Local controllers are unable to establish a tunnel with the VLAN that is available on network seed controller while another network seed is down.
Network topology:
Controller A
Controller B
Controller C
Controller D
Cluster:
Controller A & B are in a cluster
Controller C & D are in a cluster
Network domain:
Controller C & D are Network domain seeds with A & B as network domain member controllers.
When Controller C (network seed) is down, the controllers A and B are unable to establish a tunnel with a VLAN, which is available in Controller D (network member seed).
In a network domain, when a WLC is configured as seed of a network domain, it is required to be configured as a member of its own network domain to make the seed share its available VLANs over the network domain members.
In the case of multiple seeds present over a network domain, the configuration must be associated with a higher affinity for its own seed-ip so that seeds join as member in its own domain as primary and shares its available VLANs to other network domain members.
Controller C & D should be added themselves as Network member seeds so that they can start advertising their local VLANs when Network seed is down.
Example Configuration
Controller C: 192.168.10.18
set mobility-domain mode seed domain-name JTAC-Guest
set mobility-domain member 192.168.10.26
set network-domain mode seed domain-name JTAC-NEDO
set network-domain peer 192.168.10.26
set network-domain mode member seed-ip 192.168.10.26
Controller D: 192.168.10.26
set mobility-domain mode secondary-seed domain-name JTAC-Guest seed-ip 192.168.10.18
set network-domain mode seed domain-name JTAC-NEDO
set network-domain peer 192.168.10.18
set network-domain mode member seed-ip 192.168.10.18
Controller A: 10.20.192.240
set mobility-domain mode seed domain-name JTAC-Guest-local
set mobility-domain member 10.22.192.240
set network-domain mode member seed-ip 192.168.10.26
set network-domain mode member seed-ip 192.168.10.18
Controller B: 10.21.10.240
set mobility-domain mode secondary-seed domain-name JTAC-Guest-local seed-ip 10.20.192.240
set network-domain mode member seed-ip 192.168.10.18
set network-domain mode member seed-ip 192.168.10.26
In order to enable network seeds to advertise their local VLANs, add them as member controllers of their own network domain:
set network-domain mode member seed-ip 143.216.48.18 affinity 10
set network-domain mode member seed-ip 143.216.48.26 affinity 10