Think of multicast and unicast as two different routing infrastructures configured on the same physical network. Whenever a packet has a unicast destination IP address, routers will deal with that packet using the regular routing tables that have been created from static routes and dynamically learned routes from routing protocols.
If a packet has a multicast destination IP address, then routers will use the configured multicast routing table, which as been created using featurs such as IGMP and PIM.
So both unicast and multicast routing capabilities coexist on the same network, and therefore, based on the specific application, it is possible to transmit Layer 4 and Application layer protocols such as those you mention, using either unicast or multicast.
My question is about Sparse mode, You must give a RP (static, auto or BSR) but i donāt understand the difference between RP and Mapping agent. Can you Help me ?
thanks
Arlette
In sparse mode, you do need an RP. If you configure the RP manually, then you donāt need a mapping agent. However, the mapping agent comes into play when you enable a process called Auto-RP, which is a Cisco proprietary method of automatically choosing an RP for a multicast topology.
In the Auto-RP process, there are two roles that multicast routers will play: Candidate RP, and Mapping Agent. As Rene states:
The candidate RP is a router that announces itself that it wants to be an RP for the network. It does so by sending RP announcement packets to the 224.0.1.39 multicast address.
The mapping agent listens to the RP announcement packets from our RP candidates and makes a list of all possible RPs. It will then elect an RP and informs the rest of the network with RP mapping packets that are sent to multicast address 224.0.1.40.
This is taken from the following lesson:
You can find out more about these roles and how they operate by reviewing this lesson, which describes this process in detail.
Hi
Thanks for your help.
Others question : is there possible to have the solution about this https://gns3vault.com/multicast/multicast-advanced. Maybe have you the con of the router for this lab (multicast avanced )
Thank
You said IGMP is a protocol that hosts use to tell the router that they want to receive specific multicast address traffic. So, IGMP is enabled by default on Routers ? We havenāt to configure anything on them ?
IGMP is indeed a protocol that is used by hosts to inform routers they want to receive traffic from particular multicast groups. You can see how IGMP can be configured on routers by taking a look at the following lessons:
Typically, you should use version 3, but Iāve linked to all versions for your reference. By default, IGMP v2 is enabled on a PIM-enabled interface of a multicast router.
So I am doing a core upgrade and IGMP snooping is disabled globally on the old core, but the old core has IP CGMP configured on some of the SVIs. Since IP CGMP isnāt available on our 6880 core switch should I enable IGMP on the new core? Also is IGMP snooping needed in a layer three switch network?
Although CGMP is a protocol that will achieve what you need as far as IGMP snooping is concerned, it is best practice to use the IGMP snooping feature rather than CGMP. If your equipment supports IGMP snooping, it is preferrable to enable it throughout your network rather than using CGMP.
Remember IGMP snooping is used to to restrain multicast traffic in a Layer 2 switched network. By default, a Layer 2 switch floods multicast traffic within the broadcast domain, and this can consume a lot of bandwidth if many multicast servers are sending streams to the segment. With IGMP snooping, multicast traffic is restricted to ports connected to multicast receivers only.
For more information on IGMP snooping, take a look at the following lesson:
It depends on what you mean when you use the term āinteractiveā. The term āinteractive multicastā is typically used for the type of multicast that allows the automatic joining and leaving of receivers from multicast groups. The implementation of multicast in an IP environment is indeed interactive in this sense because using IGMP, hosts can join and leave multicast groups.
If we look at multicast more broadly, we can see that it exists in other telecom infrastructures as well, such as in cellular data, packet radio, and even in conventional voice telephony. Some of these are not considered interactive multicast because they may not dynamically create multicast groups, but may only operate statically.
So to answer your question specifically, yes, multicast that is implemented in an IP environment is indeed interactive.
I tested The below configuration on Cisco 3825 router NAT is working fine for both unicast and multicast traffic. But when I tested on Cisco ISR 4321, NAT is only working fine for unicast traffic, multicast only working with original source IP.
ip nat pool pool-108 137.1.1.1 137.1.1.1 prefix-length 30
ip nat pool pool-118 192.100.46.11 192.100.46.11 prefix-length 30
ip nat inside source route-map MAP-108 pool pool-108
ip nat inside source route-map MAP-118 pool pool-118
access-list 108 permit ip 192.168.1.0 0.0.0.255 172.1.1.0 0.0.0.255
access-list 108 permit ip host 192.168.1.1 host 224.1.1.1
access-list 118 permit ip 192.168.1.0 0.0.0.255 192.100.46.0 0.0.0.7
access-list 118 permit ip host 192.168.1.1 host 225.1.1.1
route-map MAP-108 permit 10
match ip address 108
route-map MAP-118 permit 10
match ip address 118
Please help me to suggest how can I make this config working on cisco ISR 4321.
Thanks.