While you construct a routed community utilizing OSPF as your routing protocol of alternative it’s a must to think about the truth that OSPF will robotically detect the Layer 2 encapsulation sort and undertake one in every of 6 methods to function on that hyperlink.This Broadcast mode is the default state that OSPF will set an interface to when OSPF detects the encapsulation sort being Ethernet and can think about this media as broadcast mediaIf you activate OSPF over a Body-Relay community and had been to vary the community sort to “broadcast” then it might be smart to construct the community as full mesh community the place there are PVCs to one another web site.If the Body Relay community is specified by a partial mesh and the bodily topology doesn’t present the multi entry that OSPF believes is on the market then there perhaps an issue with reachability
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 grow to be a problem as a result of the DR and BDR must have full bodily connectivity with all different OSPF routers that exist within the Broadcast community.You probably 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 think about themselves as a part of the election course of. To do that it’s essential to configure the spokes with the next command: (Assuming we’re utilizing the bodily interface)Router(conf)#interface serial zero/1/0Router(conf-if)#ip ospf precedence 0On the Hub router to be on the protected facet set the next command so that it’ll grow to be the DR. (Assuming we’re utilizing the bodily interface)Router(conf)#interface serial zero/1/0Router(conf-if)#ip ospf precedence 255OSPF will ship Multicast visitors over the Broadcast media and attributable to this you’ll not must configure the DR with ant (And BDR when you’ve got one)static record of all different routers. In Broadcast mode all neighbours are dynamically found with OSPF messages being despatched to the multicast tackle of 224.zero.zero.5
Additionally OSPF is not going to change the interface timers from the default 10 second Whats up and 40 Useless Timer.One other level to keep in mind relating to Working OSPF in Broadcast mode in a Hub and Spoke community is that the spoke being the DR won’t ever change the Ip tackle of the following hop will the DR change the price worth, the problem right here being that if one spoke must ship knowledge to the opposite spoke the following hop tackle will likely be unreachable except you manually specify a frame-relay map to a neighborhood DLCI