21

You cannot multicast on the public Internet, but you can multicast across the public Internet to another site by using a tunnel that supports multicast. Multicast routing is very different from unicast routing, and all the routers in the path of the multicast packets need to have multicast routing configured.


15

IGMP Snooping is a feature for switches to learn what multicast groups are needed on which ports. Routers not handling multicast routing don't care. That said, without an mrouter in the network, you need to configure one (or more) igmp queriers. This ensures group membership reports are flood through the network periodically to keep the forwarding ...


15

Because 224.0.0.0/24 is the range assigned by IANA for local multicast - Local Network Control Block. Addresses in this range are non-routable, they can only exist on a link, and cannot be forwarded by a router. These protocols only require multicast to operate within a single link, often to provide dynamic neighbour discovery and flooding of protocol ...


12

You don't configure multicast address anywhere. Some box sends traffic out with multicast destination, this will automatically get L2 multicast address on the link. This L2 multicast address is normally broadcasted in L2, unless there are some specific features enabled, like IGMP snooping to stop the flooding. If IGMP snooping is enabled, then the L2 ...


12

Well the first difference would be that switchport block unicast blocks unknown unicast and storm-control multicast blocks multicast packets. The difference between switchport block XXXcast and storm-control XXXcast is exactly what you want to exclude in your question. You can pick any percent value for storm-control. It will block traffic of the specified ...


11

The reason that it doesn't have to leave the LAN is that IGMP (or MLD if you use IPv6) only talks to the multicast router on the LAN. The multicast router will take care of the routing.


11

In a word: NO Multicast is a one-to-many system. TCP requires a one-to-one handshake to synchronize counters (sequence numbers) to ensure reliable transport. This cannot be done with many receivers as the sender has no way to know how many receivers there are and thus how many ACKs to expect, or what to do if one of the receivers disappears mid-transfer, ...


11

You can't use any addresses from 224.0.0.0 (except for multicast) through 255.255.255.254, and 255.255.255.255 is a Limited Broadcast address. Multicast addresses are 224.0.0.0/4. Masks are not used in multicast; you subscribe, individually, to multicast groups. Reserved addresses are 240.0.0.0/4. While named "Class E" in the old class routing scheme, ...


10

As an end-user, you cannot multicast across the Internet, unless using a tunnel. As a larger organization, like a video provider or an ISP, it is certainly possible to forward multicast packets across their domain boundary (i.e. across an Internet). How ? Essentially, to forward multicast packets within your own domain (or Autonomous System, AS), you use ...


9

Lets test this out then. If we send multicast packets to multiple devices connected to a WiFi access point at a constant rate, then the access point should report the same amount of traffic. To run this test, I'm sending packets from a wired PC to an an android tablet and a raspberry pi. Don't have any iOS devices. The network testing tool iperf can easily ...


9

As I understand Wifi, it can never true multicast, as each device holds a '1:1" relationship with the AP, and then receives the same packet... then the next device connects and gets the same packet. Your understanding is flawed. Multicast does exist, but like most management traffic on a wireless network it must run at the lowest supported base/basic/...


9

The benefit of multicast is that hosts not subscribing to the multicast group ignore frames they receive that are sent to the multicast group. With broadcast, they cannot ignore the frames. The OSPF multicast group is a link-local multicast that gets sent to every switch interface, even with IGMP snooping enabled on the switch. OSPF only uses multicast on ...


8

As the firewalls aren't part of a vPC they won't be part of the normal vPC loop prevention. The loop prevention only states that a packet cannot ingress on the peer link if it is destined to go out another vPC enabled port. Not too sure on the multicast front as we don't use it in our environment and I haven't really looked into its behaviour on the 7K's. ...


8

I had this problem using multicast with iperf myself - in my case it was due to the fact that iperf does not let you bind to a multicast source on a specific interface and instead just hardcodes itself to the first interface of the system, meaning that, if the response isn't being received on what is typically eth0, it's useless. From what you say, it sounds ...


8

Outside of Karl's explanation, it's a holdover from the original class-based IP addressing scheme. As you know, the classes were as follows (based on the first octet): Class A (0xxxxxxx): [0-127].0.0.0/8 Class B (10xxxxxx): [128.0-191.255].0.0/16 Class C (110xxxxx): [192.0.0-223.255.255].0/24 Class D (1110xxxx): 224.0.0.0-239.255.255.255 Class E (1111xxxx): ...


7

GOOSE uses VLAN and priority tagging as per IEEE 802.1Q to have separate virtual network within the same physical network and sets appropriate message priority level. -- wikipedia That would suggest this traffic is actually within a VLAN. So even if it is broadcast (or multicast), it's only going to go where that VLAN goes. tcpdump has a rather annoying ...


7

Background I am somewhere that blocks Dropbox downloads, so I can't see the captured traffic, but I'll go on the assumption these were 64-byte ethernet multicasts. Let's do some math to see how much traffic you're permitting... A 64-byte frame is 672 bits (including 8 bytes for Preamble/SFD, and 12 bytes for IFG)... 8*(8 + 12 + 64) = 672 bits That means ...


7

PIM messages are not sourced from HSRP VIP's so the RPF check fails since the HSRP VIP is your RPF neighbor. There are two ways around this though. Set up a dynamic routing protocol between your router and the other sides routers so HSRP is not needed. Configure static mroutes to the other sides actual interface IP's such as: ip mroute 0.0.0.0 0.0.0.0 1....


7

I've kept digging around the internet....and I think I've answered my own question. Now I need to go back to the application/device owners/developers and see what we can do or further lock these devices down to their own VLAN. Please leave comments or answers with any further advice. RFC 4541 2.1.2: 1) Packets with a destination IP address outside 224.0.0....


7

Key to answering your question is making a very important distinction: Duplicate Address Detection (DAD) and Multicast Listener Discovery (MLD) are completely separate protocols. Now, that said, I think this paragraph of RFC2710 explains the "duplicate" transmission: When a node starts listening to a multicast address on an interface, it should ...


7

Switches without MLD or IGMP snooping will treat multicast and broadcast (if there were broadcast in IPv6) the same -- namely, they would flood the packets out all ports. But the second half of your statement, "and therefore negate the benefits of multicast" doesn't follow. The advantages of multicast are not for the switch. They are for the end ...


7

Both Reverse Path Forwarding and Unicast Reverse path Forwarding do basically the same thing: Verify that the data is coming from the same direction you would expect it to come from. Their function is slightly different though: 'Normal' RPF will check the source of multicast traffic, to avoid network loops. uRPF will check the source of unicast traffic, to ...


7

MBGP or Multiprotocol BGP extensions The first BGP specification was published in 1989, well before IPv6 was created and only shortly after multicast was added to IPv4. Even BGP-4 doesn’t support IPv6, multicast or VPNs. Until 1998, that is, when RFC 2283 introduced the multiprotocol extensions. These allow BGP to handle routing information for arbitrary "...


7

Can communication to broadcast 224.0.0.1 be made to reach hosts outside of the local subnet? First, that is a multicast group, not a broadcast address. Next, the multicast address is in the Local Network Control Block (224.0.0.0/24), and multicasts sent to groups in that block are limited to the network on which they originate. So given the above ...


6

You need a router. The HP 2520G is a Layer 2 managed switch, and has no Layer 3 capabilities. This is highlighted in the features tab on hp.com and in the 2520G feature support matrix If you're not able to get funding for a router, maybe you could power up a Vyatta VM at the ProCurve site?


6

"broadcast" was replaced with more specific multicast methods. All-station-broadcast would become a huge mess given the available size of IPv6 LANs -- imagine thousands of nodes broadcasting ARPs looking for each other. (it falls apart in IPv4 already) Multicast Neighbor Discovery limits who hears the requests and answers, in a network with multicast aware ...


6

There is another caveat: Depending on platform, the switch will punt all link-local multicast to the CPU. This includes for example OSPF traffic. I noticed this on Ciscos Catalyst 4500 which will send all 224.0.0.x traffic to the CPU. When the CPU is busy it will drop the packets, including your OSPF packets. Have fun debugging why your OSPF session(s) drop....


6

Yes, it's possible. But you would have to advertise a /24 network (or larger), based on current Internet routing policies. So if your name server IP was 1.2.3.4, you would have to advertise 1.2.3.0/24 from each of your locations. The rest of the addresses in that subnet would be, practically speaking, wasted. You also would have to have your own provider-...


6

My questions are: Should we setup on our core network switch OSPF with a router ID of 1.1.1.1 and then not set any OSPF settings on any other switch? OSPF is not necessary for this implementation. Would PIM Sparse Mode only need to be enabled on the core switches or on all of the switches in the network? Pim-SM needs to be enabled on each L3 ...


6

So first of all show fabric utilization all shows fabric utilization, not CPU utilization. Fabric doesn't have CPU component per se, and you can go all up to 100% of fabric utilization without any adverse effects similar to what CPU causes when nearing to the full load. Next, the WS-X6548-GE-TX is 8Gbit/s card, so "old" fabric attached LC with 8Gbit/s ...


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