Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
New Member

Bridging llc between vlans with MSM/s

I have 2 core 6509's with MSM's and 7 of 40 vlans that are bridged only with one MSM for llc traffic. I have 2 hub routers that are the dlsw peers that go to the host that are also in the same bridge group. We are trying to get full redundancy in the network but the customer has had problems before with enabling bridging on the second msm.We are running hsrp on all interfaces. I guess I'm looking for help in spotting the issues. There were several spanning tree problems that have been cleaned up.

thanks in advance


Re: Bridging llc between vlans with MSM/s

Having 2 points of entry from a transparantly bridged domain into a source route bridged domain, ie DLSW, is not supported unless you are running the DLSW Ethernet Redundancy feature - the following URL explains this feature and why -


New Member

Re: Bridging llc between vlans with MSM/s

Cisco's DLSw+ Ethernet Redundancy feature is a solution for remote DLSw+ router redundancy (ie., multiple DLSw+ routers connected on the same LAN/VLAN bridge segment). DLSw+ ER is NOT a recommended best practice redundancy solution for the core campus data center. The reason this is so is because with DLSw+ ER you have to configure static mac address mappings. When doing this for remote DLSw+ routers you only need one entry for the host mac address and a very limited amount of host mac addresses. However if you were to do this on the core data center side you would need to configure one entry for each remote mac address which is not feasible! This URL on DLSw+ ER configuration should give you appreciation for what's involved here:

A much better approach to SNA transport to the host redundancy you might want to investigate is using DLSw+ for SNA transport over the WAN and combining DLSw+ and Cisco's SNA Switching Services (SNASw) APPN IOS feature in central site data center routers. The Enterprise Extender feature of SNASw would allow you to transport SNA traffic from DLSw+ IP to the host (SNA/LLC traffic uses the DLSw+ VDLC connection in the router to get SNA traffic from DLSw+ to SNASw). This results in LLC traffic being transported IP L3 over the MSFCs instead of L2 bridged. Path redundancy for LLC traffic over IP utilizes dynamic IP routing. There is extensive information on this in the SNASw Design Guide on Cisco CCO:

CreatePlease to create content