Date: October 28, 1998

During the course of the Network 21 Stage 3 cutover process, various issues and problems have been encountered and resolved. In an effort to proactively avoid difficulties during future projects, the Network 21 team has collected a list of these issues for public access.

1. NAM Adds/Changes/Deletes At Cutover
2. Length of Cutover
3. Use of Department Hubs
4. Network 21 Outage Notifications
5. MAC Address Registration and Expiration
6. Reserved IP Addresses
7. Windows NT Server Issues
8. Unix Hosts
9. Printers

If you have any questions about this document or would like to suggest items to add to this list, please contact the Network 21 team via e-mail at net21helpdesk@ucdavis.edu.

1. NAM Adds/Changes/Deletes At Cutover

Early on in the Network 21 cutover process, it became apparent that last minute NAM additions, changes and deletions were going to be the rule rather than the exception. During the first series of department cutovers, the Network 21 crews received various requests to alter the list of NAMs scheduled for cutover. A process was quickly developed and was used effectively throughout the remainder of the cutover schedule to accommodate these last minute changes. It is recommended that any future network migration efforts implement a similar formal process.

2. Length of Cutover

On many occasions, department technical contacts had expectations that contradicted published Network 21 policy with regard to the length of the cutover, and consequently, the downtime associated with the cutover. Some department contacts thought that each PC or host would be cutover one at a time, and downtime would be limited to a few minutes. Other department contacts expected the entire cutover process to take 20 to 60 minutes. While the vast majority of department contacts understood the published information regarding the cutover process, some miscommunication occurred, causing a small number of departments to have unrealistic expectations for the cutover process and associated downtime. Future efforts should make every effort to disseminate policy information on the cutover process and set realistic expectations for downtime.

3. Use of Department Hubs

Various policy statements regarding the use of fan-out devices are available on the Network 21 homepage at net21.ucdavis.edu. In general, Network 21 policy limits the number of connected hosts/nodes to 20 or less per fan-out device. However, as the default settings on the Network 21 switches are optimized for a single host connection, any use of a fan-out device on Network 21 creates some potential for connectivity problems. To minimize these potential connectivity problems, Network 21 personnel examined the port statistics on switches that had completed cutover. If fan-out devices were detected on a particular switch port, the port default settings were adjusted for optimized performance with fan-out devices.

4. Network 21 Outage Notifications

Network outage notifications have been issued upon occasion to provide downtime for code upgrades and preventative maintenance actions on various Network21 devices. In future network migration efforts, it would be extremely beneficial to institute a weekly or bi-weekly network maintenance/downtime window to perform code upgrades or tune network parameters as necessary.

5. MAC Address Registration and Expiration

MAC addresses remain registered on Network21 switches for a minimum duration of 30 minutes. This can result in an apparent network failure during relocation of a network device. For example , a user with a laptop computer connected to a Network21 switch (Switch A) disconnects from her office NAM and takes her laptop to another room. She plugs into another NAM, which is connected to a different Network 21 switch (Switch B). After 2 or 3 minutes, LAN Emulation ARP (LE-ARP) entries on Network 21 ATM equipment will timeout and most network services will be available to the laptop via its new network connection. However, there will be problems with network connectivity between the laptop and any devices connected to its original Network 21 switch (Switch A). These problems are the result of the 30-minute MAC address registration on the Network 21 switches. Switch A still considers the laptop to be connected to it for up to 30 minutes after the laptop has been disconnected and moved. After 30 minutes of inactivity, the MAC address on Switch A is unregistered, and all network connectivity issues are resolved.

6. Reserved IP Addresses

Network 21 reserves the last 3 host addresses in all subnet ranges. These addresses are used for the default gateway, a potential secondary gateway and an address for test equipment. This address reservation scheme is different than the reserved address space on the legacy UCDNet and generated some slight confusion among the user community.

7. Windows NT Server Issues

In the Windows NT environment, the order that servers are cutover is important. The primary domain controller and DHCP server (if used) should be cutover first. This facilitates synchronization when secondary servers are cutover. Print servers and network printers should be cutover before client workstations. Otherwise, clients will have to re-login after the network printers are cutover.

8. Unix Hosts

Most of the connectivity problems experienced by Unix hosts during the Network 21 cutover were the result of an incorrect network mask configuration. Network 21 help desk personnel were briefed on this issue in order to provide assistance to department technical contacts.

9. Printers

Some difficulties were experienced with HP printers during the cutover process. In general, the network problems were corrected by resetting the printer configuration to the factory defaults before re-configuring new network address information.