steve@calvin.vf.ge.com (Steve Cunningham) (05/11/91)
May 9, 1991 General Electric Aerospace network 1000 Macintosh, 40 routers ( ethernet to local talk) I am involved in the effort to break this large bridged network up into 11 sub-nets. We have cisco routers on order (11 IGS and 15 AGS+). We are conducting a demo with Cisco's help and we learned quite a bit about Appletalk Phase II and Cisco routing. We quickly learned of the two well known problems : MCI boards don't talk to each other unless fast caching off note: this is fixed in a later beta firmware Random, somewhat transient AARP failures casusing some zones to float in and out. note : also fixed in later beta ware But last week we stumbled onto a new one which was a surprise to all, but even now, Dave Edwards has built a fix and distributed (via internet). The problem is that a cisco ethernet port can confuse itself with a node which has the same node address, although a different network or cable address. eg: cisco port E0 has address 4. a node ( we had three) had address 4656.48 also legal. The cisco acted as if he were that node. Symptom, any node with a xxxx.48 could not see anything on the other side of the AGS+ any port. Since all of our apples need to acess a mainframe on port 1 these nodes were "broken" After some furious protocol analysis we realized that packets (NBP) were passed from the node through the cisco heading for the named service. Fine. The return packets with address 4656.48 would go into the cisco and not come out. The cisco thought it was that node and did not forward the packet. We had three nodes with .48 addresses. By zapping P-RAM we fixed one machine by making him take a non .48 address. Strong evidence. Then, we wrote a quick little code whichallowed the reading and writing of that entry in P-RAM where the hint for the address is stored. Re boot the Mac and you have created a xxxx.48 machine. It then showed as "broken". Cause and effect ! Last thursday 2 May we reported this to cisco. New code ready on Friday which we downloaded. Booted the AGS+ via tftp and problem solved. All .48 machines returned to service. Conversations with Dave Edwards and Patrick Jones assure us that this fix will be included in the 8.3.(4) release which is due out officially in one or two weeks. Hope this adventure is of use to others; for more info I would be happy to talk. Steve Cunningham 215-354-4906 General Electric P.O. Box 8555 blg 19 Philadelphia, PA 19101 Looking forward to sharing other cisco adventures. steve