Troubleshooting DECnet Connectivity

Connection Attempts to DEC Hosts Fail over Routers (Router Configuration)

Symptom: DECnet nodes are unable to communicate when attempting to make connections over routers. This module focuses on possible causes related to router configuration. The next module, "Connection Attempts to DEC Hosts Fail over Routers (End Nodes)," addresses end node issues. Table 7-1 outlines possible causes and suggested actions when connection attempts to DEC hosts fail due to router configuration problems.

Table 7-1 : DECnet: Connection Attempts to DEC Hosts Fail over Routers (Router Configuration)

Possible Causes	Suggested Actions
DECnet not enabled	Step 1 Use the write terminal privileged EXEC command to determine whether appropriate DECnet global configuration and interface command specifications are included in the configuration of the router. Step 2 Enable as required on router and interface.
End nodes not in the same area	Step 1 Check the configuration for the address of the router. Step 2 If end nodes are not in the same area, verify that routers with which these end nodes can communicate are able to reach a Level 2 router.
Actual cost to the destination area is more than the configured cost (Level 1 routers)	Step 1 Use the show decnet interface EXEC command to determine the configured maximum cost. Step 2 Use the show decnet route EXEC command to determine the actual cost to the destination. Step 3 If the actual cost is more than the configured maximum cost, use the decnet max-cost global configuration command to increase the maximum cost.
Actual cost to the destination area is more than the configured cost (Level 2 routers)	Step 1 Use the show decnet interface command to determine the configured maximum area cost. 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 cost, 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 (Level 1 routers)	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, use the decnet max-hops global configuration command to increase the maximum hops.
Actual number of hops to the destination area is more than the configured maximum number of hops (Level 2 routers)	Step 1 Use the show decnet interface command to determine the maximum number of hops configured for intra-area routing. Step 2 Use the show decnet route EXEC command to determine the actual number of hops to the destination area as shown in the DECnet routing table. Step 3 If the actual number of hops to an area is more than the configured maximum hops to an area, use the decnet areamaxhops global configuration command to increase the maximum number of hops.
Access list is improperly applied to DECnet interface	Step 1 Use the show decnet interface EXEC command to determine whether an access list is set. Step 2 If an access list is applied to the interface, use the write terminal privileged EXEC command to determine whether any access list entry in the list denies required access. Step 3 Use the debug decnet connects privileged EXEC command to determine whether the relevant packets are being permitted. Step 4 Use the no decnet access-group interface configuration command to disable the access list on the affected interface. Step 5 Determine whether connectivity is restored. If so, the access list is probably the problem. Step 6 Remove all the access list statements that apply to the interface, and use the decnet access-group interface configuration command to reenable the access control for the interface. Step 7 Enter one access list statement, and test connectivity to the destination address. Repeat until connectivity is lost, at which point you have found the problem access list. Step 8 Modify the access list as necessary.
Improperly enabled Address Translation Gateway (ATG)	Step 1 Use the show decnet map EXEC command to determine whether address mapping is configured properly. Step 2 If address mapping is not configured properly, modify mapping using the decnet first-network map virtual-address second-network real-address global configuration command.
Node address out of range	Step 1 Use the write terminal privileged EXEC command to determine whether the DECnet maximum address has been set for any routers. Step 2 Use the decnet max-address global configuration command to verify that the DECnet maximum address is 1023 (the default). If the node address is more than the decnet max-address value, increase the decnet max-address value.
Partitioned area	Step 1 Review your network topology for any discontiguous areas. Step 2 If any discontiguous areas exist, reconfigure the topology by changing area addresses or by adding a path (router) to create a contiguous network.

Connection Attempts to DEC Hosts Fail over Routers (End Nodes)

Symptom: Whenever a user attempts to connect to a DEC host over a router, the connection attempt fails. The previous module, "Connection Attempts to DEC Hosts Fail over Routers (Router Configuration)," focuses on issues relating to router configuration and implementation. This module focuses on possible causes associated with end nodes. Table 7-2 outlines possible causes and suggested actions when connection attempts to DEC hosts fail due to end node problems.

Table 7-2 : DECnet: Connection Attempts to DEC Hosts Fail over Routers (End Nodes)

Possible Causes	Suggested Actions
Host access control rejects connection (Ultrix target system); user sees the following message: connect failed, access control rejected (typically a session layer problem)	Step 1 Make sure that the following requirements are satisfied: User-supplied access control information is correct. Proxy access is set up correctly. Proxy database and proxy account are correct. Step 2 Make sure that the user's security access matches the access specifications for the user on the remote systems. Step 3 Make changes as necessary.
Unrecognized object (Ultrix target system); user sees the following message: connect failed, unrecognized object	Step 1 Use the NCP tell command to determine whether the object is defined on the target node. The format of the tell command is as follows: tell target-node-name show known objects Step 2 If the object is not defined, log in to the superuser account and run NCP to define the object with the NCP set command, as follows: set object object-id Step 3 After the object is defined, use the NCP tell command to determine whether the object has a file specified: tell target-node-name show object object-id character Step 4 Exit NCP and use the following command to determine whether the file specified for the object exists: ls -l Step 5 If the file for the requested object does not exist, create the file. Step 6 Make sure the protection for the specified file is correct. Example: # chmod a+x /usr/etc/fal# chmod a+x /usr/etc
Insufficient resource error (VMS target system); VMS user sees the following message: % system-E-REMRSC, insufficient system resource at remote node (This error message may not indicate a problem. These parameter values can be set intentionally to prevent network connections beyond a certain number.)	Step 1 Try tuning DEC target system parameters. SYSGEN parameters: - MAXPROCESSCNT NCP parameters: - MAXIMUM LINKS - ALIAS MAXIMUM LINKS AUTHORIZE parameters: - MAXJOBS - MAXACCTJOBS
Invalid login attempted	Step 1 Determine whether access to a host is actually required. Step 2 Ask the system manager at the target node to set up the user's account.

End Nodes Cannot Find a Designated Router

Symptom: When end nodes are unable to see a designated router, they cannot access any nodes that are on different LANs. Other nodes connected to the same LAN are accessible. Table 7-3 outlines possible causes and suggested actions when end nodes cannot find a designated router.

Table 7-3 : DECnet: End Nodes Cannot Find a Designated Router

Possible Causes	Suggested Actions
DECnet not enabled on a router or not enabled on the interface	Step 1 Use the write terminal privileged EXEC command to determine whether the router configuration includes the appropriate DECnet global configuration and interface command specifications. Step 2 Enable DECnet as required on routers and interfaces.
Router not adjacent to the end node	Step 1 At a router believed to be adjacent to the end node, use the debug decnet packets privileged EXEC command to determine whether hello packets are being exchanged between the end node and the router. If hello packets are not being exchanged, the router and the end node may not be adjacent. Step 2 Make sure the router and end node are on the same LAN.
Routers and end node are not in the same area	Step 1 Check DECnet addresses of the routers to determine whether they are in the same area. Step 2 If not, use the decnet routing decnet-address global configuration command to reconfigure the appropriate routers to be in the same area.
Hello packets are not being exchanged	Step 1 Use the debug decnet packets privileged EXEC command to determine whether the router is sending hello packets that are being received by the relevant end node. Step 2 If no exchange is occurring, 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 3 If the queues are full and no hello packets are being exchanged, contact your router technical support representative.

Router or End Node Sees Unexpected Designated Routers

Symptom: If your network requires a specific router to be identified as 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 7-4 outlines possible causes and suggested actions when routers and end nodes see unexpected or incorrect designated routers.

Table 7-4 : DECnet: Router or End Node Sees Unexpected Designated Routers

Possible Causes	Suggested Actions
Router is not adjacent to expected designated router	Step 1 At a router believed to be adjacent to the expected designated router, use the debug decnet packets privileged EXEC command to determine whether hello packets are being exchanged between the routers. If hello packets are not being exchanged, the routers may not be adjacent. Step 2 Make sure the router and end node are on the same LAN.
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. Step 2 Use the show decnet interface command on the expected designated router and the actual designated router. Note the priority of the router. Step 3 Compare the router priorities. The router that you want to be the designated router should have the highest priority. Step 4 If a change is required, use the decnet router-priority interface configuration command to specify a particular router as 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. Step 2 Use the show decnet interface command on the expected designated router and the actual designated router. Step 3 If the routers have the same priority, modify the configurations so that the router that is intended to be the designated router has the highest node number or router priority.
Adjacency with expected designated router is in a "down" or "initializing" state (adjacency between nodes is not bidirectional)	Step 1 Use debug decnet packets privileged EXEC command to determine whether hello packets are being exchanged. Step 2 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 3 If the queues are full, and no hello packets are being exchanged, contact your router technical support representative. Step 4 If routers are sending hello packets, contact end node administrators to determine why end nodes are rejecting hello packets.

Intermittent DECnet Host Connectivity over Router

Symptom: Connections sometimes drop unexpectedly, or hosts are sometimes inaccessible when connections are attempted over a router. Table 7-5 outlines possible causes and suggested actions for intermittent DECnet host connectivity over a router.

Table 7-5 : DECnet: Intermittent DECnet Host Connectivity over Router

Possible Causes	Suggested Actions
Misconfigured router (timers improperly configured)	Step 1 Use the show decnet interface EXEC command to verify that hello timers and routing update timers are consistent among all routers in the network. Step 2 Use the decnet hello-timer and decnet routing-timer interface configuration commands to make any necessary configuration changes.
Disabled serial link or network media	Step 1 Refer to the discussion of media problems in Chapter 2, "Troubleshooting Router Startup Problems," for a general discussion of media problems. Step 2 Refer to Chapter 3, "Troubleshooting Serial Line Problems," for procedures that isolate serial interconnection problems.

Router Cannot Establish Adjacency with Another Router on the Same LAN

Symptom: Router will not establish adjacency with any other routers known to be on the same LAN. Table 7-6 outlines possible causes and suggested actions when a router cannot establish adjacency with another router on the same LAN.

Table 7-6 : DECnet: Router Cannot Establish Adjacency with Another Router on LAN

Possible Causes	Suggested Actions
More than 32 routers on the network	Step 1 Enable the debug decnet routing privileged EXEC command to determine whether the adjacency is being rejected. Step 2 If the adjacency is being rejected, reduce the number of adjacent routers or change the priority of a router that you require to be adjacent so that it has a higher priority than one of the other neighboring routers. (Adjacency will be established with the target router instead of a router eliminated from the environment or assigned a lower priority.)
Node address out of range	Step 1 Use the write terminal privileged EXEC command to determine whether the DECnet maximum address has been set for any routers. Step 2 Use the decnet max-address global configuration command to verify that the DECnet maximum address is 1023 (the default). If the node address is higher than the decnet max-address value, increase the decnet max-address value.
Node area is more than decnet max-area configured	Step 1 Use the write terminal privileged EXEC command to determine whether the DECnet maximum area has been set for any routers. Step 2 Use the decnet max-area global configuration command to verify that the DECnet maximum area is more than the area of the node. If the area of the node is more than the decnet max-area value, the router will reset the adjacency.

No Phase IV Connectivity over Phase V Backbone

Symptom: Phase IV DECnet nodes are able to communicate with each other within a Phase IV area, but cannot access Phase IV nodes on the other side of a Phase V DECnet backbone. Table 7-7 outlines possible causes and suggested actions when there is no Phase IV connectivity over a Phase V backbone.

Table 7-7 : DECnet: No DECnet Phase IV Connectivity over Phase V Backbone

Possible Causes	Suggested Actions
Misconfigured router (area addresses)	Step 1 Enable the debug clns packet privileged EXEC command to determine whether packets are being converted and sent out to DECnet Phase V. Step 2 Use the write terminal privileged EXEC command to verify that DECnet area address (specified by the decnet routing global configuration command) agrees with the CLNS area address (specified by the network router configuration command). (These addresses can be misconfigured easily. The area address for DECnet is specified in decimal, while the area address for CLNS is specified in hexadecimal.) Step 3 If the area addresses do not agree, modify them as necessary.
Misconfigured router (ISO CLNS or DECnet not enabled on relevant interfaces)	Step 1 Use the write terminal command to verify that DECnet and ISO CLNS are enabled on all interfaces where conversion will occur. Step 2 Enable routing on relevant interfaces as necessary. (For DECnet, use the decnet cost interface configuration command; for ISO CLNS, use one of the valid variations of the clns router interface configuration commands.)

Service Requests Are Aborted

Symptom: When a node requests downline load services from a Maintenance Operation Protocol (MOP) server, a display similar to the following appears and repeats on the DEC system console:

%%%%%%%%%%% OPCOM 30-JUN-1993 12:55:08.65 %%%%%%%%%%%%        
Message from user DECNET on Wheel
DECnet event 0.7, aborted service request
From NODE 2.1 (Wheel), 30-JUN-1993 12:55:08.65
Circuit UNA-1, Line open error

Table 7-8 : DECnet: Service Requests Are Aborted

Possible Cause

Suggested Actions

Target system cannot locate matching hardware address, Ethernet address, or load file associated with node requesting service

Step 1 At the DEC system console, look for an OPCOM message that indicates DECnet event 0.7. Step 2 Check the node database on the MOP server for correct setup (proper hardware address, Ethernet address, and load file) for the requesting node. Step 3 Add any missing information or correct errors in the database as needed. Step 4 Power cycle the requesting node to determine whether it is able to obtain its downline load.

Routing Node Adjacencies Toggle Up and Down

Symptom: The following output 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)

Table 7-9 : DECnet: Routing Node Adjacencies Toggle Up and Down

Possible Causes	Suggested Actions
Hardware problem with routing node is causing a conflict between the designated router and another routing node	Step 1 At the DEC system console, look for OPCOM message pairs that indicate DECnet events 4.16 (adjacency rejected) and 4.15 (adjacency up) for specific routing nodes. Step 2 Find the routing node or nodes that are causing the adjacency to toggle. Step 3 Troubleshoot the Ethernet cable or network interface card on the suspect nodes. (For details about isolating router hardware problems, refer to the hardware troubleshooting information in the "Troubleshooting Serial Line Problems" chapter.)
Total number of routing nodes in the network is more than 32	Step 1 Enable debug decnet routing to determine whether the adjacency is being rejected. Step 2 If the adjacency is being rejected, reduce the number of adjacent routers.

DECnet Phase IV Prime Host Cannot Communicate over Router

Symptom: End nodes attached to a Token Ring segment are unable to communicate with hosts on the other side of a router. These end nodes are PCs running Pathworks 4.1.a. The hosts on the other side of the router are Novell-based servers. Table 7-10 outlines a possible cause and suggested actions when a Phase IV Prime host cannot communicate over a router.