MTU is the same, why can t the OSPF neighbors still get up?

Factors influencing the formation of OSPF neighbors and their solutions.

1. The content of the hello package is inconsistent: the hello package includes: the ID of the originating router, the area ID of the originating router interface, the address mask of the originating router interface, the authentication type and authentication information of the originating router interface, the hello time interval of the originating router interface, the router invalid time interval of the originating router interface, the router priority, the specified router and the backup router, the five marker bits that identify the optional performance, and the router IDs of all valid neighbors of the originating router.

If all the parameters match, then the hello packet is considered valid. Otherwise, the packet will be dropped and the adjacency cannot be established.

2 Different network types cannot establish neighbor relationships.

3 Different hello times and aging times cannot establish neighbors.

4. Neighbors can not be established with different certifications.

5. Neighbors cannot be established for different interface types.

Mask, region, network type (yes Buddha needs to manually refer to neighbors), network segment, is it drother, verification type, hello time, interface is there no sh, is you choosing dr are you too anxious?

Upstairs, how do I join the Tektronix group? Is there a number, can you tell me? Thanks!

Recommend. Tektronix Forum. There are a lot of tech enthusiasts in it.

This is because there is a field in the DD packet that describes the route BAI

During the establishment of the OSPF relationship, the DD packets generated by the DAO at one end will be sent to the neighbor, and the neighbor will check and find that the MTU is inconsistent with the neighbor, so that the neighbor will not continue to interact with the neighbor, so the neighbor's state will always be stuck in the exstart state. It would be nice to change the ends to the same one.

It doesn't matter if the MTU is a little smaller, as long as both ends are the same, it will not affect the final neighbor build, but it may be a little slower (but it is not easy to see).

You're too low, can you put that much information in?

The mtu value is too low, and the 2 ends do not match.

If this interface is set to only accept 1460 packets, and you send him a 1480 packet, how can he receive it?

Check whether the interface status is physically down;

Whether the OSPF process is enabled;

whether the router id is configured to be the same;

whether there is a problem with the segment declaration between neighbors, especially the mask;

whether the MTU values are consistent;

whether the authentication method and key are the same;

whether the hello and dead times correspond to the same;

Whether the network type is broadcast, for example, NBMA needs to be changed accordingly (manually referring to neighbors, changing to broadcast, etc.);

If so, see if there is a problem with the configuration of the special area.

That's probably it, please criticize if it's wrong.

Neighbors cannot be established due to incorrect zone configurations, different hello times, different duplex modes, and NBMA networks.

On the premise of direct connection ping, I mention that the route mask of the network in an area is inconsistent with the plug address mask.

OSPF neighbors can't be established, mainly because:

version is inconsistent;

router id;

The area ID is inconsistent;

The authentication-mode is inconsistent, and the password should not be the same.

NetMask is inconsistent (this requirement is required in broadcast, NBMA networks);

hello dead time is inconsistent;

The n bit and e bit of the option field are inconsistent;

Yes, the default MTU of different manufacturers may be different, and it may need to be modified when the docking is successful, otherwise the neighbor will not be able to establish it.

MTU affects OSPF neighbor discovery.

Common reasons why OSPF neighbor relationships cannot be established:

The interval and dead interval must be the same to establish an adjacency.

2.Area codes are inconsistent.

3.The region types of special regions (such as stub and nssa) do not match.

4.The authentication type and password are inconsistent.

5.The router ID is the same.

Coated acldeny.

7.The MTUs on the link do not match.

8.The OSPF network types under the interface do not match.

I don't need to explain it.

Hello: I think the problem is very simple, there is a problem with the route you declared.

They all chose themselves as DRs, please check the network.