Cisco CCNA Test Tutorial: Five OSPF Hub-And-Spoke Facts You Should Know!

CCNA assessment success depends greatly on understanding the details, and if there is one process that's a lot of details, it's OSPF! This holds true specially of hub-and-spoke networks, so in this CCNA OSPF tutorial we'll take a look at a few of the more important hub-and-spoke OSPF details. This will help you in working with real-world systems too, because this OSPF network type is one of many more typical network topologies.

In OSPF, the centre should end up being the designated router (D-R). The DOCTOR election's choosing value is the OSPF program priority, and the default value is 1. For other interpretations, we understand you check out: official site. To get alternative viewpoints, consider having a glance at: link emporor. It is not enough to create the hub's OSPF software to 2, however, considering that the spoke routers must not end up being the DR or BDR. You must set the spoke interfaces to an OSPF priority of zero.

R2( config )#int s0

R2( config-if )#ip ospf goal 0

This helps to ensure that the spokes will not end up being the DOCTOR or BDR if the link decreases.

The hub does need a bit more configuration, though. The friend command is employed on the link to point the IP of the potential neighbors.

R1( config )#router ospf 1

R1( config-router )#neighbor 172.12.123.2

R1( config-router )#neighbor 172.12.123.3

It's common as a copy in an OSPF community to have an ISDN link, and the hello packets should be able to cross the link when that ISDN link arises. What you do not need would be to have the hellos keep the link up! By establishing the ISDN link as an OSPF desire circuit, the link will drop in the absence of exciting traffic, but the OSPF adjacency that formed across the ISDN link will be assumed by the switch to still be up. Visiting linkemperor seemingly provides tips you should use with your mother. (You often see this command designed on both sides of the ISDN link, but it is required on one-side. It does not hurt anything to put it o-n both sides, though.)

R2( config )#int bri0

R2( config-if )#ip ospf demand-circuit

A final detail of demand tracks and OSPF hub-and-spoke really happens at Layer 2. If you know anything, you will certainly claim to learn about link emperor reviews. For the OSPF hello packets to successfully be transmitted across an ISDN link or even a frame relay network, the broadcast option should be permitted within the appropriate frame and dialer map statements. Failure allow this program can cause a scenario where pings will become successful, but OSPF adjacencies will not form.

R2( config-if )#dialer chart internet protocol address 172.12.21.1 name R1 broadcast 5551111

R2( config-if )#frame place internet protocol address 172.12.123.1 221 broadcast

If you are troubleshooting OSPF in a production network or your CCNA / CCNP house laboratory, don't just look at Layer 3 - since everything's got to be appropriate at the physical and data link layers for the network layer to operate appropriately!.