[Search for users] [Overall Top Noters] [List of all Conferences] [Download this site]

Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

2361.0. "DEChub 900 IP Services from DECbridge 900MX, other bridges, switches a bad idea?" by CRONIC::LEMONS (And we thank you for your support.) Fri Jun 09 1995 14:05

Hi

The HUBwatch V4.0 Release Notes state, in 7.4.3:

	"Be cautious when using the DECbridge 900MX to provide IP
	 services for the hub.  If the bridge is in learning mode
	 when it receives SNMP requests from HUBwatch, the requests
	 may be lost and HUBwatch may encounter SNMP timeouts
	 without any real indication of the problem to the user.
	 Because of these timeouts the HUBwatch windows that made the
	 requests may be corrupted."

We're using a DECbridge 900MX to provide IP services to a DEChub 900, and we are
seeing intermittent SNMP failures.  Is this problem expected in just the
DECbridge 900MX, or in any bridge or switch (for instance, the DECswitch 900EF)?

Thanks!
tl
T.RTitleUserPersonal
Name
DateLines
2361.1This is *not* a problem, it is a normal behavior...NETCAD::BATTERSBYFri Jun 09 1995 15:3618
    First be careful when using the word "problem". This *not* a problem.
    It is a normal mode for a bridge/switch to be in a learning state
    or pre-forwarding state prior to entering the forwarding state.
    Any Digital bridge/switch (that I know of), will have a pre-forwarding
    state before entering the forwarding state. This pre-forwarding
    state lasts 30 seconds. After the bridge/switch goes into the
    forwarding state, there should be normal management dialog that
    will occur between a host making SNMP requests and the bridge/switch.
    This holds true for the DECswitch 900EF (which is nothing more than
    the current version of a DECbridge 900MX with a new bezel). So if you
    are doing warm resets/restarts to the DECswitch 900EF (or to your
    DECbridge 900MX), you have to wait until the switch/bridge is back into 
    the forwarding state.
    The release note is simply advising the user of the normal behavior
    of a bridge and to take this into account before conversing with it
    via SNMP requests.
    
    Bob
2361.2CRONIC::LEMONSAnd we thank you for your support.Fri Jun 09 1995 15:535
Thanks for the clarification, and pardon my ignorance!  So 'learning mode' is a
state a bridge is in ONLY when it is powered on or reset?

Thanks
tl
2361.3Learning is a continual function of a bridge...NETCAD::BATTERSBYFri Jun 09 1995 17:4611
    Not quite correct. During the preforwarding state, a bridge port is
    receiving frames and learning the source addresses of these frames 
    and building its address table. Then it enters the forwarding state 
    where it continually receives and forwards frames to/from addresses 
    that it learns, and continues to receive and forward frames from 
    previously learned addresses.
    So a store and forward bridge is always "learning" addresses. There are
    many sources of information which go into details of this process, like
    the Bridge and Extended LAN reference.
    
    Bob
2361.4NETCAD::DOODYMichael DoodyFri Jun 09 1995 18:395
    And it will go into pre-forwarding or learning any time you make a
    connection change, like plugging a cable into a port.
    
    
    md
2361.5CRONIC::LEMONSAnd we thank you for your support.Fri Jun 09 1995 18:565
Okay.  But considering a steady state of no new cabling to the bridge, should
the learning that continually take place negatively impact the bridge's ability
to provide IP services to the Management Agent Module?

tl
2361.6NETCAD::DOODYMichael DoodyFri Jun 09 1995 20:1412
    No, normal forwarding operations of a bridge are not supposed to
    affect the management of the bridge or the MAM when its used for IP
    services. It is when the port that is used for communication between
    Hubwatch and the MAM is in pre-forwarding state that you see the
    timeouts - when the port is pre-forwarding, no communication takes
    place. It should last 30 seconds and then you're done.
    
    If you're seeing timeouts during management of your Hub and the bridge
    is steady-state (you're not changing the configuration of your bridge
    or anything connected to the bridge) then there is a problem. 
    
    md
2361.7NETCAD::ANILWed Jun 21 1995 16:255
    Re .0: The quote from the HUBwatch release notes is misleading, and
    the earlier responses correctly answer your questions.  I'll talk
    to the doc. people on getting this clarified.
    
    Anil