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9 votes

OSPF and its use of Multicast

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 ...
Ron Maupin's user avatar
  • 99.8k
7 votes
Accepted

Multicast between VLANs

VLANs logically break a switch into multiple, unconnected switches. There is no traffic between VLANs (layer-2), except through a router (layer-3). By default, routers do not route multicast packets. ...
Ron Maupin's user avatar
  • 99.8k
5 votes
Accepted

KEMP load balancers using UCARP (VRRP) - multicast MAC address not being picked up

I was able to resolve the issue. On the Kemp (with HA pair) you have the option of using a "Virtual MAC Address". If this box isn't checked, then the MAC of a load balancer VIP is that of the physical ...
Ed Smith's user avatar
5 votes

Multicast between VLANs

There is no inter-VLAN communication without a router. Multicasts are not usually routed - unless your router is specifically configured to do so.
Zac67's user avatar
  • 84.8k
4 votes

Multicast routing on Huawei Quidway 5300 Switches

It’s been a while since I used VLC, but when you set up the server end, check to make sure that the TTL of your stream isn’t set to 1 (which used to be the default), otherwise the stream will never ...
Benjamin Dale's user avatar
4 votes
Accepted

IGMP snooping across VLANs

Switches with multiple VLANs look like multiple switches, and they maintain separate tables for each VLAN. For example, a switch with two VLANs will have two MAC address tables, one for each VLAN. ...
Ron Maupin's user avatar
  • 99.8k
4 votes

How do you disable IGMP-snooping on virtual nic macvtap

This is actually a known issue and there are a couple of ways to fix it. The best one is actually to edit the XML definition for the libvirt network and add trustGuestRxFilters=yes to the ...
rnxrx's user avatar
  • 6,114
4 votes
Accepted

OSPF and its use of Multicast

In terms of what happens to OSPF hello/discovery multicast packets, you're right. The switches send them to everyone on the subnet/VLAN/broadcast domain, as IGMP snooping isn't happening for 224.0.0.0/...
Marc 'netztier' Luethi's user avatar
3 votes
Accepted

How can MLDv2 work according to the RFCs 3810 and 4606?

1. If not, what does compatibility mode version 1 mean then? According to Mr. Rolland Vida, the author of RFC 3810, with routers/hosts MUST operate in version 1 compatibility mode is meant, that hosts/...
goulashsoup's user avatar
3 votes

IGMP leave group

It depends. If your switching infrastructure is IGMP-aware (IGMP snooping), the IGMP leave group is translated to an Ethernet multicast leave group and that causes the switch port to disable ...
Zac67's user avatar
  • 84.8k
3 votes

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? OSPF's use of multicast is to a link-...
Ricky's user avatar
  • 32.2k
3 votes
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Multicast timer expires

Normally the router will periodically send a membership query to destination 224.0.0.1 (all hosts multicast group address). Hosts that receive this message will respond with a IGMP membership report ...
Viktor Borisov's user avatar
3 votes

IGMP and Multicast

How IGMP specifically works depends on the IGMP version in use. Cisco has some documents related to how the different IGMP versions work in general and specifically on Cisco devices. For instance, IP ...
Ron Maupin's user avatar
  • 99.8k
3 votes
Accepted

Question Regarding IGMPv3 behaviour: Multicast Router appears to send Membership Report?

From RFC3376 The Internet Group Management Protocol (IGMP) is used by IPv4 systems (hosts and routers) to report their IP multicast group memberships to any neighboring multicast routers. Note ...
DRP's user avatar
  • 1,491
3 votes

Rationale for EXCLUDE mode in mutlicast IGMPv3 / MLDv2

The generic answer to your question would be "exclude mode is to be used when the list of IPs you want to listen to is longer then the list of IPs you do not want to listen to". The most common use ...
Gerben's user avatar
  • 4,690
3 votes

Multicast routing on Huawei Quidway 5300 Switches

225.1.1.1 is reserved by IANA so quite possibly the 5300 filters this cast. You should try using an address from one of the ad-hoc blocks 224.0.2.0 - 224.0.255.255, 224.3.0.0-224.4.255.255, or 233....
Zac67's user avatar
  • 84.8k
3 votes
Accepted

Trying to understand IGMPv3 Max Response Code algorithm

I think the part you misunderstood in RFC 3376 Section 4.1.1 that you quoted: Max Resp Time = (mant | 0x10) << (exp + 3) I think it could be clearer (not mixing binary and hexadecimal), but as ...
Ron Maupin's user avatar
  • 99.8k
3 votes
Accepted

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

For IEEE 802, including Ethernet, multicast is realized as a filtered broadcast. Both use a group address with the address's I/G bit set to 1. A broadcast is relayed to every active port (IEEE 802.3 ...
Zac67's user avatar
  • 84.8k
3 votes
Accepted

PIM-SM over OSPF for mDNS traffic

mDNS uses a link-local multicast address (224.0.0.251) that cannot be sent off-link, so you cannot route mDNS packets. RFC 5771: 4. Local Network Control Block (224.0.0/24) Addresses in the Local ...
Ron Maupin's user avatar
  • 99.8k
2 votes

IGMP and multicast forwarding

Routers do not forward multicast unless you have explicitly enabled multicast routing. That requires something like PIM. IGMP is a link-local protocol. Multicast is a form of broadcast, and you ...
Ron Maupin's user avatar
  • 99.8k
2 votes
Accepted

Should igmp table lookup misses flood to all ports?

RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches, Section 2.1.2. Data Forwarding Rules places that decision squarely on ...
Ron Maupin's user avatar
  • 99.8k
2 votes

IGMP Multicast router overrun

Quoting 'cpt_fink': You need something acting as the multicast querier, but not the multicast router. I do not know if this is possible on a TP-Link device. – cpt_fink Feb 18 '15 at 5:19 A ...
Multicast user's user avatar
2 votes

Multiple VLANs under one subnet (for traffic control)

Switches have no concept of subnets. The term is virtual LAN's, VLANs. The management interface on each switch certainly can be on the same VLAN (and subnet). The ring topology requires some flavor ...
Ronnie Royston's user avatar
2 votes
Accepted

Unable to route multicast from IPcam (four vlans, one switch, one router with router-on-a-stick)

Multicast, like broadcast, is normally confined to a single VLAN. To overcome this, there is multicast routing, which is very different than your normal unicast routing. IGMP is only part of that. ...
Ron Maupin's user avatar
  • 99.8k
2 votes
Accepted

Understanding IP multicast in linux

How can we create a Multicast group? A multicast group is not "created". A multicast group is formed of all computers listening to a certain multicast address. Therefore a multicast group ...
Martin Rosenau's user avatar
2 votes
Accepted

Using IGMP but Multicast still Flooding

You need to configure the 2530 for IGMP forwarding, otherwise it'll simply flood. For instance, vlan 1 ip igmp turns on IGMP forwarding for VLAN 1 and sets the switch querier to automatic mode. ...
Zac67's user avatar
  • 84.8k
2 votes
Accepted

Multicast in one VLAN

I should receive traffic if inbetween Juniper IPTV and Qtech 2800 Client there is no igmp snooping configured. You would have to make absolutely sure that this (igmp snooping disabled) is the true ...
Marc 'netztier' Luethi's user avatar
2 votes

How to enable Inter-VLAN multicast traffic on a layer 3 Siemens RX1510 Network Switch using IGMP?

You'll likely want to look into something like Protocol Independent Multicast (PIM), which seems to be covered for that platform here. As Ron points out, IGMP is only managing multicast groups within ...
rnxrx's user avatar
  • 6,114

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