Troubleshooting DECnet

Table 9-2 outlines the problems that might cause this symptom and describes solutions to those problems.

Table 9-2 : DECnet: Connections to DEC Hosts Fail over Router (Router Problem)

Possible Problem	Solution
DECnet is not enabled on router	Step 1 Use the show decnet interface privileged EXEC command to see on which interfaces, if any, DECnet is enabled. Step 2 If the output shows that DECnet is not enabled, use the show running-config privileged EXEC command to view the router configuration. Determine whether DECnet global and interface command specifications are configured on the router. Step 3 Enable DECnet routing on the appropriate routers and interfaces. For detailed information on configuring DECnet, refer to the Cisco IOS Network Protocols Configuration Guide, Part 2.
Missing decnet cost command	Step 1 Make sure that there is a cost configured on DECnet interfaces. Check the configuration for a decnet cost cost-value interface configuration command entry. Step 2 If the command is not present, add the decnet cost command for each interface on which DECnet is enabled.
End nodes and router area number mismatch	Step 1 Check the configuration of end nodes and routers on the network segment. Check the area address specified on end nodes and routers. Step 2 If an end node is not in the same area as a router on the segment, you must either change the address of the end node to be the same as a router on the segment, or you must reconfigure a router on the segment with the same area number as the end node.
Actual cost to the destination area is more than the configured cost	Step 1 Use the show decnet interface EXEC command to determine the configured maximum cost to the destination area. Step 2 Use the show decnet route EXEC command to determine the actual cost to the destination area. Step 3 If the actual cost is more than the configured maximum cost, increase the maximum cost configured on the router. On Level 1 routers, use the decnet max-cost global configuration command to increase the area maximum cost. On Level 2 routers, use the decnet area-max-cost global configuration command to increase the area maximum cost.
Actual number of hops to the destination is more than the configured maximum number of hops	Step 1 Use the show decnet interface command to determine the maximum number of hops allowed for intra-area routing. Step 2 Use the show decnet route EXEC command to determine the actual number of hops to the destination as shown in the DECnet routing table. Step 3 If the actual number of hops is more than the configured maximum allowed hops, increase the maximum hops configured on the router. On Level 1 routers, use the decnet max-hops global configuration command to increase the maximum hops. On Level 2 routers, use the decnet areamaxhops global configuration command to increase the maximum number of hops.
Access list is misconfigured	Step 1 Use the show decnet access-list privileged EXEC command to determine whether there are DECnet access lists configured on the router. Step 2 If there are access lists applied to router interfaces, use the debug decnet connects privileged EXEC command to determine whether important packets are being forwarded properly. Step 3 If packets are being dropped, disable all access lists on the router using the no decnet access-group interface configuration command. Step 4 Determine whether connections to hosts are now possible. If connections are made successfully, a misconfigured access list is probably the problem. Step 5 Enable access lists on the router using the decnet access-group interface configuration command. Enable the lists one at a time until connectivity is lost, at which point you have found the problem access list. Step 6 Modify the access list as necessary. Make sure to include explicit permit statements for traffic that you want to be forwarded normally. Step 7 If problems persist, continue the process until you have isolated all problem access lists.
Node address out of range	Step 1 Use the show running-config privileged EXEC command to view router configurations. Check to see if the decnet max-address global configuration command has been configured. This command sets the highest DECnet node number allowed in the area. Note: The decnet max-address command specifies the highest node number allowed in an area, not the maximum number of node addresses allowed in an area. For example, if you configure the command decnet max-address 1000 on a router and you configure a node with a node address of 1001, the address is out of range. Step 2 The default maximum address is 1023. However, if another value is configured, the node address might be more than the configured value. If this is the case, increase the maximum address value using the decnet max-address command.
Partitioned area	Make sure the network topology has no discontiguous areas. If any discontiguous areas exist, reconfigure the topology by changing area addresses or by creating a path (with a router) to create a contiguous network.
Media problem	For information on troubleshooting serial lines, refer to the "Troubleshooting Serial Line Problems" chapter. For information on troubleshooting LAN media, refer to the "Troubleshooting LAN Media Problems" chapter.

End Nodes Cannot Find Designated Router

Symptom: End nodes cannot find a designated router. End nodes cannot access nodes that are on different LANs, but other nodes connected to the same LAN are accessible.

Table 9-3 outlines the problems that might cause this symptom and describes solutions to those problems.

Table 9-3 : DECnet: End Nodes Cannot Find Designated Router

Possible Problem	Solution
DECnet not enabled on router	Step 1 Use the show running-config privileged EXEC command to view the router configuration. Determine whether DECnet global configuration and interface command specifications are configured on the router. Step 2 Enable DECnet routing on the appropriate routers and interfaces. For detailed information on configuring DECnet, refer to the Cisco IOS Network Protocols Configuration Guide, Part 2.
End nodes and router area number mismatch	Step 1 Check the configuration of end nodes and routers on the network segment. Check the area address specified on end nodes and routers. Step 2 If an end node is not in the same area as a router on the segment, you must either change the address of the end node to be the same as a router on the segment, or you must reconfigure a router on the segment with the same area number as the end node.
Hello packets are not being exchanged	Step 1 Use the debug decnet adj privileged EXEC command to determine whether the router is sending hello packets and whether hellos are being received. Step 2 If no exchange is occurring, use the show interfaces EXEC command to determine whether the interface input and output queues are full. A full input queue is indicated by a value of 75/75, and a full output queue is indicated by a value of 40/40. Step 3 If the queues are full and no hello packets are being exchanged, contact your technical support representative. Step 4 If routers are sending hello packets, check end nodes to determine why end nodes are rejecting hello packets.
Media problem	For information on troubleshooting serial lines, refer to the "Troubleshooting Serial Line Problems" chapter. For information on troubleshooting LAN media, refer to the "Troubleshooting LAN Media Problems" chapter.

Router or End Node Sees Incorrect Designated Router

Symptom: Routers and end nodes see an incorrect or an unexpected designated router. If your network requires a specific router to be elected the designated router, allowing another router to become a designated router can cause unpredictable network behavior and can block connectivity in and out of the area.

Table 9-4 outlines the problems that might cause this symptom and describes solutions to those problems.

Table 9-4 : DECnet: Router or End Node Sees Incorrect Designated Router

Possible Problem	Solution
Priority of the expected designated router is not configured correctly	Step 1 Use the show decnet interface EXEC command to determine which router is the designated router. Note the priority of the router that is shown in the command output. Step 2 If the designated router identified in the output is not the correct router, use the show decnet interface command on the expected designated router and the actual designated router. Step 3 Compare the priority of the actual designated router with that of the expected designated router. The router that you want to be the designated router should have the highest priority. Step 4 If necessary, use the decnet router-priority interface configuration command to give a higher priority to a router so that it will be elected the designated router.
Multiple routers have the same router priority	Step 1 Use the show decnet interface command to determine which router is the designated router. Note the priority of the router that is shown in the command output. Step 2 Use the show decnet interface command on the expected designated router and compare the priorities of the actual and the expected designated routers. Step 3 If the routers have the same priority, use the decnet router-priority interface configuration command to configure a higher priority on the router that should be elected the designated router. Note: If two routers are configured with the same priority, the router with the higher node number will become the designated router.
Adjacency between nodes is not bidirectional	Step 1 Use the show decnet route EXEC command to see if the adjacency with the expected designated router is in a "down" or "initializing" state. Step 2 Use the debug decnet adj privileged EXEC command to determine whether hello packets are being exchanged. Step 3 If a router is not sending hello packets, use the show interfaces command to determine whether the interface input and output queues are full. A full input queue is indicated by a value of 75/75, and a full output queue is indicated by a value of 40/40. Step 4 If the queues are full, and no hello packets are being exchanged, contact your router technical support representative. Step 5 If routers are sending hello packets, contact end-node administrators to determine why end nodes are rejecting hello packets.

Routers Not Establishing Adjacencies

Symptom: Routers do not establish adjacencies with other routers on the same LAN.

Table 9-5 outlines the problems that might cause this symptom and describes solutions to those problems.

Table 9-5 : DECnet: Router Not Establishing Adjacencies

Possible Problem	Solution
More than 32 routers on the network	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 or increase the priority of a router that you want to be adjacent so that it has a higher priority than one of the other neighboring routers. An adjacency will be established with the router you want instead of with a router assigned a lower priority.
Node address out of range	Step 1 Use the show running-config privileged EXEC command to view router configurations. Check to see if the decnet max-address global configuration command has been configured. This command sets the highest DECnet node number allowed in the area. Note: The decnet max-address command specifies the highest node number allowed in an area, not the maximum number of node addresses allowed in an area. For example, if you configure the command decnet max-address 1000 on a router and you configure a node with a node address of 1001, the address is out of range. Step 2 The default maximum address is 1023. However, if another value is configured, the node address might be more than the configured value. If this is the case, increase the maximum address value using the decnet max-address command.
Router area number is higher than configured decnet max-area	If the area number of a DECnet node (such as a router) is higher than the configured decnet max-area value, the adjacency will be reset. Step 1 Use the show running-config privileged EXEC command to view the router configuration. Look for decnet max-area global configuration command entries. This command sets the DECnet maximum area number for the router. Note: The decnet max-area command specifies the highest area value allowed in the network, not the maximum number of areas configurable. For example, if you configure the command decnet max-area 60 and you configure a node with area number 61, the node's area address is out of range. Step 2 Use the show running-config privileged EXEC command to find the area number configured on other DECnet routers. Compare the value configured by the decnet max-area command to the area numbers of other routers. Step 3 If a router's area number is higher than the value configured by the decnet max-area global configuration command, reconfigure the decnet max-area command so that the DECnet maximum area is higher than the area number of all routers.
Adjacency between routers is not bidirectional	Step 1 Use the show decnet route EXEC command to see if the adjacency with the expected designated router is in a "down" or "initializing" state. Step 2 If you are troubleshooting a nonbroadcast multiaccess network (such as Frame Relay or X.25), make sure that map statements are properly configured. Step 3 Use the debug decnet adj privileged EXEC command to determine whether hello packets are being exchanged. Step 4 If a router is not sending hello packets, use the show interfaces command to determine whether the interface input and output queues are full. A full input queue is indicated by a value of 75/75, and a full output queue is indicated by a value of 40/40. Step 5 If the queues are full, and no hello packets are being exchanged, contact your router technical support representative.

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 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 9-6 outlines the problems that might cause this symptom and describes solutions to those problems.

Table 9-6 : DECnet: Routing Node Adjacencies Toggle Up and Down

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 the "Troubleshooting Hardware and Booting Problems" chapter.

No Phase IV Connectivity over Phase V Backbone

Symptom: Communication between DECnet Phase IV areas separated by a 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.