 views

Calculating and billing IP multicast usage on the Internet

I've been searching for the reasons why IP multicast isn't widely supported on the Public Internet, and a commonly-cited reason is the difficulty ISPs have in tracking Multicast usage for later ...
3
votes
11answers
2k views

Most resilient form of (private) DNS clustering?

I'm working on a setup with two datacenters linked by a MAN (bridged) and everything is doubled between them, in fail-over mode with RedHat Cluster, DRBD and that kinf of things. I have one DNS ...
3
votes
4answers
5k views

Why does multicasting make the WAN inaccessible?

I'm hesitant to ask this question as I may not be able to perform the diagnostic steps to find out what is up, but: I need to re-image a lab in a school, possibly during school hours. I am using a ...
3
votes
4answers
673 views

Is there a good way to keep IPv6 multicast packets off WiFi?

I work on a product that consists of a number of headless Linux boxes that work together as a cluster. These boxes synchronize their state with each other by sending proprietary-format link-local IPv6 ...
3
votes
4answers
1k views

Multicast in Rackspace cloud

On Amazon EC2, I cannot use multicast, but how about rackspace cloud? It would be very beneficial to be able to use multicast as most clustering protocols rely on it...
3
votes
1answer
81 views

Streaming root/source in multicasting sparse mode

I'd like to verify if I understand multicasting correctly. In a pim sparse-mode configuration, the RP rtr becomes the "root" of the stream for the rest of the configured routers. Does this mean that ...
3
votes
1answer
1k views

How to monitor a UDP multicast stream on a cisco network, hopefully with SNMP

We have a LAN with 2x Cisco 4500's as gateways running HSRP. We're using Exterity HD IP Encoders to take HD video and put it onto the network as a multicast UDP stream (playable in VLC). I have a ...
3
votes
1answer
49 views

What interaction is required for a Windows server and Cisco router to setup and destroy a Multicast session?

I'm trying to understand how Multicast actually works, and have read numerous articles and Wiki pages, and have gathered this: A multicast address takes up state on the router of the membership, ...
3
votes
1answer
158 views

Should IGMP Snooping be configured on all Layer 2 switches on LAN?

We've used Multicasting for the first time in one of our applications and whilst I have got it working, I'd really like to fully understand how it works and what's going on behind the scenes. In an ...
3
votes
1answer
2k views

Multicast doesn't seem to be working on RHEL 5.5

I'm trying to install Oracle Grid Infrastructure on two machines. Their documentation states: You must enable multicasting for the cluster on the IP address subnet ranges 224.0.0.0/24 and ...
3
votes
1answer
141 views

Server Unresponsive with Spike in Multicast Packets Received

I got a server from UbiquityServers about a week ago, I installed a simple Apache server and it just serves up images. The server is under very little load because it simply is an origin server behind ...
3
votes
2answers
2k views

IGMP/Multicast routing in Linux

I need to route IGMP/Multicast traffic across two networks. I have a Linux box with two NICs, one public, one private. Need devices on the private network to flow to public. I'm pretty certain I ...
3
votes
2answers
184 views

Split multicast traffic on two vlans using IOS

Here is what I want to do: On a switch / router running cisco IOS ( Ideally it would work on a Lanbase image on a 3560G but it is possible to use 65xx routers also ) I receive two udp multicast ...
2
votes
4answers
658 views

Should a small company block multicast on their network?

Currently, the firewall at a small company is blocking multicast on their network. Should they continue to block multicast? Are there security concerns to unblocking it? Are there benefits to ...
2
votes
3answers
1k views

Why are my listener-less multicast packets affecting Wifi performance?

I've got a program that sends out a IPv6 multicast packet (to ff12::2:0:8afb:382b:c053:85f%en1) every 50ms. I've got it running on a very simple single-computer LAN (Mac mini <-wifi-> Linksys wifi ...
2
votes
2answers
406 views

MS NLB: why are multicast packets received by all servers on the LAN, not just members of the cluster

I have a MS NLB cluster (Win 2003) which includes just two hosts. The cluster is configured to use Multicast operation mode (not IGMP). For some reason I am seeing packets intended for the NLB ...
2
votes
2answers
673 views

Can a TCP/IP be efficiently multicast among clients without UDP

I have a high bandwidth application in which a server is to be producing data a rate of ~300Mb/s on a gigabit network. Is there a way other than UDP to multicast to 1 to 10 clients through a reliable ...
2
votes
2answers
367 views

Multicast IP Addresses

I posted this on StackOverflow and was told it might be more appropriate here. I'm having trouble understanding how multicast addresses work. First off, is it true that if I have N clients or peers ...
2
votes
1answer
6k views

How do I know if IP Multicasting is enabled on my network in Windows?

How do I know if IP Multicasting is enabled on my network? It is same question as above but for windows.
2
votes
1answer
988 views

Confusion about HSRP Groups

If I have a router that has several LANs on it, and each of these LAN is attached to a second router, do I need to use different HSRP groups for each LAN? With this set up, each virtual gateway will ...
2
votes
1answer
314 views

Ubuntu 14.04 Ipv6 multicast

I having troubles to setup an IPv6 multicast server with Ubuntu 14.04, the server fails with Invalid argument when try to bind to IPv6 multicast address, checked with mcfirst tool and got the same ...
2
votes
1answer
93 views

How does iptables determine which packets are multicast?

Are packets assumed to be multicast solely based on their ip address? I've been looking at the RFC 1112 and a quick scan doesn't appear to indicate any other flags on the ip packet.
2
votes
2answers
2k views

Multicast over SSH

I have two LANs: 10.x.x.x and 192.x.x.x. On each LAN I have a Linux machine (10.x.x.5 and 192.x.x.5) but they are not routers. I can open ssh from 192.x.x.5 to 10.x.x.5. There are multicast udp ...
2
votes
1answer
3k views

How DNS service discovery, multicast DNS and Bonjour are related?

I am a bit lost in the terminology. I wanted to start to use Bonjour. As the first step, I tried to find an easy way to use it. And I thought that I, probably, can call Bonjour from the command line ...
2
votes
1answer
161 views

Setting up NLB in a VLAN

I have a network layout like this (ESXi hosts): Internal Network + +-----------------+ ...
2
votes
3answers
303 views

Why would IGMP and MLD be required to forward unregistered packets to all ports?

First, a little background: My understanding is that the purpose of IGMP (and its IPv6 cousin, MLD) is to avoid wasted bandwidth by ensuring that multicast packets only get transmitted to ...
2
votes
1answer
139 views

Does the IGMP querier have to be connected to the multicast source?

I've been reading Allied Telesis' guide on configuring IGMP, which has been quite enlightening so far. However, I'm still wondering whether the IGMP querier has to be connected directly to the ...
2
votes
2answers
2k views

Can I test broadcast packets on a single machine?

I want to have a server sending broadcast UDP packets and two other clients, in the same machine, receiving them. Can I do that somehow? What IP address would I use? @gravyface gave me hope but I ...
2
votes
2answers
3k views

multicast tcpdump and subscriptions

From the multicast howto: IP_ADD_MEMBERSHIP. Recall that you need to tell the kernel which multicast groups you are interested in. If no process is interested in a group, packets ...