System information

Troubleshooting DECnet
Book Title
11-266
DECnet: Routing Node Adjacencies Toggle Up and Down
Symptom: Routing adjacencies toggle up and down. Output such as the following appears
repeatedly on the DEC system console:
%%%%%%%%%%% OPCOM 30-JUN-1993 1:25:07.45 %%%%%%%%%%%%
Message from user DECNET on The Bay
DECnet event 4.16, adjacency rejected
From NODE 12.1 (The Bay), 30-JUN-1993 1:25:07.45
Circuit UNA-0, Adjacent node = 1.101 (Vax1)
%%%%%%%%%%% OPCOM 30-JUN-1993 1:25:07.46 %%%%%%%%%%%%
Message from user DECNET on The Bay
DECnet event 4.15, adjacency up
From NODE 12.1 (The Bay), 30-JUN-1993 1:25:07.46
Circuit UNA-0, Adjacent node = 1.12 (Vax2)
This output indicates that routers are constantly being added to and removed from the routing table.
The OPCOM messages specify DECnet events 4.16 (adjacency rejected) and 4.15 (adjacency up)
for specific routing nodes.
Table 11-6 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 11-6 DECnet: Routing Node Adjacencies Toggle Up and Down
DECnet: No Phase IV Connectivity over Phase V Backbone
Symptom: Communication between DECnet Phase IV areas separated by an ISO CLNS (Phase V)
backbone fails. Phase IV nodes cannot communicate with other Phase IV nodes across a Phase V
cloud. However, nodes can communicate with one another within the same Phase IV cloud.
Note For more information about troubleshooting DECnet /OSI internetworks, see Chapter 12,
“Troubleshooting ISO CLNS.”
Table 11-7 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 11-7 DECnet: No DECnet Phase IV Connectivity over Phase V Backbone
Possible Problem Solution
Total number of routing nodes on
network segment is more than 32
DECnet limits the number of adjacencies that can be established by a router
to 32.
Step 1 Enable the debug decnet events privileged exec command to
determine whether the adjacency is being rejected. Enable this
command on one router at a time.
Step 2 If the adjacency is being rejected, reduce the number of adjacent
routers on the segment.
Hardware problem Check the error message output to identify the routing node or nodes that are
causing the adjacency to toggle.
Follow the procedures outlined in Chapter 3, “Troubleshooting Hardware and
Booting Problems.”