Set router aggregation and link Methods

When setting up some high-end routers, You Need To Know various protocols and methods.

1. Route aggregation is usually implemented by combining multiple routes into one route on the ABR. It is a technology that organizes network layer IP addresses in a hierarchical manner so that addresses have "topological importance.

1. When the routing information is processed in the ABR, only one aggregation route is sent for a CIDR Block configured with route aggregation. Route aggregation can be configured multiple times in a region. When the ABR sends route information to other regions, the Sum_net_LSA is generated based on the network segment. If some consecutive CIDR blocks exist in the region, you can use the abr-summary command to aggregate these consecutive CIDR blocks into one CIDR block. In this way, the ABR sends only one aggregated LSA, and all LSA within the range of aggregation network segments specified by this command will no longer be separately sent, this reduces the number of LSDB instances in other regions.

2. Once an aggregation CIDR block of a network is added to a region, all the internal routes of the IP addresses in this region are no longer independently broadcast to other regions, instead, it only broadcasts the route information of the entire aggregation network segment. If the range of the CIDR block is limited by the keyword notadvertise, the route information to the CIDR block will not be broadcast. This CIDR block is described by IP Address/mask. Receiving an aggregation CIDR Block and limiting the CIDR block can reduce the amount of route information exchange between regions. Note: by default, OSPF does not perform intra-region route aggregation.

2. The link is caused by the inability of a region to join area 0, leading to the inaccessibility of some networks. In some regions, the division of area 0 leads to multiple OSPF Autonomous Systems.

1. virtual connection refers to a logical connection channel established between two backbones through a non-backbone area. It can be understood that there is a point-to-point connection between the two backbones, the logical channel refers to the fact that multiple routers running OSPF between two backends only play the role of forwarding packets. Because the destination address of the Protocol packets is not these routers, therefore, these packets are transparent to them. They are only forwarded as common IP packets, and route information is directly transmitted between the two backends. The routing information here refers to the LSA of type3 generated by the ABR. The router synchronization mode in the region has not changed.

2. If physical connectivity cannot be guaranteed due to limitations of the network topology, you can create virtual connections to meet this requirement, virtual Connection refers to a logical connection channel established between two backends through a region that is routed inside a non-backbone area. Both ends of the VBR must be ABR and must be configured at both ends to take effect. The virtual connection is identified by the ID of the Peer router. The region that provides a route entry for both ends of the virtual connection is called the conversion region. Its region number area-id must also be specified during configuration.

3. The virtual connection is activated after it is computed through the route in the conversion area. It forms a point-to-point connection between the two endpoints. Therefore, in this connection, same as physical interfaces, you can configure interface parameters, such as the time interval for sending Hello messages.

Finally, the logical channel refers to the fact that multiple routers running OSPF between two backends only play a role in forwarding packets. Because the destination address of the Protocol packets is not these routers, therefore, these packets are transparent to them. The routing information here refers to the LSA generated by the ABR, and the synchronization mode of the router LSDB in the region has not changed.