Logical channel refers to two ABR between the multiple running OSPF router is only the role of a forwarding message, because the protocol message destination address is not these routers, so these messages for them is transparent, where the routing information is generated by the ABR, the LSA, The router lsdb in the zone does not change the way it synchronizes.
A link is a zone that cannot be linked to zone 0 that causes some networks to be unreachable, because some regions divide the area 0 into multiple OSPF autonomous systems. Link settings should be noted:
First of all, if the network topology constraints can not guarantee physical connectivity, can be created by creating a virtual connection to meet this requirement, virtual connection refers to the two ABR through a non-backbone region within the routing of the region to establish a logical connection channel. A zone that provides an internal route to a non-backbone region for both ends of a virtual connection is called a transformation zone, and its area number Area-id must also be specified at configuration time. Both ends must be ABR and must be configured at both ends to take effect, and the virtual connection is identified by the ID number of the end-to-end router.
Second, the virtual connection is activated after the route through the transformation area is computed, which is equivalent to a point-to-point connection between the two endpoints, so that the parameters of the interface can be configured on this connection as well as the physical interface.
Finally, and most importantly, the virtual connection refers to the two ABR, through a non-backbone region, the establishment of a logical connection channel, can be understood as two ABR there is a point-to-point connection between the logical channel " Refers to two sets of ABR between the multiple running OSPF router is only a forwarding message role, because the protocol message destination address is not these routers, so these messages for them is transparent, just as a common IP message forwarding, two ABR direct routing information between.
Routing aggregation is the process of merging multiple routes into a single route, usually on ABR, and it is a technique for organizing network layer IP addresses in a hierarchical way so that addresses have "topological importance." Main performance:
First, once the aggregation network segment of a network is added to the zone, all the internal routes of the IP addresses that fall within the aggregation segment are no longer broadcast independently to other regions, but only the routing information of the entire aggregated network segment. The exchange of routing information between regions can be reduced by receiving the aggregation network segment and the qualification of the network segment.
Second, a zone can configure routing aggregations multiple times. When ABR sends routing information to other areas, it generates SUM_NET_LSA in a network segment. When routing information is processed in ABR, only one aggregate route is sent for a network segment configured with routing aggregation. If there are contiguous segments of the network in this area, you can use the Abr-summary command to aggregate these contiguous segments into a single segment of the network. In this way, ABR sends only one aggregated LSA, and any LSA within the aggregate network segment specified by this command will no longer be sent separately, thereby reducing the size of other regional link state database LSDB. These are the various protocols and methods you need to know when setting up some high-end routers.