[Huawei] OSPF router ID election, role, and conflict

[Huawei] OSPF router ID election, role, and conflict
1. OSPF Router ID election Rule a) If routerID is set by command, select this as ROUTER IDb) If routerID is not set by command, if loopback address exists, select the largest loopback address as the router ID. If no loopback address exists, select the largest address in other interfaces as the router ID. 2. Refresh Rule a for OSPF router ID. Only when the address of the interface elected as routerID is deleted or modified will the election process be triggered, this process takes effect only when the reset OSPF process is enabled. B) The selected interface status changes, and a larger loopback or other interface addresses are configured, will not cause the router id to be re-elected. c) the router ID cannot be 0.0.0.0, 255.255.255.2553, or routerid. a) act as the unique identifier of the router in the OSPF region. B) in DR and BDR election, when the priority is the same, the election for a large router ID is DR. 4. router ID conflict problem 1) topology, see appendix 2) scenario 1: Both R1 and R2 are in area0, r1/R2 has the same routerID [R1] ospf1 rof1-id 2.2.2.2 area 0.0.0.0 network 10.1.1.1 0.0.0.0 network 10.1.12.1 0.0.0.0 [R2] ospf1 rof1-id 2.2.2.2 area 0.0.0.0 network 255.0.0.0.0 network 10.2.2 1.0.0.0.0: r1 and R2 cannot establish OSPF neighbor relationship. Analysis: After R1 sends the hello packet, R2 receives the hello packet from R1 and finds that the routerID is consistent with its own router ID, and the neighbor cannot be established. 3) Scenario 2: R1, R2, and R3 are in area0, r2 and R3 have the same routerID [R1] ospf1 rof1-id 1.1.1.1 area 0.0.0.0 network 10.1.1.1 0.0.0.0 network 10.1.12.1 0.0.0.0 network 255.0.0.0.0 [R2] ospf1 router-id 2.2.2.2 area 0.0.0.0 network 10.1.12.2 0.0.0.0 10.1.2.2 0.0.0.0 [R3] ospf1 rof1-id 2.2.2.2 area 0.0.0.0 network 10.1.3.3 0.0.0.0 network 10.1.13.3 0.0.0.0 result: a) R1, R3, R1, and R2 can establish OSPF neighbors respectively. B) R2 can learn R1 or R3 routes, but the routes are constantly jitters, Learn R3 later; c) R1 and R3 cannot learn routes from each other. Analysis: a) OSPF identifies LSA with {type, ls id, and advrouter}, and identifies an LSA instance with (age, seq num, and checksum); B) LSA sent by R3, r1 flood, R2 receives the LSA; c) R2 checks the LSA received, and finds that {type, ls id, and adv router} are consistent with their own, and they are considered to be their own LSA; e) R2 comparison (age, seq num, checksum). If it is found that the LSA is updated than the database in which it is stored, seq num + 1 is returned to LSA. F) When R1 receives the LSA of R2, it finds that {type, ls id, adv router} is consistent with R3 of its own database and is considered to be an LSA; then compare (age, seq num, checksum), and find that seqnum is larger, LSA is newer, then flooding. G) R3 receives the LSA of R2 forwarded by R1, which is the same as that of {type, ls id, advrouter}. (age, seq num, checksum) is updated, which is equal to that of R2. H) LSA is continuously transmitted between R3, R1, and R2. Therefore, R1 learns the route of R3 later and the route of R1 later. Routes cannot be learned from each other between R1 and R3. The Huawei simulator experiment shows that R1/R3 will re-elect a routerID to initiate the OSPF neighbor creation process. After the neighbor is established, R1 can learn the routes of R2 and R3. 4) scenario 3: R1 and R2 are area0 and R4 are area1, r1 and R4 have the same routerID [R1] ospf1 rof1-id 1.1.1.1 area 0.0.0.0 network 10.1.1.1 0.0.0.0 network 10.1.12.1 0.0.0.0 network 255.0.0.0.0 [R2] ospf1 router-id 2.2.2.2 area 0.0.0.0 network 10.1.12.2 0.0.0.0 10.1.2.2 0.0.0.0 area 0.0.0.1 network 10.1.24.2 0.0.0.0 [R4] ospf1 router-id 1.1.1.1 area 0.0.0.1 network 10.1.4.4 0.0.0.0 network 10.1.24.4 0.0.0.0 result: a) area0, R1 can be created with R2 Establish a neighbor relationship; B) area1, R1 can establish a neighbor relationship with R4. C) R1 and R4 can learn routes from each other. Analysis: a) When R1 sends an LSA, R2 sends three types of LSA to area1: router IDb Whose ls id is the route prefix, R2 is the ABR, and adv router is the R2) when R4 receives three types of LSA, it finds that it is a new router id. Unlike itself, it is included in LSDB and submits the route table. C) routes can be learned when the LSA sent by R4, R2 and R1 are the same.