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Multicast (view source)

Revision as of 16:18, 15 December 2022

20 bytes added ,  1 year ago
→‎Sparse-dense-mode
 
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* Host on LAN signal the router to join the multicast group.
 
* Two kind of request
* Two kind of request - (*,G)-Any source who is generating the multicast stream for that group -Supported by IGMP V1 and V2
(S*,G) -want toAny joinsource particularwho sourceis sendinggenerating the multicast stream for that group . -IGMP versionSupported 3by supportIGMP both (s, gV1 and (*,G)V2
(S,G) - want to join particular source sending the multicast group - IGMP version 3 support both (S, G and (*,G)
 
* IGMP get enabled when the IP PIM [Dense mode, Sparse mode, Sparse-DENSE-mode] is enabled.
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* By default IGMP version 2 is enabled.
 
* IP IGMP join group address can be used for testing on routers to see weather multicast traffic is received on router for particular group.
 
* ''ip igmp static group'' command can beCommand used to manually put the request for particular multicast group instead of relying on IGMP query message for particular group.:
ip igmp static group
 
= PIM =
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* Sparse mode uses both source based trees and shortest path trees
* RP needs to know the receivers and senders.
* DR on lan segment send (S,G) register mess age to and RP in turns reply register stop process and receivers on lanLAN segment send IGMP join and which will be converted to pim join(*,G) message to RP to form RPT tree.
* So pim join will traverse from receiver till RP every device will have (*,G) entry and from source till RP every device will have (S,G) entry.
* Once RP knows about sender and receiver it will send (S,G) join request back to source and source would start sending the multicast traffic to RP then to receiver.
* Then its up to the last hop router on receiver side for the optimation process weather it want to join directly to source using SPT bypassing RP.
 
* Note - When we do debug only process switched traffic is debug if we want to debug the data plane traffic then we need to disable cef (no ip route cache),if we change the unicast routing it will also change the multicasting routing, To change the unicast routing we can also use Ip mroute command .
 
 
* Source based tree - tree is build based on shortest path from receiver till sender.
* Shared tree - tree from sender to RP and then RP till receiver.
 
* To check RP configured on each transient router - sh ip pim rp mapping :
sh ip pim rp mapping
* RP can be assigned statically (ip pim rp address) or dynamically (auto RP and BSR)
 
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* 224.0.1.40 - chooses the RP and advertised to rest of routers for RP information.
 
* To stay on shared tree rather than SPT (ip pm spt-threshold infinity)
ip pm spt-threshold infinity
 
== Sparse-dense-mode ==
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* Once the multicast routing table is populated router always prefer (S,G) over (*,G) and in multicast routing table we have incoming interfaces and OIL for outgoing interface list if the RPF check passes multicast traffic is send across all interfaces in OIL.
 
* On multicast router -below sh ip igmp group --command shows which multicast group is active on ethernet and which receiver has joined the group :
sh ip igmp group
 
* To determine which router is IGMP queried router - sh ip igmp interface EO:
sh ip igmp interface EO
 
* We can manually tune the query interval and query max response time - :
* ip igmp query interval -120 ip igmp query interval 120 (default 60 sec) -> query interval
* response time - ip igmp query-max-response-time 20 (default 10 sec) -> response time
 
* IOS command to supportspecify which version of IGMP is -to ipbe igmp version 1/2enabled:
ip igmp version 1/2
 
* Test commands for IGMP
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