If a Layer Two switch doesn't have the capabilities to run IGMP Snooping, it will be able to run CGMP - Cisco Group Membership Protocol. CGMP allows the multicast router to work with the Layer Two switch to eliminate unnecessary multicast forwarding.
Laptop Battery CGMP will be enabled on both the multicast router and the switch, but the router's going to do all the work. The router will be sending Join and Leave messages to the switch as needed. PIM must be running on the router interface facing the switch before enabling CGMP, as you can see:
Cisco Systems, Inc., is the largest manufacturer of networking systems in the world. It dominates the router and switch market to the extent that Cisco routers and switches are considered by many networking professionals to set the standard for all other companies. Cisco routers, switches, and other equipment keep running without problems, are readily upgraded, are easily adapted to new network configurations, and are compatible with virtually every transport or access method.
Thinkpad R1(config)#int e0
It' - the included Setup Wizard takes you through configuring the Router, step by step. The Router can act as a DHCP server for your network, so your PCs are configured automatically. Play (UPnP) lets specialized Internet applications configure the Router so you don't have to. in NAT technology helps keep intruders out of your computers.
Microsoft R1(config-if)#ip cgmp
Occasionally, during your CCNA and CCNP studies, you'll run into a term that just doesn't quite make sense to you. (Okay, more than occasionally!) One such term is "reverse telnet". As a Cisco certification candidate, you know that telnet is simply a protocol that allows you to remotely connect to a networking device such as a router or switch. But what is "reverse telnet", CCNP home lab setup
Laptop Computers WARNING: CGMP requires PIM enabled on interface
- Your computers are in an internal network behind a NAT based router. Only the router has a public IP address. You can access your internal network computers via the Internet. To do this you need to configure 'Forwarding' firewall. Configure the router to forward connections from a port on the router to a specific IP address and port (Radmin server's default port is 4899) of the target computer in your internal network. You need to assign a port on the router for every computer you need to access. The router will then forward the connection to your computer in the internal network.
- Your PCs have real IP addresses but the firewall has its port 4899 closed. In this case you have to open 4899 or use another open port.
- Radmin Server does not start on the server. Examine the log file on the server for the reason.
Laptop Computer R1(config-if)#ip pim sparse
It' - the included Setup Wizard takes you through configuring the Router, step by step. The Router can act as a DHCP server for your network, so your PCs are configured automatically. Play (UPnP) lets specialized Internet applications configure the Router so you don't have to. in NAT technology helps keep intruders out of your computers.
Desktop Computer R1(config-if)#ip cgmp
Notebooks
When CGMP is first enabled on both the multicast router and switch, the router will send a CGMP Join message, informing the switch that a multicast router is now connected to it. This particular CGMP Join will contain a Group Destination Address (GDA) of 0000.0000.0000 and the MAC address of the sending interface. The GDA is used to identify the multicast group, so when this is set to all zeroes, the switch knows this is an introductory CGMP Join, letting the switch know that the multicast router is online.
Lenovo The switch makes an entry in its MAC table that this router can be found off the port that the CGMP Join came in on. The router will send a CGMP Join to the switch every minute to serve as a keepalive.
Hard Drive A workstation connected to the switch on port 0/5 now wishes to join multicast group 225.1.1.1. The Join message is sent to the multicast router, but first it will pass through the switch. The switch will do what you'd expect it to do - read the source MAC address and make an entry for it in the MAC address table as being off port fast 0/5 if there's not an entry already there. (Don't forget that the MAC address table is also referred to as the CAM table or the bridging table.)
Travelstar
The router will then receive the Join request, and send a CGMP Join back to the switch. This CGMP Join will contain both the multicast group's MAC address and the requesting host's MAC address. Now the switch knows about the multicast group 225.1.1.1 and that a member of that group is found off port fast 0/5. In the future, when the switch receives frames destined for that multicast group, the switch will not flood the frame as it would an unknown multicast. Instead, the switch will forward a copy of the frame to each port that it knows leads to a member of the multicast group.
Gateway
Two major benefits of CGMP are the explicit Join and Leave Group messages. In the next part of this BCMSN exam tutorial, we'll take a look at the Leave Group messages.
Laptop Parts
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