Case Study: Wired Users Can Connect to Printers but Wireless Users Cannot

Symptom

As shown in Figure 6-7, wired users can connect to the printer but wireless users cannot.

Figure 6-7 Wired and wireless users connecting to the printer

Relevant Alarms and Logs

None

Cause Analysis

The printer and wired users are located on the same Layer 2 network. The printer and wireless users are connected through a Layer 3 network. To enable communication between them, a gateway needs to be configured on the printer.

Procedure

1. Configure the gateway on the printer so that wireless users can communicate with the printer at Layer 3.

Suggestion and Summary

Services are available to wired users but not wireless users. It seems that a fault occurs on the WLAN. However, the wired network is the ultimate carrier of the WLAN. In most cases, faults may not be caused by the WLAN. Therefore, such simple inference is not logical. When a fault occurs, troubleshoot it step by step, instead of suspecting the WLAN quality before taking any troubleshooting measure. You can find out the cause of this problem only based on basic network knowledge.

This problem is easy to locate but frequently occurs. The common roadmap for handling this type of problems is as follows:

1. Check whether the printer can be pinged. In this case, wired users can ping the printer, but wireless users cannot.
2. If the ping operation fails, the network is disconnected. Check whether the basic entries on the network devices are correct, such as the MAC address table, ARP table, and routing table.
3. Check whether related services, such as ACL and CAR, are configured.
4. Obtain packet headers segment by segment to determine the node where packets are lost.
5. If packet loss occurs on the WLAN device, contact technical support personnel.