System information

Troubleshooting DECnet 11-261

DECnet: 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 11-4 outlines the problems that might cause this symptom and describes solutions to those

problems.

Table 11-4 DECnet: Router or End Node Sees Incorrect Designated Router

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 Caution: Because debugging output is assigned high priority in the CPU

process, it can render the system unusable. For this reason, use debug

commands only to troubleshoot specific problems or during troubleshooting

sessions with Cisco technical support staff. Moreover, it is best to use debug

commands during periods of lower network trafﬁc and fewer users. Debugging

during these periods decreases the likelihood that increased debug command

processing overhead will affect system use.

Step 3 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 4 If the queues are full and no hello packets are being exchanged, contact your

technical support representative.

Step 5 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 Chapter 15, “Troubleshooting

Serial Line Problems.” For information on troubleshooting LAN media, refer to the

media troubleshooting chapter that covers the media type used in your network.

Possible Problem Solution