A switch running IGMP snooping examines every multicast data packet to determine if it contains any pertinent IGMP control information. If IGMP snooping is implemented on a low end switch with a slow CPU this could have a severe performance impact when data is transmitted at high rates.
No. If you recall, IGMP uses IP Protocol Type 2. Switches with specialized ASICs (to support IGMP Snooping) can simply recognize the IP Protocol Type to distinguish IGMP packets (Type 2) from actual multicast packets that use TCP (Type 6) or UDP (Type 17). As a result, only IGMP packets get snooped.
One of the inherent difficulties in implementing IGMP Snooping is that IGMP Membership Reports are transmitted to the destination IP address of the multicast group that the host wants to join. As a result, IGMP Membership Report packets and actual multicast packets (that use TCP or UDP) are indistinguishable at Layer 2 for a given multicast group since both packets use the same destination MAC address. Had the original designers of IGMP used the "All Hosts" IP multicast address (184.108.40.206), IGMP Snooping would be much easier to implement in software without undue stress to the switch CPU, since all IGMP Membership Reports would use a destination MAC address of 01-00-5e-00-00-01.
If a host IGMP membership report did use the 220.127.116.11 GDA, IGMP would not have to snoop all multicast packets. Is that correct? as the L2 forwarding table would just forward these packet with the mac of 01-00-5e-00-00-01 to the switching engine, or is that nonsense?
As discussed the switch can easily distinguish between M/cast control traffic and data flow. Here i show the Cat6k handles IGMP:
Only the 1st IGMP report per VLAN and per IP multicast group is forwarded to the router.
Subsequent reports for the same VLAN and group are suppressed.
The switch processor creates one entry per VLAN in the Layer 2 forwarding table for each MAC group from which it receives an IGMP join request then hosts interested in this multicast traffic send join (AKA Reports) requests and are added to the port list of this forwarding table entry.
We have 3 identical switches configured by someone else and would like to claim some of the Gigabit ports(G1/G2/G3/G4) for use on servers. When we try to change the wiring and configuration, we run in to connectivity issues. Attached is a des...
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...