Cisco 871 wireless router - part 2

Finally!!! I can get out to Internet wirelessly thru my 871w. It took lots of reading and troubleshooting, but it's working. I had to break down and call for help, so I can't take credit for this myself. Vivek, my Indian guru, solved it for me. I did not have the following 2 lines in my config:

bridge 1 protocol ieee
bridge 1 route ip

The first line establishes the "ieee" type spanning tree protocol for bridge group 1, and , I assume, establishes bridge group 1 in the first place. The second line tells the router to route IP on any interface that has an IP address, even though the interface is in a bridge group.

Without the "bridge 1 route IP" command, then IP ain't routed, it's bridged. To bridge is to forward a packet using layer 2 addressing info (MAC address) instead of layer 3 addressing info (IP address). But it wasn't working, so maybe it wasn't bridging either????????

After I entered that command in my 871 config, The computers connected wirelessly immediately got IP addresses from the dhcp server on the 871 and started being able to talk to Internet.

The BVI interface is something that is new to me. Apparently it is like a group IP mailbox for all the interfaces that don't have IP addresses. In other words, all of the interfaces that are attached to the "switch" portion of the 871 rather than the router portion. Here's the deal: If the 871 were just a plain router with no "virtual switch" built in, then of course it would have an interface with an IP address which was connected by ethernet cable to a physical switch. All the computers would in turn be connected to the switch.

Since that interface to the physical switch does't exist when the switch is built in, the interface is created out of thin air and called a BVI (bridge virtual interface). At lease that's my understanding........

Here are some good commands I learned:

show ip dhcp bindings - a good troubleshooting command that shows what addresses the router's dhcp server has handed out to which MAC addresses


show dot11 associations - also good for troubleshooting. It shows which computers are communicating with the wireless network.

show ip dhcp import - shows what data (dns server addresses, domain name, etc) is being sent to dhcp clients by the dhcp server.