CCNA exam success depends largely on knowing the details, and if it is a protocol that is a wealth of detail, it is OSPF! This is particularly the case of hub-and-spoke networks, so that in this CCNA OSPF tutorial we take a look at some of the major hub-and-spoke OSPF details. This will help you to work with the real world and networks, as OSPF network is one of the characteristics of network topologies.
In OSPF, the hub, the designated router (DR). The choice of the DR of the decision is OSPF interface priority, and the default is 1 It is not enough for the Hub of the OSPF interface to 2, said that the router should not be the DR or BDR . She said that the interfaces to an OSPF priority of zero.
R2 (config) # int s0
R2 (config-if) # ip ospf priority 0
This ensures that the rays to the DR or BDR, if the hub is.
The race needs a little more configuration, though. Neighbors of the order must be on the hub to the IP address 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
He is to use an ISDN backup OSPF in a network, and if the ISDN connection, the hello packets must be able on the link. What you do not want is that the link up the hellos! With the configuration of the ISDN connection OSPF demand circuit, the link to deposit the lack of transport, but the proximity OSPF, which is on the ISDN connection is assumed by the router still. (You can see, in general, this command configured on both sides of the ISDN connection, but it is necessary, on a page. It’s not all bad for both sides, but.)
R2 (config) # int bri0
R2 (config-if) # ip ospf demand-circuit
One last detail OSPF hub and spoke circuit and the actual demand is performed on layer 2. For the OSPF hello packets are successful ISDN connection or a frame relay network, the broadcast option must be enabled in part on statements and Dialer map. Otherwise, this option may lead to a situation where a ping is successful, but will not be OSPF adjacencies.
R2 (config-if) # dialer map ip 172.12.21.1 name R1 dissemination 5551111
R2 (config-if) # frame map IP 172.12.123.1 221 items
If you are troubleshooting OSPF in a production network or your CCNA / CCNP home lab, not only on the Layer 3 – because everything has rightly, on the physical and data link layer to layer network is functioning correctly!
