User manual

Chapter 4 - Layer 3 Command Set - IP Networking OSPFv2 (Dynamic Routing Protocol Module)
Alvarion BreezeNET B130/B300 GigE 155 Operational User Manual
The area can be configured as a stub area using the command in config-router
command:
area (A.B.C.D|<0-4294967295>) stub [no-summary]
no-summary option is specified if it is not necessary to advertise a summary ads
of other area's links to this area.
4.7.8.3 Backbone coherence. Virtual links
In general, OSPF protocol requires a backbone area (area 0) to be coherent and
fully connected. I.e. any backbone area router must have a route to any other
backbone area router. Moreover, every ABR must have a link to backbone area.
However, it is not always possible to have a physical link to the backbone area. In
this case between two ABR (one of them has a link to the backbone area) in the
area (not stub area) a virtual link is organized. This can be done using the
following command in config-router mode:
area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D
where:
 (A.B.C.D|<0-4294967295>) - area identifier through which a virtual link goes
 A.B.C.D - ABR router-id with which a virtual link is established. Virtual link
must be configured on both routers. For example:
Router 192.168.152.45:
OSPF> configure
OSPF(config)# router
OSPF(config-router)# area 0.0.0.1 virtual-link 192.168.78.12
Router 192.168.78.12:
OSPF> configure
OSPF(config)# router
OSPF(config-router)# area 0.0.0.1 virtual-link 192.168.152.45
Formally, the virtual link looks like a point-to-point network connecting two ABR
from one area one of which there is a link to backbone area. This pseudo-network
is considered to belong to the backbone area.