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OSPF Network Types – Non Broadcast
OSPF Community Varieties: Non-Broadcast Multicast
While you construct a routed community utilizing OSPF as your routing protocol of alternative you must consider the truth that OSPF will routinely detect the Layer 2 encapsulation kind and undertake considered one of 6 methods to function on that hyperlink.
The primary of those 6 behaviours which we are going to cowl is OSPF Non-Broadcast mode
This Non-Broadcast mode is the default state that OSPF will set an interface to whenever you execute the command “encapsulation frame-relay” on a serial interface.
OSPF will contemplate this media like every other broadcast media akin to Ethernet.
NBMA clouds are often in-built a hub and spoke topology. PVCs are specified by a partial mesh and the bodily topology doesn’t present the multi entry that OSPF believes is on the market.
OSPF on this mode will try to additionally elect a Designated Router and a Again Designated router. The collection of the DR and BDR the can turn out to be a difficulty as a result of the DR and BDR must have full bodily connectivity with all different OSPF routers that exist within the Non-Broadcast community. In case you have a hub and spoke community had been one router has Body Relay PVC’s to every spoke then logically you’ll configure the Hub to be the DR and the spokes to not contemplate themselves as a part of the election course of. To do that you have to configure the spokes with the next command: (Assuming we’re utilizing the bodily interface)
interface serial 0
ip ospf precedence 0
On the Hub router to be on the secure aspect set the next command so that it’s going to turn out to be the DR. (Assuming we’re utilizing the bodily interface)
interface serial 0
ip ospf precedence 255
OSPF won’t ship any Multicast site visitors over the Non-Broadcast media and as a result of this you have to to configure the DR with (And BDR you probably have one)a static listing of all different routers connected to the Non-Broadcast community, within the instance beneath our neighbors are 10.1.1.2 and 10.1.1.3.
To do that you have to to make use of the next command:
router ospf 1
neighbor 10.1.1.2 10
neighbor 10.1.1.3 10
The “poll-interval” is the period of time an NBMA interface waits earlier than polling (sending a Howdy) to a presumably useless neighbor. The neighbor command applies to routers with a possible of being DRs or BDRs (interface precedence not equal to 0).
Additionally OSPF will change the interface timers to 30 second Howdy and 120 Lifeless Timer.