Conference 7.286::fddi

559.0. "Bridge/Concentrator config question" by MADBAS::JHANNAH (Jim Hannah, Telecomms & Networks, AYO) Wed May 06 1992 11:47

Hi,
   Can someone please tell me if the configuration shown below is legal and
will work as I expect? The setup is as follows:-

o 2 DECconcentrators connected to the dual ring

o DECbridge 620's dual homed to the concentrators, so that if one concentrator 
goes down the other is still there connected to the bridge.

o Each DECbridge is connected to the three ethernet segments shown, the second 
bridge being in backup mode.


Am I right in thinking that at power-up, one of the bridges will go into backup
state, but will automatically fail over if the other bridge goes down?


Jim.



Ethernet 1                           ||
     |          DECbridge 620        ||  Dual Ring Backbone
     |          ------             ------
     |----------|    |-------------|    |DEConcentrator 500
     |     /----|____|      /------|____|
     |    /     /    \     /         ||
Enet2    /     /      \   /          ||
     |  /     /        \ /           ||
     | /     /          X            ||
     |/     / 1 ------ / \_________------
     |     /   \|    |/            |    |DEConcentrator 500
     |    /  2--|____|-------------|____|
         /     /     DECbridge 620   ||
Enet3|  /     /      in backup mode  ||
     | /     3                       ||
     |/        Backup connections    ||
     |         to segments           ||
     |

    Looks good to me.  One bridge will go into forwarding on all 4 ports
    and one will go into backup on all but one (connection towards root). 
    If any one port on the "designated" bridge goes down, the related port
    on the backup bridge will go into forwarding (after a delay, I think
    it's 30 seconds)
    
    Note that you would then have a greater latency for traffic between the
    "failover" ethernet and the other ethernets.  I don't think there is
    anything you can do about this other than manually increase the link costs
    on the partially failed bridge to force the backup bridge to take over
    forwarding on all ports.
    
    Steve

Nice configuration...

	paul;