Conference 7.286::fddi

670.0. " Enabling LAT on FDDI and Ethernet Interfaces" by SANFAN::RICHARDS_LA () Mon Aug 10 1992 23:27

Hi there,

We currently have an FDDI backbone which is bridged to our extended Ethernet
via a couple of DECbridge 500s (no filtering is enabled).  We have two
4000 model 60s which are connected to the FDDI and Ethernet.  I enabled 
LAT on both interfaces and created a single service, but I'm confused 
as to how all this works since the multicast LAT advertisements from the 
FDDI and Ethernet interfaces will pass through the bridges.  When I 
first created the links in LATCP it gave both links the same datalink 
address.  I then decided to use the /NODECNET qualifier on the Ethernet 
link since we were only running DECnet on the FDDI.  This resulted in 
the Ethernet link getting the hardware address and the FDDI link getting 
the DEC physical address.  It sort of works...

Meaning we can connect to the 4000 via LAT, but which interface you 
connect to is a bit of a mystery.  It appears, from monitoring a 
terminal server on the Ethernet that the address for the 4000 actually 
changes from the AA-00-04 address to the 08-00-2b periodically.  I 
contacted Colorado about enabling LAT on both the Ethernet and FDDI
interfaces and they did NOT tell me that this was an unsupported 
configuration, but from reading the notes files I get the feeling that 
maybe this isn't supported.

If enabling LAT on both the Ethernet and FDDI on a single extended LAN 
is not supported can you please explain why (I think I know) and can you 
tell me where this is documented?  

What I was hoping to do was somehow set the preferred path to the FDDI 
interface and then if FDDI failed to automatically fail over to the 
Ethernet interface.  Do you know of any dynamic way to accomplish this 
if it is not doable by enabling LAT on both interfaces?

Thanks in advance for your help.  I also posted this note in the LAT
     
conference.

Laurie Richards
                                   

You can only run LAT on one of the interfaces.  Otherwise the terminals servers
will get upset that the address of the node is constantly changing.