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When you are manually allocating IP addresses, Cisco recommends that you make IP addressing changes
from the furthest mesh access point child first and then work your way back to the RAP. This also applies
if you relocate equipment. For example, if you uninstall a mesh access point and redeploy it in another
physical location of the mesh network that has a different addressed subnet.
Another option is to take a controller in Layer 2 mode with a RAP to the location with the misconfigured
MAP. Set the bridge group name on the RAP to match the MAP that needs the configuration change.
Add the MAP's MAC address to the controller. When the misconfigured MAP comes up in the mesh
access point summary detail, configure it with an IP address.
Misconfiguration of DHCP
Despite the DHCP fallback mechanism, there is still a possibility that a mesh access point can become
stranded, if any of the following conditions exist:
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These conditions can strand a mesh access point that is configured with or without a wrong static IP
address or with DHCP. Therefore, it is necessary to ensure that when a mesh access point is unable to
connect after exhausting all DHCP discovery attempts or DHCP retry counts or IP gateway resolution
retry counts, it attempts to find a controller in Layer 2 mode. In other words, a mesh access point
attempts to discover a controller in Layer 3 mode first and in this mode, attempts with both static IP (if
configured) or DHCP (if possible). The AP then attempts to discover a controller in Layer 2 mode. After
finishing a number of Layer 3 and Layer 2 mode attempts, the mesh access point changes its parent node
and re-attempts DHCP discovery. Additionally, the software exclusion-lists notes the parent node
through which it was unable to obtain the correct IP address.
Identifying the Node Exclusion Algorithm
Depending on the mesh network design, it is entirely possible that a node finds another node "best"
according to its routing metric (even recursively true), yet it is unable to provide the node with a
connection to the correct controller or correct network. It is the typical honeypot access point scenario
caused by either misplacement, provisioning, design of the network, or by the dynamic nature of an RF
environment exhibiting conditions that optimize the AWPP routing metric for a particular link in a
persistent or transient manner. Such conditions are generally difficult to recover from in most networks
and could blackhole or sinkhole a node completely, taking it out from the network. Possible symptoms
include, but are not limited to:
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Cisco mesh software tackles this difficult scenario using a sophisticated node exclusion-listing
algorithm. This node exclusion-listing algorithm uses an exponential backoff and advance technique
much like TCP sliding window or 802.11 MAC.
Cisco Aironet 1520, 1130, 1240 Series Wireless Mesh Access Points, Design and Deployment Guide, Release 6.0
OL-20213-01
There is no DHCP server on the network.
There is a DHCP server on the network, but it does not offer an IP address to the AP, or if it gives a
wrong IP address to the AP (for example, on a wrong VLAN or subnet).
A node connects to the honeypot, but cannot resolve the IP gateway when configured with static IP
address, or cannot obtain the correct IP address from DHCP server, or cannot connect to a WLAN
controller.
A node ping-pongs between a few honeypots or circles between many honeypots (in worst-case
scenarios).
Troubleshooting
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