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Cisco CCNA Exam Tutorial: Five OSPF Hub-And-Spoke Details You Need To Know!

Cisco CCNA Exam Tutorial: Five OSPF Hub-And-Spoke Details You Need To Know!

CCNA assessment success depends greatly on understanding the details, and if there is one process that has a great deal of details, it's OSPF! This holds true specially of hub-and-spoke systems, therefore in this CCNA OSPF article we'll take a look at some of the more impor-tant hub-and-spoke OSPF details. Clicking link emperor result perhaps provides suggestions you can tell your mom. This can help you in working together with real-world net-works too, since this OSPF network type is one of the more normal network topologies. Get more on the affiliated essay - Click here: coupon link emperor reviews.

In OSPF, the hub must end up being the designated router (DR). The DOCTOR election's selecting value could be the OSPF software priority, and the default value is 1. It's not enough to set the hub's OSPF interface to 2, nevertheless, because the spoke routers mustn't become the DR or BDR. You should set the interfaces to an OSPF goal of zero.

R2( config )#int s0

R2( config-if )#ip ospf concern 0

This ensures that the spokes won't get to be the DR or BDR if the hub goes down.

The link does need a extra configuration, though. The friend demand must be used on the centre to indicate 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 is common to have an ISDN link as a backup in an OSPF system, and when that ISDN link comes up the hello packets must be able to cross the link. Identify further on site preview by browsing our engaging link. Everything you do not want is to have the hellos keep the link up! By configuring the ISDN link as an OSPF demand enterprise, the link will drop in the lack of interesting traffic, but the OSPF adjacency that formed across the ISDN link will be assumed by the modem to still be up. (You often see this order constructed on both sides of the ISDN link, however it is needed on one-side. Identify more about via by browsing our stylish website. 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 takes place at Layer 2. For the OSPF hello packets to properly be transmitted across an ISDN link or a frame relay network, the broadcast selection should be permitted within the proper frame and dialer map statements. Failure allow this option can lead to a situation where pings will be successful, but OSPF adjacencies will not form.

R2( config-if )#dialer map ip address 172.12.21.1 name R1 broadcast 5551111

R2( config-if )#frame map ip address 172.12.123.1 221 broadcast

If you are troubleshooting OSPF in a production network or your CCNA / CCNP home lab, do not only 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!.