Примечания к выпуску для Cisco Cisco 4404 Wireless LAN Controller
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Release Notes for Cisco Wireless LAN Controllers and Lightweight Access Points for Release 3.2.171.5
OL-11567-01
Important Notes
Important Notes
This section describes important information about the controllers and access points.
Access Points Fail to Join Controllers If MTU Setting Is Less Than 1500
When the network path between access points and the controller is configured for an MTU size less than
1500, the controller does not receive join requests from access points in local mode. (MTU settings less
than 1500 are common when you use tunneling protocols such as IPsec VPN, GRE, and MPLS.) The
access point join request is larger than 1500 bytes, so the request is fragmented. The size of the first
fragment is 1500 bytes (including IP and UDP header) and the second fragment is 54 bytes (including
IP and UDP header).
1500, the controller does not receive join requests from access points in local mode. (MTU settings less
than 1500 are common when you use tunneling protocols such as IPsec VPN, GRE, and MPLS.) The
access point join request is larger than 1500 bytes, so the request is fragmented. The size of the first
fragment is 1500 bytes (including IP and UDP header) and the second fragment is 54 bytes (including
IP and UDP header).
Access points in REAP mode are not affected by this limitation, and the problem is resolved in the 4.0
release train because the LWAPP tunnel can reassemble up to 4 fragments. The problem occurs when all
four of these conditions exist on your network:
release train because the LWAPP tunnel can reassemble up to 4 fragments. The problem occurs when all
four of these conditions exist on your network:
•
Your controller runs release 3.2 or earlier
•
Your controller is configured for Layer 3 LWAPP
•
The network path MTU between the access point and the controller is less than 1500 bytes
•
The access point is in local access point (LAP) mode (not REAP mode)
Workarounds
Use one of these workarounds to resolve the problem on your network:
•
Upgrade to controller software release 4.0 if the controller platform supports it.
•
Use 1030 series access points in REAP mode for locations reachable through low-MTU paths.
•
Increase the network path MTU to 1500 bytes.
Changing the Default Values of SNMP Community Strings
The controller has commonly known default values of “public” and “private” for the read-only and
read-write SNMP community strings. Using these standard values presents a security risk. Therefore,
Cisco strongly advises that you change these values.
read-write SNMP community strings. Using these standard values presents a security risk. Therefore,
Cisco strongly advises that you change these values.
Using the GUI to Change the SNMP Community String Default Values
Follow these steps to change the SNMP community string default values through the controller GUI.
Step 1
Click Management and then Communities under SNMP. The SNMP v1 / v2c Community page appears.
Step 2
If “public” or “private” appears in the Community Name column, click Remove to delete this
community.
community.
Step 3
Click New to create a new community.
Step 4
When the SNMP v1 / v2c Community > New page appears, enter a unique name containing up to 16
alphanumeric characters in the Community Name field. Do not enter “public” or “private.”
alphanumeric characters in the Community Name field. Do not enter “public” or “private.”