07-20-2009 11:20 AM - edited 03-06-2019 06:51 AM
Hi,
I'd like to enable multicast on a small environment consisting of two 3750 and couple of 2960. Will just enabling "ip multicast-routing" and "ip pim sparse-dense-mode" on all the VLAN that need multicast do the trick? The source address is local to the subnet so are its receivers.
regards,
07-20-2009 11:22 AM
That it would, had the same requirement a while ago.
07-20-2009 11:34 AM
Thanks Rob for the quick reply. I will give this a try on Thursday.
07-20-2009 12:02 PM
Etienne
Also configure igmp snooping on your switches otherwise multicast packets are just broadcast.
Jon
07-20-2009 12:13 PM
If I rememember correctly, since you multicast source and receivers are on the same segment, you might not need to enable multicast-routing, although I believe the interface PIM is needed to activated IGMP query. Even for that, if switches not doing IGMP snooping, multicast should be seen by all hosts on multicast source segment.
Also, if you enable some form of dense mode, and since you haven't defined a RP, you might end up flooding other subnets with multicast until it's pruned.
I.e.
If there no's IGMP snooping, multicast should "naturally" work for source and receivers on same subnet.
If IGMP snooping is active, you'll need a IGMP querier, but shouldn't need multicast routing (again for multicast source and receivers on same subnet).
Lastly, once you activate multicast routing, dense mode will flood and prune other subnets which can be precluded by using sparse mode.
07-21-2009 04:48 AM
Hi Joseph,
It appears that IGMP snooping is enabled by default (see below). If I get your point, if IGMP snooping is enabled, I will have to enable ip pim-dense-mode to enable igmp querier. Is that right?
Global IGMP Snooping configuration:
-------------------------------------------
IGMP snooping : Enabled
IGMPv3 snooping (minimal) : Enabled
Report suppression : Enabled
TCN solicit query : Disabled
TCN flood query count : 2
Robustness variable : 2
Last member query count : 2
Last member query interval : 1000
Vlan 1:
--------
IGMP snooping : Enabled
IGMPv2 immediate leave : Disabled
Multicast router learning mode : pim-dvmrp
CGMP interoperability mode : IGMP_ONLY
Robustness variable : 2
Last member query count : 2
Last member query interval : 1000
Vlan 10:
--------
IGMP snooping : Enabled
IGMPv2 immediate leave : Disabled
Multicast router learning mode : pim-dvmrp
CGMP interoperability mode : IGMP_ONLY
Robustness variable : 2
Last member query count : 2
Last member query interval : 1000
07-21-2009 04:55 AM
Specifically PIM-DM, no, but I recall a configuration of PIM on the interface is what activates the IGMP querier. (BTW, some switches can do this too [i.e. be the querier].)
07-21-2009 04:59 AM
Etienne
"If I get your point, if IGMP snooping is enabled, I will have to enable ip pim-dense-mode to enable igmp querier. Is that right? "
Not necessarily. You do need something to query so that IGMP snooping can listen to the answer. However some switches are capable of being the IGMP querier themselves without having to enable pim on the L3 interfaces. If you do not need to pass multicast traffic across L3 boundaries have a look at the IGMP querier function -
2960 -
3750 -
Jon
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide