Troubleshooting Bonjour

Even though Bonjour is meant to address zero configuration scenarios and requires no management, there might be situations where you will need to troubleshoot Bonjourenabled networks. Here are a few troubleshooting tips that can help you understand what is happening on a network where Bonjour is used. It is helpful to remember that Bonjour is associated with services, not devices. A single device (for example, a Macintosh computer) might have multiple Bonjour services running concurrently (for example, Personal File Sharing, iChat, and iTunes).

Name Conflict Resolution

The Bonjour name is based on the initial installation assistant values entered for First Name and Last Name, and you can modify the Bonjour name in the Sharing pane of System Preferences anytime after the initial configuration. You can type any valid name into this field and Bonjour will map the name to a valid link-local name, as well as check for duplicate name conflicts on the local subnet. If a duplicate name is found, Bonjour will increment the current Bonjour name until a unique name is found. If two users have the Bonjour name jan on the same subnet, one machine may end up with the Bonjour name jan-2.local. To avoid any confusion that might arise from having duplicate names, use names that are most likely to be unique.

Packet Sniffing

Bonjour uses a standard DNS packet format, but on UDP Port 5353 instead of 53. You can use the tcpdump, ethereal, tethereal, or other packet-sniffing tools to monitor Bonjour activity and detect abnormalities. For example, to capture Bonjour packets only using tcpdump, use the following commands:

• sudo tcpdump -i en0 dst port 5353

• sudo tcpdump -i en0 | grep mdns

Log Monitoring

Use Console to view the system log and look for mDNS entries to detect errors or other types of problems. You can also view the mDNS entries in the system log using the following command:

grep mDNS /var/log/system.log