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From: jnd@sms.com (Jose Nabielsky)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: FDDI Dual-Homing SAS Attachments
Message-ID: <29881@boulder.Colorado.EDU>
Date: 16 Nov 90 20:45:52 GMT
Sender: daemon@boulder.Colorado.EDU
Lines: 46



The following is the reply I got from Robert Fletcher at cisco in reference
to my earlier "FDDI Dual-Homing SAS Attachments" message. (cisco has done it
right, again.)

-Jose
 jnd@sms.com

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>> The behavior we *expect* from the dual-homed interface is as follows:
>> 
>> 	1.	The PHY_B interface provides the default attachment to the
>> 		FDDI backbone (through the PRIMARY DAS Concentrator).
>> 
>> 	2.	The PHY_A interface provides a hot standby attachment
>> 		(through the SECONDARY DAS Concentrator).
>> 		
>> 	3.	Upon detecting a hardware- or software-induced PHY_B
>> 		disconnect, PHY_A automatically provides restoral attachment
>> 		(through the SECONDARY DAS Concentrator).
>> 
>> 	4.	When path continuity is restored to the PHY_B interface,
>> 		the router reverts to its default PHY_B attachment.

	We do not give a bias to PHY_B, we go WRAP on the PHY that 
	completes PCM/CMT first. The other PHY will go into "stand-by"
	"sleep" mode.

	If PHY_B completes PCM/CMT first we will insert our MAC as wrap_b.
	If PHY_A completes PCM/CMT first we will insert our MAC as wrap_a.

	If the fiber is disconnect we revert to the secondary PHY (assuming
        it is connected). If the primary is re-connected, we DO NOT break
	the ring to re-install the primary.

	Either of the PHYs can be shutdown via an exec command.

	This works at 8.1(25), will work better at the next maintenance
	release of 8.1, and is incorporated in the next major release 8.2.

Fletcher 
cisco Systems

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