Getting Broadcast traffic from one 3745 to another

[dturley]

The topology is simple. Three 3550 switches as the backbone tied together using spanning-tree layer 2 wire speed switching. Very simple stuff there. Introduce 3745 access routers, one attached to each 3550, each loaded with 16port ESW, 1 GigE GBic card, and a 8A/S card.

The problem is we have systems that blow out broadcast traffic that needs to traverse accross all 16-ESWs. We have tried all manor of things but we can not get broadcast traffic to traverse the 1GE port. We can see packets hitting the interface but they are simply getting dropped on the floor.

I can go into more detail if needed but we think we're missing a painfully simple detail. Perhaps something to do with L3 and L2? Perhaps something to do with bridge groups or vlans or helper protocols?

Any wisdom to help us out would be greatly appreciated!

[dturley]

Rick,

We had success today with the helper-address!

We cleared out the configurations of the 3745s and configured them with just the broadcast-multicast helper as defined in the earlier posting. Seemed a bit slow to start but we did see broadcast converted to multicast and arrive at the second 3745 router.

It is entirely possible that our previous configuring excersizes were too hasty to allow the routing to converge. Sounds hand-wavy but at this time I will take it.

There is a slight issue yet with the traffic making it back onto the VLAN where the NM-16ESW ports live but the broadcast has traveresed the first and second 1GE L3 interfaces.

To answer your questions:

The UDP port number is abitrary. We chose 5425.

The 1GE interfaces live on the same Class C but are each in there own subnet per each 3745. The IP numbers I gave are not exactly correct.

The 16ESWs are all in a common VLAN. All are in the same subnet.

The 1GE in the 3745 is the uplink to the 3550.

Broadcast sources are on the 16ESW only.

The helper address was configured on the 1GE interface. The destination address was a multicast address, 239.3.5.35.

Anywho, Rick, thanks for your input.

~Dwayne

[lnguye]

A possible solution would be BVI. Please see the link

http://www.cisco.com/en/US/products/hw/switches/ps606/products_configuration_guide_chapter09186a008007d109.html

Regards,