OSPF irregular area: a non-backbone area away from the backbone area and a non-contiguous backbone area
Solution
1. Set up a tunnel tunnel, use ordinary GRE to
build a new virtual logical link between legal and illegal ABR-boundary routers using tunnel, and announce the link to ospf
Disadvantages: 1. The actual cycle of ospf It needs to pass through the intermediate link, which greatly increases the resource occupation of the intermediate link.
2. The route selection is not good. The two routes of the ospf device to the same network segment will choose the tunnel link. Pay attention to area ID
two and ospf Virtual link technology The
legal ABR authorizes the illegal ABR to realize route sharing
[r2]ospf 1
[r2-ospf-1]area 1 Enter the traversal area
[r2-ospf-1-area-0.0.0.1]vlink-peer 4.4.4.4 RID of the peer ABR;
advantage: no problem of poor routing.
Disadvantage: the huawei ABR and the peer ABR still affect the intermediate area.
Cisco does not keep alive between the two ABR devices, has no periodic information, and does not Reliable
3. Multi-process two-way redistribution
Multi-process: One device starts different processes in the same area, and one process corresponds to one interface. Each has its own database table, which is not shared with each other. Only the calculated routing table is loaded.
Republish to the same routing table : Use ASBR when different protocols are enabled on different interfaces on the same router—home-made system border routers and protocol border routers
use republishing technology to announce different processes corresponding to different interfaces at illegal ABRs, thereby realizing route sharing The whole network is reachable
[r4]ospf 1
[r4-ospf-1]import-route ospf 2
[r4]ospf 2
[r4-ospf-2]import-route ospf 1
The OSPF protocol uses different types of LSAs to transmit routing or topology information in different environments;
Category propagation range Notifier carries information
1 Router single area, each router in the area is directly connected to the local topology
2 Network single area DR single MA network segment topology
3 summary OSPF domain ABR inter-domain routing (routes in other areas)
4 asbr except The location of the ABR outside the area where the ASBR is located. The area where the ASBR of the
entire OSPF area
is located. The location is notified by type 1. The notifier is the ABR that connects to other areas in the same area as the ASBR.
5 External The area ASBR of the entire OSPF. )
Category link-id Notifier
1 Router The RID of the notifier
2 The interface ip address of each router in the area 2 Network DR The interface ip address of the network segment DR
3 summary Inter-domain routing network number ABR, when passing the next ABR, modify it to the new one ABR
4 ASBR The RID ABR of the ASBR, when passing the next ABR, it is modified to the new ABR
5 External external routing network number ASBR (not changed)