Cisco 800 series Wireless routers: Wireless and Ethernet on the same IP subnet

For a recent customer install of our point of sale products Amicus Retail (POS) and Amicus PDA. The customer requested that the wireless and Ethernet interfaces sit on the same IP subnet.

Normally the 800 series routers are configured with NAT between the WAN and VLAN interfaces, for this setup NAT will be performed between the WAN and a bridging interface. This then allows the VLAN and wireless interfaces to be bridged via this bridging group, thus both interfaces can be placed on the same IP subnet.
The Cisco router used in this example is an 877W router, which has an ADSL interface for it’s WAN Connection. The configuration for other routers in the wireless 800 series range will follow a similar process for the VLAN, Wireless and bridging interfaces, but the WAN interfaces will be model specific.

Configuration of the ADSL dialer interface:
This interface is configured as the external interface for NAT via the “IP Nat outside” command.

Interface Dialer0
Ip address negotiated
Ip mtu 1452
Ip nat outside
Ip virtual-reassembly
Encapsulation ppp
No ip route-cache cef
No ip route-cache
Dialer pool 1
Dialer-group 1
No cdp enable
Ppp authentication chap pap callin
…

Configuration of Bridging
The Bridging interface has been configured as the internal NAT interface via the command “ip nat inside”.
It also has been configured with an IP address via the “ IP address A.B.C.D “; this IP address will be the default gateway for all devices attached to the router.
Other relevant commands are listed below:
“Bridge irb”: enables IRB on router.
“Bridge 1 protocol ieee”: enables bridging on the router.
“Bridge 1 route IP”: enables routing of all IP protocol packets

Bridge irb
…
Bridge 1 protocol ieee
Bridge 1 route ip
!
Interface BVI1
Ip address 192.168.1.1 255.255.255.0
Ip nat inside
Ip virtual-reassembly
!

Configuration of VLAN interface
This interface has been configured with no IP address and as a member of the bridging group via the commands “no ip address” and “bridge-group 1”.

!
Interface Vlan1
No ip address
Ip virtual-reassembly
Bridge-group 1
Bridge-group 1 spanning-disabled
!

Configuration of the Wireless Interface
This interface has been configured as a member of the bridging group via the bridge-group commands listed in the configuration below.

!
Interface Dot11Radio0.1
Encapsulation dot1Q 1 native
No snmp trap link-status
No cdp enable
Bridge-group 1
Bridge-group 1 subscriber-loop-control
Bridge-group 1 spanning-disabled
Bridge-group 1 block-unknown-source
No bridge-group 1 source-learning
No bridge-group 1 unicast-flooding
!