It's my first time configuring multicast on a switch. Do I need to configure both Layer 3 and Layer 2 for multicast on a single VLAN that is in DHCP? Should I enable IP multicast routing on Layer 3 and PIM sparse-mode on that VLAN? Also, do I need to enable IGMP snooping on Layer 2?
I was wrong they do not have IGMP snooping enabled by default.
WTH?
Your reference does say IGMP snooping isn't enabled by default, but I too recalled it was enabled by default. Mind you, my memory is sometimes faulty, but did some Cisco digging and found:
Configuring IGMP Snooping Globally
Perform this task to modify the global configuration for IGMP snooping.
Before you begin
IGMP snooping must be enabled. IGMP snooping is enabled by default.
By default, IGMP snooping is globally enabled on the switch. When globally enabled or disabled, it is also enabled or disabled in all existing VLAN interfaces. IGMP snooping is by default enabled on all VLANs, but can be enabled and disabled on a per-VLAN basis.
So, it's possible the default varies between platforms or IOSs, the latter default different, maybe, especially, if IPv6 MLD is supported.(?)
So, best advise would now be determine if IGMP snooping is enabled or not.
BTW, if disabled, multicast should work fine, just multicast will be sent to ports where it's not desired.
If IGMP snooping (or MLD) is working correctly, only those ports wanting a particular multicast stream should obtain it, but if working incorrectly, multicast might be blocked to ports that desire it. (If the default enablement has changed, possibly another reason to have the default being disabled would be to preclude operational multicast issues.)
I mean on Catalyst 1300 IGMP snooping is not enabed by default, not on every enterprise level switch ( where it is enabled by default)
Ah, gotcha.
However, IGMP snooping might also be desired on the mentioned core 9500 depending on logical topology, where it likely is enable by default.
Again, @dianawinsky if you have multiple switches supporting a VLAN with multicast snooping, you'll want an active querier, either implicitly via a router PIM interface or switch configured as a querier.
I appreciate your inputs on my post. After configuring multicast in L3 without configuring the access switch since you guys said that IGMP snooping is globally enabled on the switch, how can I test if it's working?
in your access switch in advance mode Multicast > IGMP/MLD Snooping IP Multicast Group.
You can see some multicast groups bound to the switch ports. When a client requests multicast traffic, the related port should bind to the multicast group. This way, you can check whether the entire multicast configuration works or not.
