We have a multicast source that sends out 4 streams. When I go to the recieving router and run the command below it get a high number of multicast drop. My video would play for about 5 minutes than hang. Is this drop related to my video hanging? What is the best way to troubleshoot this problem? Thanks
A26-LAN-R1#show ip mroute 22.214.171.124 10.20.32.109 count
IP Multicast Statistics
270 routes using 501884 bytes of memory
24 groups, 10.25 average sources per group
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)
I don't have any rate-limit any of the configured items you mention. However, I'm a little confused about the packet forwarding and packet recieving.
If that output was from an SVI, where the multicast source (10.20.32.109) was connected to, then should I have more packet forwarding and less receiving. Also, if multicast is udp, why am i getting recieved at all. Sorry, since new to multicasting.
no problems all of us are here to learn and share.
from the point of view of the multilayer switch SVI:
packets are received from the source via the multicast tree.
eventually they are forwarded out
the show is not specific of an interface it focuses on a multicast group and provides statistics for it.
Another important basic question is the type of IP multicast routing you have configured and achieved:
there are PIM sparse mode
PIM dense mode
in any case to have a multicast stream to be successfully forwarded from Vlan X to Vlan Y you need to enable ip pim on source vlan, destination vlan and if there routers in the middle in all transit links on the path from vlan x to vlan y
The basic difference between PIM dense mode and PIM sparse mode is:
PIM sparse mode requires explicit join to add an interface to the list of interfaces for a group (that is the OILIST)
PIM dense mode will forward the packets out of all multicast capable interfaces: downstream devices can signal they are not interested on the stream with an explicit Prune message for the group.
The pruned state is timed with a timer that can be of few minutes: after that the group is flooded again and if a new prune is received again forwarding stops.
so PIM DM uses a flood and prune method while PIM SM waits for an explicit join.
How have you configured multicast in your network ?
another aspect are parallel paths to the source.
If there are paralled paths to the source with equal unicast routing cost this can be a problem because RPF will choice only one interface as the one in which it expects to receive traffic from the source and if packets arrive on the other are dropped with cause RPF failure
This is not your case as I commented in my first post
To see what type of PIM is in use
show ip mroute multicast-group-address
to see Rendevous point mapping if any
show ip pim rp mapping
if you like you can post the output of these shows here.
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