A: OSPF Open Shortest Path First Chinese link-state routing protocol machine
he belongs dynamic IGP protocol for medium-sized networks. Can BFD for periodically by sending a neighbor hello packet, to run multiple OSPF routing process in a router, in order to reduce the number of LSA AS can be divided into a plurality of different Area, within a region of preferably not More than 50 routers, routing information interaction through LSA packets, five kinds of sub-packets, are: hello, dbd link state database, LSR, LSU.LSACK. We were established neighbors and adjacencies.
Each router in an AS ID must be unique, but different processes with a router in the router ID can be the same.
According to OSPF agreement, all other areas must be connected to the backbone area. FIG follows:
two: Type LSA
LSA is used to exchange link state information to know the whole network topology, and route calculated independently.
The first LSA: Router LSA (router LSA) each router generates the LSA OSPF router,
the second type LSA: Network LSA (network LSA) is generated by the DR (designated router) or the BDR (Backup Designated Router), only in the region within the spread, there is only a broadcast type network.
The third LSA: polymeric network LSA (network summary LSA) Network Summary LSA, generated by ABR.
The fourth category LSA: ASBR polymerization LSA (ASBR summary LSA) is generated by ABR.
Fifth category LSA: AS external LSA (Autonomous systeam external LSA) is generated by ASBR.
Category VII LSA: NSSA external LSA (NSSA External LSA) also generated by ASBR.
Three: OSPF network type support
1, broadcast and broadcast
2, NBMA (Non-broadcast multi -access) type when the link layer protocol is Frame Relay, X.25, OSPF defaults to NBMA. Transmitting unicast hello packets, DD packets, LSR, LSU.LSACK packet
3, multipoint P2MP hello packet in multicast mode (224.0.0.5), DD send unicast packets, LSR , LSU.LSACK packet
4, point (point-to-point) P2P when the link layer protocol is PPP, HDLC, LAPB, OSPF defaults network type P2P. In the network, multicast (224.0.0.5) sending OSPF packets.
Four: OSPF protocol header format
There are five main: hello packets, DD (database Description, database description), LSR (linkstate request, link state request), LSU (linkstate update link state updates) and LSack (Linkstate acknowledgment chain Road state response) message.
Five: OSPF works
. 1, OSPF state machine
OSPF total of eight kinds of state machines, namely: down (initial state), attempt (only occurs in the NBMA network), init, 2-way (election DR and the BDR, the region DR and BDR routers only interact with the LSA, before DROther do not need to interact and DR election is complete, no role preemption), exstart, exchange (interactive DD packets and determine the master-slave relationship), loading (sending LSR, LSDB update request, sending and answer LSU), full (to establish two-way adjacency).
Among the entire OSPF adjacency relationship building equipment is divided into: neighbor discovery, master-slave relationship established stage, database synchronization stage, fully adjacent stage.
六：OSPF基本命令
SYS
Enter system view, return user view with Ctrl+Z.
[Huawei]ospf 100
[Huawei-ospf-100]area 0
[Huawei-ospf-100-area-0.0.0.0]network 192.168.1.0 0.0.0.255
[Huawei]interface GigabitEthernet0/0/0
[Huawei-GigabitEthernet0/0/0]ospf en
[Huawei-GigabitEthernet0/0/0]ospf enable 1 ar
[Huawei-GigabitEthernet0/0/0]ospf enable 1 area 0
虚连接
[Huawei]ospf 100
[Huawei-ospf-100]area 2
[Huawei-ospf-100-area-0.0.0.2]vlink-peer 1.1.1.1
[Huawei]ospf router-id 1.1.1.1
[Huawei-ospf-1]are
[Huawei-ospf-1]area 0
[Huawei-ospf-1-area-0.0.0.0]network 192.168.0.0 0.0.0.255
