(open shortest path first, OSPF) expansion configuration

Default RIP and OSPF If the agreement is reissued at two points , Because of their different priorities , So the first one ASBR After the re release of the device , Will affect other ASBR Routing table of the device . So that the route may be returned to the source protocol , Routing feedback occurs ———A Reroute protocol to B After the agreement , It was republished back A agreement . Routing feedback may lead to poor routing and even the emergence of routing loops .
Huawei equipment in order to eliminate the phenomenon of routing feedback , He will be OSPF The priority of internally generated routes is defined as 10, The default priority of routes imported outside the domain is defined as 150.（150 The priority of is higher than that of all Huawei systems IGP Default priority of the protocol ）. In this way, route feedback is eliminated .
Due to the seed metric problem of republishing Technology , Will inevitably lead to poor route selection ; We can only rely on the routing strategy to consider interference in routing .
Control layer flow ： The routing protocol transmits the traffic generated by the routing information
Data layer traffic ： When the device accesses the target network segment , Data traffic generated
Routing strategy ： In the process of controlling the flow of the layer , Intercept flow , Then modify the traffic and forward it or not ; The final implementation affects the generation of router routing table , The effect of interference in route selection .
1, Grab traffic
1．ACL list ——— because ACL The list itself is designed to capture data layer traffic , therefore , Because of the existence of wildcards, it can flexibly match digital features , however , There is no way to match the mask characteristics in the routing information . therefore , He is not good at capturing the traffic of the control layer .
2,IP-prefix--- The prefix list
［r1Jip ip-prefix aa（ Name of the custom prefix list ）permit（ Allow and  
OSPF Extended configuration
1, Manual certification ——— Certification is in OSPF In all packets interacting with neighbors , Carry password . Password is the same. , Then the identity is legal .
OSPF The authentication methods of are divided into 3 Kind of ：
1, Interface authentication —— Configure on the interface of neighbor communication
[r5-GigabitEthernet0/0/0]ospf authentication-mode md5 1 cipher 123456
Be careful ： Configured on both sides keyid It has to be the same , Otherwise, the neighbor relationship authentication will fail .
2, Regional certification ——— Its essence is interface authentication , It is equivalent to configuring interface authentication for all interfaces activated in a certain area at one time .
[r3-ospf-1-area-0.0.0.0]authentication-mode md5 1 cipher 123456
3, Virtual link authentication ——— Add authentication in the virtual link establishment stage . Its essence is also interface authentication .
[r4-ospf-1-area-0.0.0.1]vlink-peer 3.3.3.3 md5 1 cipher 123456 2, Speed up convergence ——— Reduce timer time
modify hello Time
[r5-GigabitEthernet0/0/0]ospf timer hello 5
Be careful ：Hello Time modification , The time of death will automatically follow 4 Match the multiple relationship and modify the time of death
[r1-GigabitEthernet0/0/0Jospf timer dead 20
Be careful ：dead Time modification ,Hello Time does not change automatically
Waiting time--- Waiting for the timer ---DR and BDR Election time at election , Equal to the time of death , Once the time of death is modified , The waiting time will be synchronized
AR2 and AR4 The periodic data between them must pass through the middle area 1, Leading to the middle area
Waste of resources .

The disadvantage of using virtual links to solve irregular areas ：
1, Because of the existence of virtual links ,AR4 and AR2 We need to establish a neighbor relationship , As a result AR2 and AR4 The periodic data between them must pass through the middle area 1, This leads to a waste of resources in the middle area .
2． Only one area can be crossed