Multicast forwarding

[lvarga]

Hi,

Cat3750 needs to forward multicast between vlans. Multicast address is 224.0.0.251.

I've tried several methods, but it did no succeed. The switch log debug says one of the following :

IP: s=192.168.2.4 (Vlan2), d=224.0.0.251, len 72, stop process pak for forus packet

or

IP: s=192.168.2.4 (Vlan2), d=224.0.0.251, len 72, unroutable

Multicast routing is enabled. I've tried igmp helper and ip multicast helper as well.

Is it possible to forward this Multicast address ?

Regards,

L.

[Georg Pauwen]

Hello,

which PIM mode (sparse,dense,sparse-dense) do you have configured on your VLAN interfaces ? Can you post the configuration of your 3750 ?

Regards,

GP

[Richard Burts]

I believe the problem has less to do with the PIM mode specified and more to do with the address chosen. I quote this from the IANA documentation on assignment of multicast addresses:

The range of addresses between 224.0.0.0 and 224.0.0.255, inclusive,

is reserved for the use of routing protocols and other low-level

topology discovery or maintenance protocols, such as gateway discovery

and group membership reporting. Multicast routers should not forward

any multicast datagram with destination addresses in this range,

regardless of its TTL.

What is generating this multicast traffic and how did it choose this particular multicast address?

I believe that if you change the address to something outside of the reserved range that it will work much better.

HTH

Rick

[lvarga]

Hi,

Application use this address, named : Filemaker. The client use this address to find its the server.

This address can not be modified.

As I know this is a multicast DNS address.

Thank you for help,

L.

[huzhg_8]

you cant use 224.0.0.x for multicast address ,can use other address for it!

best wish!