Infrastructure Awareness
Existing Network

Operating Systems and Protocols
Ask the IT representative about the operating systems for the clients and servers. Ask which protocols are being used on the network  lso, ask which protocols will be sent over the WLAN. Protocols that will not be used on the WLAN may need to be filtered out to reduce unnecessary wireless traffic. Make sure that the customer is aware that not all operating systems are supported.

Switches and Hubs
While investigating the network topology and the media, examine the network components. Hubs can be 10 Mbps, 100 Mbps, or a combination of 10/100 Mbps. The Cisco Aironet APs have 10/100 autosensing ports, and will work on either speed. Whenever possible, try to connect using a 100 Mbps-capable port. Many people are not aware of these abilities and will therefore try to use switches the same way a hub would be used. The belief is that all devices plugged into the switch will be able to communicate. This may not be the case, depending on the default settings of the switch. If the customer uses switches, find out how the switches are set up. Switches have the ability for each port to represent a virtual LAN (VLAN). VLANs may be grouped together to form larger VLANs. Switches can stop broadcast packets. However, switches cannot stop broadcast frames. Switches are designed for wired networks with stationary users. Switches are not designed to handle mobile users. Cisco Aironet APs are set up to work with switches. When a client roams from AP1 to AP2, AP2 sends a multicast packet with the source address of the roaming client. The AP then sends this packet for the client, which updates the Content Addressable Memory (CAM) on the switch. AP1 can then forward any packets that it has from the client to AP2.

The customer application may not be set up to handle a switched network. The application may send out broadcast packets. If the client is connected to an AP that is not on the same VLAN as the server, the broadcast packets may never reach their destination. This can vary depending on the configuration of the switch and the setup of the network.

One potential solution to this problem is to form a VLAN by grouping the ports with APs connected to them with the port the host is using. However, this solution may not work for every customer. Another potential solution is to network all of the APs to the same hub that the host uses. Cable distance limitations may make this difficult. Still another possible solution is to network all of the APs together via hubs and have them connect to the same hub the host uses. However, this is not a viable option if the host is remote.

Some hubs may appear to be switches. Remember that a hub is a multiport repeater. All Layer 1 and Layer 2 traffic will be propagated to and from an AP. The AP, hub, and any Layer 1 device that is directly connected will see all traffic. However, it is better to connect an AP or wireless bridge to a switch. If Layer 3 broadcast control is required, then a router should be used to connect between the WLAN and the wired LAN.

Some Cisco switches can provide power to the AP or bridge via Ethernet. Networks which utilize Cisco IP phones will most likely have powered switches in place. Power switches or Cisco Aironet Power Injector modules help eliminate the need to run a separate AC power source to the AP or bridge.

Routers
Routers present many of the same challenges as switches. Like switches, routers do not pass broadcast packets. Again, this may present a problem for the application or for clients trying to use DHCP. Routers may also indicate that they intend to use a remote host. If this is the case, it may be necessary to enter a static route in the router.