Conference 7.286::fddi

1313.0. "Chipcom dual homing problems" by VNABRW::KOISSER () Mon Apr 11 1994 12:45

    Hi there !                                        
    
    I 've a situation that i hope anybody can help.
    A customer of mine has 6 Chipcom 5017 Hubs and 2 DECconcentrator 500
    that formed a dual Ring.
    23 DECbridges are dual homed on the Chipcom Hubs only.
    
    
    Example:
    
              --------     dual Ring   --------          -------
              CHIP1   ================  CHIP2    =======  CHIP3
              --------                 --------          -------
                      \                /
                       \              /
    			\A          B/
                        -------------
                        DECbridge 620
                        _____________
    
                 
    Configuration on the Chipcom Hubs:
    
    	Slot 1-2  5000M-RCTL    Fault Tolerant Contr. Module  V002
        Slot 4    5032M-MGT1    FDDI Management Module        V1.10
    	Slot 6-10 5308M-FIB-ST  FDDI Fiber Module             V2.00
    
    
    Using DECmcc V1.3 and privat MIB "CHIPMIB02"
    
    I get very often SNMP TRAPs = "LINK DOWN" messages on the passiv 
    link genereted from "all" the Chipcom Modules 5308M whitch are
    connected to the A Ports of the DECbridges.
    After that a second Trap without any Status or "Link up" information 
    occurs from that Link.
    
    The active Path works fine at this time.
    LWL Cables are checked und no other major hardware fault was found yet.
    
    1) Do you think this might be a problem with the LCT
       Extendet Link Confidence Test --> every 50 sec. on the Bridges?
    
    2) Or a missmatch - FDDI ANSI X3T9.5 Standard between DEC and Chipcom? 
    
    
               any urgent help welcome !
    
                                        Best regards, 
                                           Heinz K.
    
    
    
    
    
    

It sounds like Chipcom is not handling correctly the way dual homing is defined
to operate.

In dual homing, the backup link (A port link) runs a 50 second link test, then
restarts, does another 50 second link test, restarts, ...  It does not at any
time go to "link up" state.  This is what the SMT standard requires.

The right way to handle this is to report nothing.  It's a mistake to send
a "link down" message every 50 seconds, since the link wasn't up to begin with.

	paul

    thanks Mr. FDDI
                       Heinz