Cisco IOS Software Release 12.4(3)c runs on the 2811 Integrated Services Router (ISR), and it does not support the Wireless LAN Controller Module (WLCM).
The Interface WLAN-Controller 1/0 line protocol can also fail.
Upgrade the Cisco IOS software on the 2811 ISR to Cisco IOS Software Release 12.4(6)T. This enables the WLCM to be recognized on the ISR. As a temporary solution turn off the keepalive on the controller interface.
Cisco IOS Software Release 12.4(6)T, which is also called Cisco IOS Software Release 12.4(3rd release)T, is not Cisco IOS Software Release 12.4(3)T. These Cisco IOS software releases can also be used:
Cisco IOS Software Release 12.4(2)XA1
Cisco IOS Software Release 12.4(3rd release)T or later
The WLCM allows small and medium-sized businesses (SMBs) and enterprise branch offices to cost-effectively deploy and manage secure wireless LANs (WLANs). The module provides unparalleled security, mobility, and ease of use for business-critical WLANs and delivers the most secure enterprise-class wireless system available. As a Cisco ISR module, it delivers:
centralized security policies
wireless intrusion prevention system (IPS) capabilities
Quality of Service (QoS)
Layer 3 fast secure roaming for WLANs
The WLCM manages up to six Cisco Aironet lightweight access points and is supported on these routers: