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Cisco 851W: Configure a wireless LAN

Originally published Last updated

While preparing a Cisco 851W router for a SOHO installation, I ran into a few issues. I tried the HTTP interface but soon found that it was not the right approach for me. I had configured many switches, routers and access points, but never an integrated device like the 851W.

In the default configuration, VLAN1 had a static IP address in the 10.x.x.x range. I changed that address and started configuring the wireless LAN before moving on to NAT and VPN. After two hours of trying different configurations, I got it working.

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bridge irb

!interface Dot11Radio0
 no ip address
 !
 encryption vlan 1 mode ciphers tkip
 !
 broadcast-key vlan 1 change 30
 !
 ssid networknet
 !
 speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 12.0 18.0 24.0 36.0 48.0 54.0
 station-role root
!
interface Dot11Radio0.1
 encapsulation dot1Q 1 native
 no cdp enable
 bridge-group 1
 bridge-group 1 subscriber-loop-control
 bridge-group 1 spanning-disabled
 bridge-group 1 block-unknown-source
!
interface Vlan1
 no ip address
 bridge-group 1
 bridge-group 1 spanning-disabled
!
interface BVI1
 ip address 192.168.142.1 255.255.255.0
 ip nat inside
 ip virtual-reassembly
!

Resolve the interface and DHCP issues

I tried assigning static IP addresses to both BVI1 and VLAN1, but they overlapped. I then removed the IP address from VLAN1 and assigned it only to BVI1. This got the wireless LAN working with a WPA key and DHCP enabled.

One issue remained: a device connected to ports Fa0 - Fa3 did not receive an address from the DHCP pool. I found a post about assigning a bridge-group to VLAN1. That worked, and I am now almost finished configuring the router.

The Cisco 851W example configuration shows the configuration I used for my router.

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