During an emergency maintainence window on Saturday morning 10/24 at 05:00 EST we isolated the routing software problem to what we believe is a bug that will cause the routing software to fail if the T3 backbone maintains active peer sessions (EGP or BGP) with more than 85 AS systems. We believe this is the cause of the routing instabilities that occured on Tuesday evening 10/19 and Friday morning 10/23. The bug in the rcp_routed software involves the MIB interface code. This problem has been reproduced on the T3 testnetwork. A new version of the rcp_routed software has been generated and tested on the testnet. This version is now running on two unused nodes on the T3 production network. Because the number of AS's peering with the backbone can vary dynamically, we plan to install this bug fix on the production T3 system during an emergency software maintainence window on Sunday morning 10/25 between 05:00-08:00 EST to avoid any further instabilities. The release notes for this new rcp_routed are available via anonymous FTP from ftp.ans.net in the file /pub/info/t3-rcp_routed/Release-Notes Jordan Becker, ANS NSFNET/ANSNET Network Operations