multicast issue in a VLAN in Catalyst 3750

Unanswered Question
Mar 27th, 2008

Hi,

How do i enable multicast traffic into a VLANs from other VLANs ?

I have configured point-to-point routed links between 2 catslyst 3750 switches.

(multicast source)VLAN 10 ----Routed link-----> VLAN 11 (multicast destination)

I have enable:

ip multicast-routing distributed

My VLAN interface config is as follows:

Switch A

interface Vlan10

ip address 10.41.10.254 255.255.255.0

no ip redirects

ip pim sparse-dense-mode

no ip route-cache cef

no ip route-cache

no ip mroute-cache

Switch B

interface Vlan11

ip address 10.41.11.254 255.255.255.0

no ip redirects

ip pim sparse-dense-mode

no ip route-cache cef

no ip route-cache

no ip mroute-cache

Is it workable ?

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Harold Ritter Thu, 03/27/2008 - 07:49

I would rather configure "ip pim sparse-mode" on the two vlans and then configure the 3750 as the RP. Otherwise, the multicast data could be flooded to vlan11 even if there is no one interested to this traffic on this vlan.

Regards,

melwongpl Thu, 03/27/2008 - 08:00

Thanks for the reply.

In fact to make it clearer, there will always be multicast traffic in both of these VLANs.

I have tried it out in my lab, but i am unable to receive any multicast. What could be an issue ?

What does no ip mroute-cache meant ?

frederic.lemair... Mon, 11/23/2009 - 11:55

you have to put the pim configuration ( ip pim sparse-dense-mode or ip pim sparse) on the 2 side's L3 interface between your 2 3750.

you should so have something like these on your first 3750 :

int vlan xxx

ip pim sparse-dense-mode

int gi1/0/1 --> L3 to second 3750

ip address 172.16.18.1 255.255.255.0 for exemple

ip pim sparse-dense-mode

and on the second 3750

int vlan yyyy

ip pim sparse-dense-mode

int gi1/0/1 (L3 to first 3750)

ip address 172.16.18.2 255.255.255.0 for exemple

ip pim sparse-dense-mode

if you want to use sparse mode, you need to configure RP ( auto-rp or manual RP).

Regards.

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