Configuring OSPF Over Non-Broadcast Multiaccess Networks (NBMA)

All community communication occurs utilizing the usual OSI framework. At every layer a set of protocols work which standardize the necessities of communication and put together information which is universally acceptable to the following layer. Of community communication an important side is information packet routing – there are a number of protocols accessible to help routing similar to TCP/IP, OSPF and many others. The one which provides the optimum route from supply to vacation spot is ideally thought of for communication over massive heterogeneous networks.

In at this time’s article we are going to look extra intimately about how OSPF (Open Shortest Path First) hyperlink state routing protocols work over non broadcast networks (NBMA), the way to configure OSPF over NBMA, its options and limitations. 

OSPF Over Non-Broadcast Networks (NBMA) 

OSPF is a hyperlink state routing protocol (used largely broadly) which makes use of details about the state of community hyperlinks to establish or decide one of the best path for information packets. There are three varieties of community varieties in OSPF which decide how OSPF will route information packets throughout networks.

• Broadcast
• Level-to-Level 
• No Broadcast 

Along with above there are two extra Cisco proprietary community varieties 

• Level to Multipoint
• Level to Multipoint Non broadcast 

Because the level of focus on this article is No Broadcast networks (NBMA), we are going to go deeper into this. Non broadcast OSPF networks utilized in point-to-point hyperlinks the place a number of OSPF routers are linked similar to body relay, X.25, ATM digital circuits (not used these days). For all hosts in a single NBMA community, information is distributed from one host to a different with out broadcasting info throughout all hosts. Switched networks or digital circuits present direct routing of information packets. NMBA communicates on to different hosts however on the identical bodily hyperlink different hosts can’t hook up with it. NBMA makes use of subsequent hop decision protocol (NHRP) to search out routes routinely by way of the community 

Configure OSPF Over Non-Broadcast Networks (NBMA) 

Non broadcast Multiaccess (NBMA) broadcast mannequin based mostly on choice of designated router (DR) and a backup designated router (BDR). There are two methods to deploy this: defining the community sort as broadcast with the IP OSPF community broadcast interface sub command or configure the neighbor statements utilizing router OSPF command. 

1. Configuration for NBMA (use Community Sort Broadcast)

Router 1 Configuration 

Router 2 Configuration 

2. Configuration for NBMA (use Neighbour statements) 

Router 1 Configuration

Router 2 Configuration

OSPF Non-broadcast Community Options 

• Community can join greater than two routers however by default they can’t broadcast
• Multipoint body relay interfaces are default community sort for OSPF 
• OSPF routers on NBMA networks select a DR (Designated router) and a BDR (backup designated router), all OSPF packets are unicast between every neighbor specified with ‘neighbor’ command
• The following hop IP don’t change and stays identical as IP handle of the router which despatched the packet
• The assigned precedence by default is ‘1’ and must be set to = 0 (turned off) on ALL SPOKES to cease spoke from changing into a blackhole DR/BDR
• 30 seconds is Whats up interval and 120 seconds is lifeless interval in OSPF 

Professionals & Cons of OSPF over NBMA

PROS

• Simpler to regulate site visitors movement on community and in addition useful to restrict quantity of site visitors goes by way of a selected hyperlink
• Non broadcast community varieties are safe since hackers can simply intercept broadcast which is not going to occur right here

CONS

• Tough to configure because it requires guide neighbor configuration
• Tough to scale on OPSF networks as in comparison with different community varieties
• Restricted characteristic availability of OSPF options when this community sort is used
• Vulnerable to sure varieties of faults 

Proceed Studying:

OSPF Neighbor States Defined

OSPFv2 vs OSPFv3: Detailed Comparability