- Cisco Employee,
This is a list of Cisco Wireless related facts that have evoked a “really? well I wish I knew that before…” moment for me and many others.
Hopefully this will help others save some time and frustration.
Please post suggestions for additions, as I’m sure there are other topics that fit these criteria.
Top 10 Cisco Wireless “Good to Know”
1) Controller interface vlan tagging, native vlan 1
Cisco Switches by default do not tag the native vlan. Also by default, the native vlan is 1, therefore vlan 1 is untagged.
When establishing a trunk to a Cisco Wireless LAN Controller, it's important to be aware of how tagged vs untagged are identified.
(4400-A) >show interface summary
Interface Name Port Vlan Id IP Address Type Ap Mgr Guest
--------------- ---- ---------- -------------- ----- ------ -----
ap-manager 1 untagged 22.214.171.124 Static Yes No
management 1 untagged 126.96.36.199 Static No No
When going through a WLC's initial startup wizard, if untagged for the Management Interface’s vlan is desired, enter '0' (zero) when prompted for the management interface's vlan, as this is equivalent to 'untagged':
Welcome to the Cisco Wizard Configuration Tool
Use the '-' character to backup
Would you like to terminate autoinstall? [yes]:
Management Interface VLAN Identifier (0 = untagged): 0
2) AP Image Names: w7 vs w8
ap image names:
w7 = standalone
w8 = lightweight
Lightweight/controller based/capwap/lwapp image:
Cisco IOS Software, C1130 Software (C1130-K9W8-M), Version 12.4(23c)JZ, RELEASE SOFTWARE (fc1) c1130-k9w8-mx.124-23c.JZ
Cisco IOS Software, C1140 Software (C1140-K9W7-M), Version 12.4(21a)JY, RELEASE SOFTWARE (fc1)c1140-k9w7-mx.124-21a.JY
3) AP Part Numbers: LAP vs AP
Most Cisco Access Points are available with two part numbers.
LAPxxx = shipped new from manufacturing with lightweight image
APxxx = shipped new from manufacturing with autonomous image
Same physical hardware.
Same physical ap's, the first is shipped with a lightweight image, the second with an IOS image:
Most AP's can be converted between both modes.
4) Wireless LAN Controller DHCP Handling
Wireless Lan Controllers perform 'dhcp proxy' by default. The ‘Dhcp Server’ IP Address configured on controller interfaces acts the same way as an 'ip helper' statement on a Cisco router.
With this configuration in place, an IP Helper statement on the wireless clients’ default gateway router is not necessary.
DHCP Proxy can be configured via the WLC’s GUI in 6.x and 7.x code (Controller -> Advanced -> DHCP).
Earlier code requires CLI access for configuration:
(WLC) >show dhcp proxy
DHCP Proxy Behaviour: enabled
(WLC) >config dhcp proxy disable
(WLC) >show dhcp proxy
DHCP Proxy Behaviour: disabled
5) Lightweight AP modes: Local vs H-Reap (FlexConnect)
Local mode Access Point: tunnels all traffic to controller, controller responsible for tagging packets and putting them on the wired network, AP's switchport configured in access mode/non trunk.
H-Reap mode Access Point: ap's function similarly to standalone ap's, tag their own traffic, AP's switchport configured as trunk. Vlan tagging requires configuration on each H-Reap mode AP (Via the controller’s Gui).
*H-Reap was renamed to 'FlexConnect' in 7.2 code.
6) Legacy Access Points End of Support
1500 Series, LAP-1505, LAP-1510: Last supported in 4.2.M controller code.
1000 Series, AP1010, AP1020, AP1030: Last supported in 4.2 controller code.
1120/1230 Series, 1121, 1230, etc. Last supported in 7.0 code.
1130, 1240, 1520. Last supported in 8.0 code (no support in 8.1 and later).
Software Release Support for Access Points
These Access Points will not join a controller running code later than supported.
7) AP console settings
•8 data bits
•1 stop bit
*********No hardware flow control******
These are the same settings for other Cisco devices. It is essential that AP's console session have flow control disabled. Most other Cisco devices will tolerate this setting if not disabled, but AP's will not. The result is typically no display and/or keyboard response.
8) WLC Dynamic Interfaces, Does it Route?
Those familiar with Cisco routing and switching may get the impression that Wireless Lan Controllers have routing capability. This may seem apparent due to the fact that multiple dynamic interfaces with ip addresses may be configured. WLC's do not route.
The ip addresses assigned to the dynamic interfaces are not used for client traffic passing through the controller.
Dynamic interfaces' IP addresses primary functions are:
+ Referenced as Giaddr for DHCP Proxy (relay)
+ Multicast. For wireless multicast receivers connected to local mode ap's, if the controller has IGMP snooping enabled, it will proxy/spoof IGMP reports to the wired network using the client's corresponding dynamic interface IP address. If IGMP snooping on the controller is disabled, client IGMP reports are forwarded unmodified to the wired network.
+The IP address is checked when you do an intercontroller roam, so that the WLC knows if you did a L2 or L3 roam, and whether to anchor your traffic or to pass the MSCB entry to the new WLC.
By default, multicast traffic is not forwarded by Wireless Lan Controllers for local mode ap's.
A common source of confusion is that Autonomous Mode AP's will forward multicast just as they would unicast, so no configuration is required. In the instance of Autonomous AP's being converted to Controller Based/Lightweight, multicast will no longer work until configured on the controller.
Since Controller based H-Reap mode ap's forward their own traffic, multicast will behave as if the AP were a standalone AP, and no controller configuration is required.
10) Anchored Wlans. Where does authentication occur?
For Layer 3 authentication, e.g. Web Auth, authentication handling occurs on the Anchor Controller.
For Layer 2 authentication, e.g. 802.1x, authentication handling occurs on the Foreign controller.