ospf on NBMA enviroment

[swapan.samanta89]

Quoted from jeff doyle book TCP/IP vol-1 "on point-to-point networks,updates are sent multicast address AllSPFRouters(224.0.0.5).On point-to-multipoint and virtual link networks,updates are unicasted to the interface addresses  of the adjacent neighbors"

But,point-to-point and point-to-multipoint bot network types support i)dynamic neighbor discovery ii)no DR and BDR elections occur

then why one update are sent multicast and other are sent unicast....

regards

swapan

[Reza Sharifi]

Have a look at this document and look under Point-to-Multipoint non-broadcast Network section

https://ccieblog.co.uk/ospf/ospf-hello-protocol

HTH

[swapan.samanta89]

hello reza,thank u for your reply.TCP/IP VOL1 by jeff doyle books(page364 ospfv2) mentions that "On point-to-point networks,update are sent to the multicast address ALLSPFrouters(224.0.0.5)".

My point of view.on point-to-point network,there is no DR and BDR election.then it should be unicast.

please clear my confusion....

[dmuinoorallo]

Hello ,

OSPF only use unicast in networks in wich your router don't know your neighbours, for example frame relay.

In this networks you need configure your neighbours, because don't have broadcast packet.

Unicast or broadcast is for type of network, not if theres DR/BDR or not.

[dmuinoorallo]

OSPF use unicast when type of network don't support broadcast like:

• Point-multipoint non broadcast network
• Non broadcast network