Shulou(Shulou.com)06/02 Report--

OSPF: Open Shortest Path First-Open shortest path first

Support hierarchical design of the network

-region

Backbone: area 0, which is the backbone area.

Non-backbone: not area 0, all called non-backbone areas

All non-zero areas must be directly connected to area 0

It is not possible to communicate directly between non-zero areas.

Configuration commands:

Router ospf 1

Netowrk x.x.x.x y.y.y.y area {id}

Router-id n.n.n.n

Factors affecting OSPF adjacency establishment:

1. Ensure two-way ping communication in the minimum range.

2. Be able to send OSPF messages normally

# ensure that the link is declared properly

3. Able to receive OSPF messages normally

# ensure that the link is declared properly

# make sure ACL releases OSPF traffic

4. Start comparing OSPF message parameters:

1. RID cannot be the same.

Router ospf 1

Router-id x.x.x.x

Clear ip ospf process

2. The region ID must be the same

3. Authentication must be successful (authentication type must be the same and password must be the same)

4. The subnet mask must be the same (in special cases)

5. Hello time must be the same.

Interface fas0/0

Ip ospf hello-interval {value}

6. Dead time must be the same.

Interface fas0/0

Ip ospf dead-interval {value}

7. The special tag bits must be the same

8. Priority must not all be 0 (in special cases)

Interface fas0/0

Ip ospf priority {value}

Layer 9 and layer 3 MTU must be the same, otherwise they will be stuck in Exstart state.

Ineterface f0/0

Ip mtu 1499 defaults to 1500

Mtu: maximum transmission unit max transmit

Debug commands:

Use this command when comparing parameters in hello debug ip ospf hello-- >

Debug ip ospf adj-> use this command when comparing parameters in the OSPF header

Huawei's command to configure OSPF:

[R1] ospf 10 router-id 1.1.1.1

[R1-ospf-10] area 12

[R1-ospf-10-area-0.0.0.12] network 192.168.12.0 0.0.0.255

Verify the command:

Display ospf 10 brief / / similar to show ip protocols

Display ospf 10 peer [brief] / / similar to show ip ospf neighbor

Display ospf 10 lsdb / / similar to show ip ospf database

OSPF adjacency establishment status:

0. Down: neighbors go from intact to hang up

1. Init: initialization, indicating that the local router has received the hello packet sent by the other party.

Attempt: try

This occurs only when OSPF neighbors are established as unicast.

2. Two-way: bi-directional communication status; indicates that the local router has received the hello sent by the other party

Package, and found his own RID (neighbor-list) in the other party's message.

This also shows that the parameters in the hello on both sides have been negotiated successfully.

In a special network environment, we will choose DR/BDR among multiple routers, and the other routers are called DRother. At this point, all routers synchronize the database only with DR/BDR. The relationship between DRother is always in Two-way. The principle of choosing DR: 0, only the router whose priority is not 0 can participate in the election; the router with priority 0 is always called DRother. 1. First, the higher the priority, the better; (the default is 1) 2. If the priority is the same, compare RID, the bigger the better; DR:designated router-designated router BDR:backup designated router-backup designated router

3. Exstart: exchange initialization status; the purpose is to negotiate at this stage to determine

In the subsequent process of database synchronization, how to ensure stable and effective transmission

DBD-database description, database description message

Master/slave

Selection principle: RID, the bigger the better

I-initialization bit, which represents the first DBD message

M-More, indicating that there will be more DBD in the future.

MS-master/slave, which represents the master-slave relationship bit

4. Exchange: exchange

At this stage, what is exchanged is not the specific item content in the database.

Instead, it is the brief information of each LSA entry in the database

The message sent at this time is DBD, which contains

Brief / summary information for LSA

5. Loading: load

In this process, it is the real request and sending of LSA.

The message sent at this time is: LSR/LSU/LSAck

6. Full: adjacency. This status indicates that the databases of both parties are fully synchronized.

OSPF network type:

The working process of OSPF is completely determined by the type of network.

Any type of link corresponds to a network type by default

However, manual modifications can be made based on network requirements

Interface fas0/0 / / modify port network type

Ip ospf network {type}

Show ip ospf interface fas0/0 / / View port network type

Broadcast: broadcast. (MA, multi-access)

When the layer 2 protocol is ethernet, it corresponds to the broadcast network type

Hello is 10sdead is 40s.

Need to elect DR/BDR

Port initiatively sends packets in multicast mode (224.0.0.5AG6)

Non-broadcast: non-broadcast. (NBMA)

When the layer 2 protocol is Frame-relay, the corresponding non-broadcast network type

Hello is 30sDead is 120s

Need to elect DR/BDR

The port does not send packets actively, and the method of sending packets is unicast

[OSPF implements unicast: neighbor x.x.x.x]

Point-to-point: point to point (P2P)

When the layer 2 protocol is HDLC\ PPP, it corresponds to the point-to-point network type

Hello is 10sdead is 40s.

No need to elect DR/BDR

Port initiatively sends packets by multicast (224.0.0.5)

Point-to-Multipoint: point to multipoint (p2mp)

Hello is 30sDead is 120s

No need to elect DR/BDR

Port initiatively sends packets by multicast (224.0.0.5)

Point-to-Multipoint non-broadcast: point to multipoint (p2mp-NB)

Hello is 30sDead is 120s

No need to elect DR/BDR

The port does not send packets actively, and the method of sending packets is unicast

Type of LSA:

OSPF's database contains LSA

OSPF's database organizes LSA in the form of regions.

For all routers in the same area, the database is fully synchronized

LSA summary information details:

Link-id: it represents the name of LSA.

Adv: indicates the name of the router that generated this LSA

Age: indicates the survival time; the maximum survival time is 3600s

Seq: the sequence number represented; every time the link represented by LSA changes, the sequence number of LSA

It will increase by 1.

Checksum: checksum, which is used to ensure that the LSA is not damaged during transmission.

Link-count: link counter, which is available only for type 1 LSA. It means

How many links on the router are declared to have entered the area

Type 1 LSA:router LSA any router will generate a type 1 LSA in any area; type 1 LSA can be understood as "self-introduction" to indicate which links enter the area, which devices are connected, and how they are connected; what is the distance to each other; type 1 LSA can only be transmitted within an area Link-id: the RID adv of the router: the RID transmission range of the router: whether the ADV can only change within an area: there is no change in the type 2 LSA:net Link state. This type of LSA can only be found in the network environment where DR/BDR is elected. Only DR is eligible to produce type 2 LSA. Link-id: indicates the interface IP address of DR; RID of ADV:DR; transmission range: whether the ADV within an area changes: no change; / / based on class 1 LSA or type 1 and 2 LSA in LSDB, you can calculate a route within an area, called O route; type 3 LSA:summary net link state transmits routing information between different areas; this type of LSA, only ABR can be generated. After the three types of LSA are generated by ABR, they first enter into OSPF area 0, and then forward them to other regions. ABR: 1. The "intra-domain-O" route in the non-0 area can be transformed into 3 types of LSA and sent to the 0 area; 2, the "intra-O" route in the 0 area can be transformed into 3 types of LSA and sent to the non-0 area You can also convert the "inter-domain-OIA" route in area 0 into a new type 3 LSA and send it to other non-0 areas; 3. You must not forward type 3 LSA in non-0 area to area 0; link-id: indicates the prefix of the route; RID; transmission range of adv:ABR: whether the ADV within an area changes: yes Type 4 LSA:summary ASB link state is specially created to assist type 5 LSA to calculate routing; the information transmitted is the RID of ASBR; it is generated by ABR in the same area as ASBR; and it changes with each ABR,ADV in the process of transmission. Link-id: indicates the RID; adv:ABR transmission range of ASBR: within the same area; whether the ADV changes: yes; Type 5 LSA:external LSA represents the external routing of OSPF without any area concept; it can be unblocked in the OSPF network. Where there is OSPF, there are five types of LSA. Link-id: indicates external routing prefix; RID of adv:ASBR; transmission scope: no limit; whether ADV changes: no; Note: when calculating intra-domain routes, Class 1 or Class 1 and Class 2 LSA; are used to calculate inter-domain routes, using Class 3 and Class 1; when calculating external routes, use Class 5 and 1, or Class 5, 4 and 1 -non-0 area is not directly interconnected with area 0. Solution: 1. Introduce external routes; # run multiple OSPF processes and redistribute each other 2. Introduce internal route (O IA) # and introduce virtual link. OSPF neighbor relationships established through virtual links always belong to area 0; R3; router ospf 1 area 12 virtual-link 4.4.4.4 R4: router ospf 1 area 12 virtual-link 3.3.3.3Virtual-link: virtual links

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