Summit WM3000 Series SW v5.1 – Clustering
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AP Adoption and failover
One benefit from clustering is AP redundancy. If one member of the cluster fails, all the access points will transition to the
working controller with no downtime to clients. Access Points will only adopt to an active member in a cluster. In the case
of an active/standby cluster, all APs will adopt to the active controller. If the active controller fails, the APs will then be
adopted by the standby WLAN controller. APs adopt to a WLAN Controller through the following process:
1. APs learn about Controllers using Link State Packets (LSPs) exchanged over MiNT links
2. APs send Load Request packets to each Wireless Controller discovered
3. Each Controller responds with a load response (Licensed APs minus Adopted APs)
4. The Access Point will select the best Wireless Controller based on the following criteria:
a. Layer 2 Connection
b. The Wireless Controllers Group
c. Wireless Controller Load
5. AP adopts and receives configuration from the Wireless Controller
For access points to discover the cluster at Layer-2, no extra configuration is required. Simply plug in the APs and make
sure they are in the same VLAN as the cluster. For access-points that cross a Layer 3 boundary, a DHCP server needs to
provide them with IP addresses, as well as the required DHCP/DNS options to discover the WLAN controllers. Legacy
DHCP option 189 is still supported in SW v5.1. It is used as a string value that will contain a list of WLAN controllers IP
addresses that the APs should connect to.
New in SW v5.1 is DHCP option 191. It supercedes option 189 and supports additional parameters. The contents of
option 191 are a series of tag value fields separated by semicolons.
Neither the tag fields, nor the value fields can contain ‘=' or ';' characters. There is no whitespace between tag/value pairs
or between a tag and its value.
Recognized tags:
•
pool1 – List of comma separated IP addresses or hostname comprising controller group 0
•
pool2 – List of comma separated IP addresses or hostname comprising controller group .
•
Level – Integer (1 | 2) indication the MiNT link level for IP links
•
Udp-port – Tunnel port for MiNT communication over UDP/IP
•
Area-id – MiNT area id for discovery
•
Remote – Indicates remote MiNT link; substitute for ‘level=’ tag
•
Force – Force to create MiNT link, even when the link is not required. Default behavior is to create on-demand
link.
Once the DHCP option is received, APs send discover messages to each IP address in the group (random order) and wait
for offers. Upon receiving a offer, the device with lowest load is chosen. Each group is communicated with twice before
the AP moves on to the group with the lower preference. Controller group ‘pool1’ always has the higher preference.
Example:
# option definitions common to all supported networks.
option MLCP code 191 = string;
default-lease-time 3600;
max-lease-time 7200;
authoritative;
subnet 192.168.30.0 netmask 255.255.255.0 {
