Cisco CCNA Assessment Tutorial: Five OSPF Hub-And-Spoke Facts You Should Know
CCNA assessment success depends greatly o-n knowing the details, and if there is one process that has lots of details, it"s OSPF! This is true especially of hub-and-spoke systems, so in this CCNA OSPF guide we"ll take a look at several of the more impor-tant hub-and-spoke OSPF details. This will help you in working with real-world networks as-well, since this OSPF network type is one of many more normal network topologies.
In OSPF, the center should end up being the designated router (DOCTOR). Visiting link emporor maybe provides suggestions you should use with your friend. The DOCTOR election"s choosing value could be the OSPF software goal, and the default value is 1. It is not enough to set the hub"s OSPF program to 2, nevertheless, since the spoke routers mustn"t end up being the DR or BDR. You should set the mention interfaces to an OSPF priority of zero.
R2( config )#int s0
R2( config-if )#ip ospf priority 0
This means that the spokes won"t end up being the DOCTOR or BDR when the heart goes down.
The centre does need a extra configuration, though. The friend demand can be used on the hub to indicate the INTERNET protocol address of the potential neighbors. Browse here at the link http://linkemperor.com to compare how to provide for this concept.
R1( config )#router ospf 1
R1( config-router )#neighbor 172.12.123.2
R1( config-router )#neighbor 172.12.123.3
It is common as a copy within an OSPF community to have an ISDN link, and when that ISDN link arises the hello packets should be in a position to cross the link. Everything you don"t want would be to possess the hellos keep the link up! By making the ISDN link as an OSPF need enterprise, the link will drop-in the absence of exciting traffic, but the OSPF adjacency that produced across the ISDN link will be thought by the router to still be up. (You usually see this control constructed on both sides of the ISDN link, however it is needed 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
Your final detail of need circuits and OSPF hub-and-spoke really takes place at Layer 2. For the OSPF hello packets to effectively be transmitted across an ISDN link or even a frame relay network, the broadcast option must be enabled within the proper frame and dialer map statements. We found out about linkemporor by searching Google. Failure make it possible for this program can result in a scenario where pings will become successful, but OSPF adjacencies won"t form.
R2( config-if )#dialer chart ip address 172.12.21.1 name R1 broadcast 5551111
R2( config-if )#frame place ip 172.12.123.1 221 broadcast
When you are troubleshooting OSPF in a manufacturing network or your CCNA / CCNP home laboratory, don"t just look at Layer 3 - because everything"s got to be right at the physical and data link layers in order for the network level to function effectively!.
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