muticast and unicast

[bluesea2010]

Hi,

What are the pros and cons for running multicast routing  and unicast routing  on the  same  core swites and access layer
Thanks 

[Jon Marshall]

Not really sure what you are asking here. 

PIM which is the default multicast routing relies on the unicast routing table anyway so you would run them together if you need to enable multicast in your access layer. 

So if you want multicast it's not really a question of whether you run them together or not, you need to. 

Jon

[bluesea2010]

Hi @Jon Marshall 

Usually people are doing layer2 multicast instead of l3 , What is the reason behind this 

That was my point

Thanks 

[Jon Marshall]

Again not clear what you are asking. 

If you need multicast within a vlan then L2 is fine but if you want multicast between vlans you need L3 multicast routing. 

What you do depends on what you need. 

Jon

[Joseph W. Doherty]

The biggest pro, running unicast and multicast on the same devices, you only need to use one device for both, and as Jon notes, when using something like PIM multicast, you need the unicast route tables.

The biggest pro, running unicast and multicast on different devices, if "something" runs amock, in either the unicast or multicast environment, there's a better chance that the other environment might not be impacted at all, or not as much.

You also ask about the possibility of splitting unicast and multicast even at the access layer, unsure how you would make this work unless your hosts were dual homed.

BTW, you might also consider, if you have dual devices for core and distribution layers, you might "prioritize" unicast and multicast such that each "prefers" a different device than used by the other, while "backstopping" each other.