Conference netcad::hub_mgnt

2960.0. "IMB config cause packet loop !?" by TKTVFS::KOBAYASHI_S (Seiki Kobayashi, Network support/JAPAN) Mon Nov 06 1995 23:55

I have experienced a packet loop when I configured two decswitches on dechub900
using IMB. Is it a spec?

I configured two decswitch on dechub900 by the following step. 

			DS900EF(1)	DS900EF(2)
                        2|  |3          2|  |3
	IMB ethernet_1 --+--|------------+--|----
                            |               |
	IMB ethernet_2 -----+---------------+----

1) Ethernet port 2&3 configured to backplane on both DS900EF. After listening
and learning times, status of both ports(2&3) became forwarding. 

2) I connected port 2&3 of DS900EF(1) to IMB ethernet_1&2.

3) I connected port 2 of DS900EF(2) to IMB ethernet_1 and I connected port 3
to IMB ethernet_2 then packet loop happen about 1 sec.

I think that if I configure the switch port to backplane side then the status  
of the port becomes "Forwarding". So that 2 DECswitch connects to 
same 2 ethernet then packet loop is happen until the specific ports receive 
hello message and change the status to "Backup". This loop time is 
very short(less than 1 sec), however when the worst comes to cause hang-up 
some NIC cards of PC.

Regards,
Seiki Kobayashi