Operation Manual - Routing Protocol
Quidway S3500 Series Ethernet Switches Chapter 4 OSPF Configuration
Huawei Technologies Proprietary
4-16
By default, summarization of imported routes is disabled.
After the summarization of imported routes is configured, if the local router is an
autonomous system border router (ASBR), this command summarizes the imported
Type-5 LSAs in the summary address range. When NSSA is configured, this command
will also summarize the imported Type-7 LSA in the summary address range.
If the local router works as an area border router (ABR) and a router in the NSSA, this
command summarizes Type-5 LSAs transformed from Type-7 LSAs. If the router is not
the router in the NSSA, the summarization is disabled.
4.2.18 Configuring OSPF Virtual Link
According to RFC2328, after the area division of OSPF, not all the areas are equal. In
which, an area is different from all the other areas. Its area-id is 0.0.0.0 and it is usually
called the backbone Area. The OSPF routes between non-backbone areas are
updated with the help of the backbone area. OSPF stipulates that all the non-backbone
areas should maintain the connectivity with the backbone area. That is, at least one
interface on the ABR should fall into the area 0.0.0.0. If an area does not have a direct
physical link with the backbone area 0.0.0.0, a virtual link must be created.
If the physical connectivity cannot be ensured due to the network topology restriction, a
virtual link can satisfy this requirement. The virtual link refers to a logic channel set up
through the area of a non-backbone internal route between two ABRs. Both ends of the
logic channel should be ABRs and the connection can take effect only when both ends
are configured. The virtual link is identified by the ID of the remote router. The area,
which provides the ends of the virtual link with a non-backbone area internal route, is
called the transit area. The ID of the transit area should be specified when making
configuration.
The virtual link is activated after the route passing through the transit area is calculated,
which is equivalent to a p2p connection between two ends. Therefore, similar to the
physical interfaces, you can also configure various interface parameters on this link,
such as hello timer.
The "logic channel" means that the multiple routers running OSPF between two ABRs
only take the role of packet forwarding (the destination addresses of the protocol
packets are not these routers, so these packets are transparent for them and the
routers forward them as common IP packets). The routing information is directly
transmitted between the two ABRs. The routing information herein refers to the type-3
LSAs generated by the ABRs, for which the synchronization mode of the routers in the
area will not be changed.
Perform the following configuration in OSPF Area view.
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