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Questions tagged [multicast]

For questions about multicast communications and protocols.

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29 votes
1 answer
104k views

What are the benefits and cons of IGMP snooping?

Our new router is asking if we want IGMP snooping enabled. Not being familiar with this, I looked to the internet and got the following wiki description: IGMP snooping is the process of listening ...
1 vote
1 answer
59 views

Should (IPv6) multicast subscribers send report to query?

I am waking through RFC3810 and playing with MLDv2. From that RFC I thought when anyone send query for group :: (all groups) and send it to address ff02::1 all subscribers on segment should send its ...
1 vote
0 answers
152 views

How to forward UDP unicast messages to multiple destinations [closed]

I am trying to forward a UDP Unicast message so that it cant be received by multiple computers. Can anyone point me in the right direction for how to accomplish this? Here are the details: There are ...
1 vote
1 answer
62 views

Can ELI/AAI/SAI addresses be Multicast?

In a slideshow by IEEE regarding the Structured Local Address Plan (SLAP), I saw the following table: SLAP local identifier SLAP Quadrant Z bit Y bit X bit M bit second hex digit ELI 01 1 0 1 0 A ...
0 votes
1 answer
88 views

High latency - dense-sparse mode PIM

Colleagues, good day! In my prod, I notice large delays to some switches behind which there are hosts with multicast reception I wanted to know if my multicast is set up correctly, is it normal that ...
1 vote
1 answer
73 views

Why does a PIM DM assert loser reply with a prune?

In PIM Dense Mode, why does an Assert loser send a Prune message to the winner? What is the actual motivation for this?
0 votes
1 answer
1k views

Can a Bridge forward frames with the destination as broadcast/multicast

I have a question regarding multicast and broadcast frames on a network bridge. Will the bridge forward these frames from one network segment to another network segment ?
1 vote
0 answers
36 views

Should a multicast router punt the multicast packets in addition to routing those packets if the router has an interface in this multicast group?

If the multicast router has the (S,G) route present and the same destination address G is also set on one of the router interfaces, then should the router send the packets addressed to group address G ...
1 vote
0 answers
31 views

What are the triggers for PIM-DM prune and assert messages?

There are articles explaining the PIM-DM mechanics, and they only confused me. Considering the most common topology, that of three routers, connected to each other like a triangle as such: R1 -- R2 \ ...
0 votes
2 answers
59 views

What ways are there to make sure router multicast tables are up to date?

I've been reading on IGMP v3 and think I understand the basics of how to join a multicast group - sending a Membership Report Message. But I'm not sure what the "best" or even conventional (...
0 votes
1 answer
69 views

How does a PIM router know which neighbour is the upstream router?

I understand that certain PIM messages such as Join/Prune and Graft have a field called 'Upstream Neighbour Address' used to indicate the recipient of the message, which is the upstream router for a ...
1 vote
1 answer
37 views

Is there an IGMPv1 querier router after all?

I recently looked into the mechanics of IGMPv1 and v2. Reading RFC 1112, I understand that in IGMPv1, the Querier Router functionality does not exist. All IGMP configured routers in a local network ...
3 votes
2 answers
2k views

Rationale for EXCLUDE mode in mutlicast IGMPv3 / MLDv2

Both IGMPv3 and MLDv2 have an include and an exclude mode, where a multicast listener can specify to either listen only for packets from some list of source addresses (include) or only for packets ...
3 votes
3 answers
1k views

Regarding Multicast over the internet

I was going through the use cases of GRE tunnel and see that it is also used to carry multicast traffic over the internet.I understand that multicast IP belongs to class D address which is a public IP ...
3 votes
2 answers
1k views

Defining what type of casting based on IPv4 address

I'm kinda new to networking. I have a small question, how can I determine what type of casting (unicast, multicast or broadcast) is it based on IPv4 address. For example: 142.55.172.200 I tried to ...
5 votes
2 answers
424 views

What does 'moving packets away from the source' in RPF means?

I recently started studying multicast and I am a bit confused by how reverse path forwarding is explained. Most of the sources describe RPF as 'moving packets away from the source' but I understand ...
1 vote
1 answer
44 views

ipsrc multicast group

I'm looking at some traces where a TTL exceeded in transit ICMP message with ipsrc as mcast is captured. The ICMP message is referencing the original ip header with a correct structure [ipsrc ucast, ...
1 vote
1 answer
327 views

Multicast destination address and port translation (NAT/PAT)

I have a requirement to translate multicast traffic destination address and port number. I see that Cisco has a feature called Multicast service reflection which translates the IP address, but it does ...
0 votes
1 answer
112 views

IPv6-over-IEEE802.15.4 Multicast scope

An IPv6 Multicast address is defined as | 8 | 4 | 4 | 112 bits | +--------+----+----+-------------------------------------+ |11111111|flgs|scop| group ID ...
0 votes
1 answer
94 views

When using multicast, all users have same bandwidth?

I'm reading https://ieeexplore.ieee.org/abstract/document/9370130 and in this paper, achievable rate for the uplink transmission from user n to the UAV is w_n is the bandwidth allocated to user n(...
3 votes
1 answer
92 views

Two multicasts from same source not reaching a destination

I have a single multicast source (Server A) sending to destinations 239.0.0.226 and 239.0.0.227, the source being directly connected to Switch A on VLAN 100. Switch A is sending dozens of multicasts ...
0 votes
2 answers
958 views

UDP supports multicasting and broadcasting in transport layer or application layer?

We know that UDP does supports multicasting and broadcasting. My question is which layer "UDP supports multicasting and broadcasting"? Is it transport layer or application layer? We know ...
1 vote
1 answer
184 views

Ospf multicasting with two different group

Suppose I have one ospf network where two multicast group exists. And some routers is ospf which belongs to one group or multiple group (Like: routers E, H) and router is layer3 router (Like: ...
1 vote
0 answers
92 views

How do I set up IPv6 multicast over an MPLS carrier?

I'm setting up an MPLS carrier with VPNs in GNS3, using Cisco 7200 routers. Exact version I'm using is C7200-ADVIPSERVICESK9-M Version 15.2(4)S5, but I'm willing to upgrade/change if that's needed. On ...
0 votes
3 answers
301 views

PIM Packet and NAT

Is it possible to NAT PIM Join packet? Assume the receiver and the source are in two different networks (address regimes). Thus NAT is required. The upstream source and the groupe are included in the ...
3 votes
1 answer
872 views

IPv6 neighbour discovery blocked by MLD snooping switch

I recently noticed that my IPv6 multicast traffic was being broadcasted to all hosts connected to a switch, even those that had not subscribed to the traffic. To fix this, I enabled MLD snooping on ...
0 votes
1 answer
214 views

Igmp snooping based multicast forwarding

In Igmp snooping switch receives an Igmp leave report? Is it possible to change the timeout value in Igmp snooping switch?
2 votes
1 answer
680 views

If a switch doesn't support multicast, are multicast packets simply flooded out all ports?

If a switch doesn't support multicast, are multicast packets simply flooded out all ports? This would allow multicast enabled hosts to at least still receive the multicast frames. Follow up question. ...
7 votes
2 answers
3k views

How is Multicast IP mapped to Multicast Mac address?

My main concern is why is the address 01-00-5E- and how? Especially 5 and E??
1 vote
1 answer
377 views

broadcast instead of multicast for CARP/VRRP/keepalive

In many cloud environments, multicast is blocked therefore when trying to configure CARP/VRRP customer needs to add a dedicated switch. For example, CARP partially works if using a vSwitch from Hetzer,...
2 votes
3 answers
704 views

Why does OSPF use flooding despite using multicast?

We know that flooding is only possible in layer2 switch. But in OSPF router in layer3 uses flooding with multicasting. Suppose we have one router in OSPF uses multicast address 225.0.0.9. If router ...
6 votes
4 answers
23k views

What are real life examples of broadcast and multicast?

In broadcast routing, packets are sent to all nodes even if they do not want it. What is a real life example of "broadcast"? Almost everything I can think of, like GMail and YouTube, appears to be ...
7 votes
3 answers
9k views

OSPF and its use of Multicast

When it comes to OSPF and its use of multicast, am I correct in believing that IGMP forwarding and an IGMP querier is still required within the local segment? My understanding would be without this, ...
0 votes
2 answers
544 views

Class D network for multicasting between group

We know Multicasting is defined as a single source sending to multiple recipients on a network when the receiver broadcasts a signal for acceptance. Multicasting has its own Class D IP addressing ...
1 vote
1 answer
430 views

IGMP in multiple switches with multiple Senders and Receivers in same VLAN

I am trying to send multicast traffic from 3 Senders to corresponding Receivers in same VLAN (100) spread across 3 switches. I setup a Querier in one of the switch, but it doesn't seem to forward ...
0 votes
1 answer
168 views

What are the benefits of using MP-BGP multicast address family, under the context of inter PIM domains multicasting?

Under the context of inter PIM domains multicasting, 1 RP on each PIM domain (2 domains), attached with eBGP, with MSDP peering to exchange the actives sources, what are the benefits of using the MB-...
1 vote
1 answer
2k views

Forward Avahi mDNS packets from one network to another [closed]

I have a Linux device connected to two different networks. eth0 is connected to 198.18.248.x and wlan0 is connected to 198.19.255.x. Another device connected to the 198.18.248.x network and it's ...
2 votes
0 answers
145 views

No entry in the multicast RIB while PIM join is present

I have a router which receives multicast traffic from the source over a multicast LSP(signaled by LDP): root@PE3> show pim join detail Instance: PIM.master Family: INET R = ...
0 votes
1 answer
144 views

Juniper vMX router silently drops SSM traffic

I have a Juniper vMX router with two interfaces: ge-0/0/0.0 facing the multicast sender and ge-0/0/2.0 facing the multicast receiver. The router receives multicast packets addressed to 232.1.1.1 on ...
2 votes
2 answers
636 views

Query regarding IGMP Querier Election Process

I wanted to understand how a querier election takes place. Say we have to L3 devices with ip address 10.1.1.2 and 10.1.1.1. PIM is not enabled anywhere. I checked around and found that the flow would ...
1 vote
1 answer
101 views

How Pruning avoids loops in Protocol Independent Mulitcast (PIM- SM)?

I can not think of a scenario, how pruning avoid loops in PIM-SM when a router joins a SPT. I understood that it avoids duplicate messages, but how it avoids loops? I want a scenario where the router ...
0 votes
0 answers
111 views

static IP multicast routing with IPSEC

for a specific application, I need to route a multicast flow with IPSEC (we use a CISCO ASA 5508 firewall), I am not a network expert then I will try to explain as best as I can our issue I don't need ...
0 votes
0 answers
90 views

Does multicast over tunnels (e.g., GRE) require IGMP/MLD?

When subscribing to a multicast group on a tunnel device such as a GRE tunnel, are you supposed to participate in IGMP/MLD over that tunnel in order to announce your membership in the multicast group? ...
0 votes
1 answer
1k views

How to Stream from VLC using Multicast? [closed]

I have the following topology: With the following router configurations: R1: hostname R1 ! boot-start-marker boot-end-marker ! ! ! no aaa new-model no ip icmp rate-limit unreachable ! ! ! ! ! ! no ip ...
1 vote
0 answers
422 views

Multicast traffic through Cisco3850

I have a test scenario and trying to pass multicast traffic through Cisco 3850 according to the following diagram: ![enter image description here MC source: several MC IPs such as 232.0.26.0, 232.0.27....
0 votes
1 answer
310 views

What prevents a device from receiving its own multicast stream, and can it be turned off?

I know that it is normally not possible for a device to receive its own multicast stream on the same network interface where it transmitted said stream. I also understand why this is sensible, and ...
7 votes
1 answer
3k views

Why is the NDP Neighbor Solicitation message sent to the solicited-node address?

As I understand it, when Host Alice knows Host Bob's IPv6 address but not its MAC, Alice sends an NDP Neighbor Solicitation (NS) message to the solicited-node multicast address for Bob. Alice knows ...
3 votes
1 answer
10k views

config pimd on Linux to forward incoming multicast packet to OpenVPN tunnel interface [closed]

Does anyone know how could I setup pimd on Linux so that multicast address from 225.0.30.30 could route to 172.24.0.66/30 router on the right? So this is the lab I just setup today, In the lab ...
2 votes
1 answer
326 views

In an IGMP V2 membership report message, isn't the destination Ethernet address based on the multicast group IP address?

Specifically, I think for this message type the Ethernet destination address always starts with 01:00:5E, followed by the second byte of the IP address masked with 0x7F, followed by the third and ...
4 votes
3 answers
8k views

What is the difference between source based tree and shared cost-based tree?

In case of multicast routing, I encountered source based tree and shared cost based tree.What is the difference between source based tree and shared core based tree? In which case they are used? what ...

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