Huawei Quidway S6500 Series Operation Manual page 201

Operation Manual - Routing Protocol
Quidway S6500 Series Ethernet Switches
The backbone area (area 0) cannot be configured as the STUB area and the
virtual link cannot pass through the STUB area. That is, if a virtual link has been
set up between RTB and RTC, neither area1 nor area0 can be configured as a
stub area. In the above figure, only area 2 can be configured as stub area.
Routers in the STUB area cannot redistribute the external routes.
Backbone area must guarantee the connectivity of all nodes.
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Chapter 4 OSPF Configuration