Tip: Router OSPF experience

Welcome to the network technology community forum, and interact with 2 million technical staff. We recently called an ATM.

Welcome to the network technology community forum, and interact with 2 million technical staff> recently, an ATM-Frame Relay Network was called, and OSPF was used in the middle to create a domain, which was originally EASY, but the route is always unavailable. sh ip ospf nei, and it is found that NEI cannot be FULL. Check the configuration. After debugging, it turns out to be the MTU of the atm frame-RELAY packet.

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I recently called an ATM-Frame Relay Network and used OSPF in the middle to create a domain. I thought it was very EASY, but the route was always unavailable. SH IP OSPF NEI, it is found that NEI cannot be FULL. Check the configuration. If DEBUG is used, the MTU value of the original atm frame-RELAY packet is different. Set it to the same value.

OSPF supports non-class IP addresses, so it is often used. 192/. 252. In this way, it is easy to produce errors when writing back code.

1. Note that the anti-code of the subnet mask must be written

2. Note that OSPF routing can be added only when all ports are connected.

3. the area must be the same

4. Note that the hello and dead time must match the two ends.

Basic OSPF operations

1. The connected router must be a neighbor (exchange by sending Hello Packet );

2. Build an adjacent relationship

(1) Not all neighbors will build an adjacent relationship. Generally, there is a duty router, and other routers will build an adjacent relationship with it;

(2) once the adjacent relationship is established, the LSA (link state Declaration) is sent to the adjacent router.

3. Send LSA between neighboring routers;

4. Accept LSA;

5. Build a database with the same topology (link status );

6. Use the Shortest Path First method to calculate the shortest path;

7. Create a route table.

OSPF operations in Broadcast Networks

1. The connected router must be a neighbor

1. Send Hello Packet at a certain Interval (Hello Interval) through the Hello protocol (in the broadcast network, the Interval is 10 seconds.

2. The destination address of Hello Packet is 224.0.0.5 (representing all OSPF routers );

3. Hello Packet parameters:

(1) Router ID: Router ID (identified by IP address );

A. Select the highest interface IP address to identify yourself;

B. When there is a Loopback interface, select the IP address of the highest Loopback interface as the Router ID;

C. We recommend that you create a Loopback interface in the OSPF Router and use the IP Address as the Router ID of the Router.

(2) Area ID;

A. to identify the location of the router;

B. Only routers in the same region (with the same Area ID) can build neighbors;

(3) Hello Interval is 10 seconds;

(4) Dead Interval is 4 * Hello Interval = 40 sec

(5) Verify the password;

(6) Stub Area Flag end Area sign.

2. Build an adjacent relationship

1. Select a DR (Duty router) through Hello Packet );

(1) first check the priority of the interface;

(2) When the priority is the same, select the Router with the highest Router ID as the DR.

2. Select a BDR (Backup duty router)

If the DR is down, the BDR will become the DR, and then re-select the BDR.

3. Non-DR and BDR Router are Other Routers.

How do DR, BDR, and Other Routers establish the adjacent relationship:

DR-other ?? DR;

DR-other ?? BDR;

DR ?? BDR.

OSPF operations in Broadcast Networks

1. The connected router must be a neighbor

1. Send Hello Packet at a certain Interval (Hello Interval) through the Hello protocol (in the broadcast network, the Interval is 10 seconds.

2. The destination address of Hello Packet is 224.0.0.5 (representing all OSPF routers );

3. Hello Packet parameters:

(1) Router ID: Router ID (identified by IP address );

A. Select the highest interface IP address to identify yourself;

B. When there is a Loopback interface, select the IP address of the highest Loopback interface as the Router ID;

C. We recommend that you create a Loopback interface in the OSPF Router and use the IP Address as the Router ID of the Router.

(2) Area ID;

A. to identify the location of the router;

B. Only routers in the same region (with the same Area ID) can build neighbors;

(3) Hello Interval is 10 seconds;

(4) Dead Interval is 4 * Hello Interval = 40 sec

(5) Verify the password;

(6) Stub Area Flag end Area sign.

2. Build an adjacent relationship

1. Select a DR (Duty router) through Hello Packet );

(1) first check the priority of the interface;

(2) When the priority is the same, select the Router with the highest Router ID as the DR.

2. Select a BDR (Backup duty router)

If the DR is down, the BDR will become the DR, and then re-select the BDR.

3. Non-DR and BDR Router are Other Routers.

How do DR, BDR, and Other Routers establish the adjacent relationship:

DR-other ?? DR;

DR-other ?? BDR;

DR ?? BDR.