IPV4 MULTICASTING OVERVIEW & IGMP

IPV4 MULTICAST ADDRESSING
-------------------------
IPV4 multicast use "CLASS D" addressing
224.0.0.0/4 (224.0.0.0-239.255.255.255)
This includes reserved ranges
Link local address
  224.0.0.0/24  (224.0.0.0-224.0.0.255) alot of protocols use like ospf = 224.0.0.5 eigrp  
224.0.0.10
Source Specfic Multicast
  - 232.0.0.0.0/8 (232.0.0.0-232.255.255.255)
Administratively scoped
  -239.0.0.0/8 (239.0.0.0-239.255.255.255)

Multicast COntrol Plane
------------------------
Multicast control plane is used to determine
  - who is sending traffic and to what groups
  - who is recieving traffic and for what groups
  - how traffic should be forwarded when it recieved
  - The multicast "tree"
The control plane is built with a combination of
  - host to router communication (IGMP)
  - ROuter to Router communication (PIM and MSDP)
Once the tree from sender to revciever is built the traffic begins to flow
Before forwarding Dataplane checks occur
  - Reverse Path Forwarding (rpf) check
     - was traffic recieved on expected interface??
  - Multicast routing table (Source based)  
     -what interface should i forward the packets out

Control Plane=IGMP
-------------------
Internet Group Management Protocol
  used for reciever (end host) to signal to router on the lan
Enabled automatically when pim is enabled
  - ip pim [dense-mode|sparsemode|sparse-dense-mode|passive
- IOS runs IGMPv2 by default
    ip igmp version [1|2|3]
You configure PIM Passive when you have 1 router servicing the LAN. In general only 1 router
should forward traffic directly on single segemnet as anything else is duplicate. The modes
of pim spare/dense will decide which router on the segment is nominated to do this if there
is multiple routers. Where you configure a router as passive your statically defining that
this is the only router servicing the segment do it does not check so if you config multiple
routers as passive you could have duplicate on the segment
IGMP MEMBERSHIP
----------------
IGMP hosts signal membership to router via Report
   - IGMP v1/v2 supports only group specification *,G report
   - IGMPV3 support group & source specific  joins (S,G)
Router can iniate join with
    ip igmp join-group "groupaddress" [source "source-address"]
   
     ip igmp static-group * "group-address" source "source-address|ssm-map
*,G is basically you just want the traffic from that group you do not casre where it came          from it could be multiple source as long as it going to that group
S,G you want the traffic from a group but it also has to be originated by particular source

IGMP CONVERGENCE
-----------------
How often to check for active membership (how often you ask the host are you still listening)
ip igmp query-interval
how long to watit for a query response before implicit leave is assumed
ip igmp query-max-response-time

how long before deciding that querier is gone
ip igmp querier-timeout
how many queries after explicit leave is heard before group is pruned (in igmp v2 + v3 when the host leave it sends a explicit leave message)
ip igmp last-member-query-count
how ofter a query is send after recieving a explicit leave (this is query asking is anyone else listening on the segment after explicit leave is recieved)
ip igmp last-member-query-interval
if explicit leave,prune without sending query
ip igmp immediate-leave
track eacch ssm recieved not just (S,G) in this it will keep track of all reciever node not just source + group. So say a group source may have 5 reciever it keep track of these individual if it recieves 5 leave message it knows that the group can be pruned

MISCELLANOUS IGMP FEATURES
---------------------------
Filtering
    - control what groups can be joined
        ip igmp access-group
    - control how many groups can be joined
       ip igmp limit
    -stub multicasting routing
      send all reports and leave upstream
       ip igmp helper-address