SignaMax 065-7434, Руководство по настройке

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The virtual connection is identified by the Router-ID of the OSPF process
at the other side.
The two routers configured with the virtual connection must be in the
same common area, which is called the transmission area (transit area)
of the virtual connection.
The virtual connection can be regarded as a part of the backbone, that is,
unnumbered point-to-point network. Its cost is that of the connection
and cannot be configured.
Each virtual connection is identified by the Router ID at the peer side of
the transit area and virtual connection.
The link of the virtual connection is set up by searching Router ID on the
SPF tree after the SPF calculation.
To cancel the configuration command of the virtual connection, use the
no area virtual-link command.
The virtual connection cannot be set via the stub or NSSA area, that is,
the transit area of the virtual connection cannot be stub or NSSA area.
C o n f i g u r e O S P F De m a n d C i r c u i t s
The demand circuit is the network whose cost varies with the use. The
cost can be based on connection time and transmitted packet bits. The
typical demand circuits include ISDN circuit, X.25SVC, and dial-up. Even
after the neighboring status is FULL, the OSPF needs to send and receive
hello packets regularly and needs the next-layer data link to be opened,
which results in unnecessary cost. After adding the demand circuit
function, the hello packets and route update information of OSPF need to
be suppressed on the demand circuit. When there is no data to be
transmitted, allow the next-layer data link to be closed.
On the demand circuit, the hello packets and LSAs are sent only when
initializing the neighbor or the topology changes. If the route needs to be
re-calculated because there are important changes on the topology, the