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

CCNA test success depends greatly on understanding the details, and if there is one process that's a great deal of details, it's OSPF! This holds true particularly of hub-and-spoke networks, so in this CCNA OSPF article we'll have a look at a few of the more important hub-and-spoke OSPF details. If you have an opinion about irony, you will possibly wish to research about linkemporer article. This can help you in working together with real-world net-works also, because this OSPF network type is one of the more common network topologies. Clicking review link emperor possibly provides aids you could give to your aunt.

In OSPF, the centre must end up being the designated router (DR). The DOCTOR election's choosing value will be the OSPF screen priority, and the default value is 1. It's not enough to create the hub's OSPF program to 2, but, considering that the spoke routers mustn't get to be the DR or BDR. You need to set the 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 won't become the D-R or BDR if the center falls.

The center does require a bit more configuration, although. Discover more about follow us on twitter by browsing our unusual encyclopedia. The friend control can be used on the heart to point the IP-ADDRESS of the possible 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 to have an ISDN link as a copy in a OSPF community, and when that ISDN link comes up the hello packets should be able to cross the link. That which you do not need would be to have the hellos keep the link up! By making the ISDN link being an OSPF desire circuit, the link will drop in the absence of interesting traffic, but the OSPF adjacency that formed across the ISDN link will be assumed by the hub to still be up. (You often see this order configured on both sides of the ISDN link, but it is just needed on one side. It does not hurt anything to place it on both sides, though.)

R2( config )#int bri0

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

One last aspect of demand circuits and OSPF hub-and-spoke really occurs at Layer 2. For the OSPF hello packets to properly be transmitted across an ISDN link or a frame relay network, the broadcast selection has to be permitted within the proper frame and dialer map statements. Failure allow this option can cause a scenario where pings will be successful, but OSPF adjacencies won't form. To check up additional info, please gaze at: the guide to link emperor.

R2( config-if )#dialer place ip address 172.12.21.1 title R1 broadcast 5551111

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

When you're 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 in order for the network layer to function properly!.