Combination of two swords-ospf Virtual links and route Aggregation

Route Aggregation
Route aggregation combines multiple routes into a single route, which is usually implemented on the ABR. It is a technology that organizes network layer IP addresses in a hierarchical manner, so that addresses have "topological importance.
Route aggregation method
1. Inter-area route AggregationInter-area routes are aggregated on the ABR to act on routes from the. It does not work for external routes introduced by route redistribution. To use the Routing aggregation feature, the network addresses in a region should be continuous. These block addresses can form a range.
2 External route AggregationExternal route aggregation refers to introducing the External route into the OSPF area through route redistribution. Similarly, make sure that the range of the External route to be aggregated is continuous. If the routes aggregated from two different routers contain the same part, an error occurs when the packets are forwarded to the destination address.
OSPF Virtual Link
Virtual Connection refers to a logical connection channel established between two backends through a non-backbone region (transition region-Transit Area, it can be understood that there is a point-to-point connection between the two APRs. 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 and only forwarded as common IP packets.) the routing 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.
The above information is from the Internet. Are you confused when you see the above explanation. Don't worry. Next I will use an experiment with a picture of the truth to help you understand this.
Tutorial topology:

Lab device:
3 Huawei routers R2621
1 Huawei switch S3526
Tutorial steps:
1. Configure vror1 r1
Configure IP addresses on ports s0 and s1


Enable the ospf routing protocol and enter ports s0 and s1 to enable ospf release.


Reset ports s0 and s1



2. Configure on vror2 r2
Configure IP addresses on Port 1-8 of loopback






Configure the IP address on port s0 and reset it.




Enable the ospf routing protocol and access ports s1 and loopback 1-8 to enable ospf. Release


3. Configure vror3 r3
Configure IP addresses on ports E1 and S1

Reset s1 and E1



Enable ospf and open ports s1 and E 1 to enable ospf. Release

Although the primary region is required here, ignore it.
4. Enter S4 for configuration
Add E0/24 to vlan 10 and assign vlan 10 addresses


Configure the IP address of Loopback1

Enable ospf and publish relevant network segments

5. view the route table
View route tables of routers R1, R2, R3, and S4




From the preceding route table, we can see that the virtual link is not enabled, so the Routes learned by the routers are incomplete. Further configuration is required.
Further configure the virtual link on R1
On R1, You can first view the id of the neighbor router and then configure it further.

Further configure the virtual link on R1
On R1, You can first view the id of the neighbor router and then configure it further.



6. view the route table again
View the route table of vror2 R2. You can see that R2 has learned the complete route.


View the S4 route table and find that S4 has learned

7. Configure route Summary
By viewing the preceding route table, you can find that there are too many route entries, and configuring route summary can solve this problem.
The route configuration is generally configured on the ABR.
Configure the ABR summary on R1


View the route table on S4 and find that the summarized route has been learned.

Author: pheonix blog