OSPF Interview Questions & Answer Part-4 | OSPF Network Types
Summary Insights:
- There is a big confusion for all Networks engineer that actually how many OSPF Network types.
- In some books & blogs you will see five then other will show four types. Let me clarify this today.
- The main open standard for all vendors OSPF Network types are three. Other two are cisco proprietary.
Main OSPF Network Types:
- Point to Point
- Broadcast
- Non Broadcast
Cisco Proprietary OSPF Network Types:
- Point to Multipoint
- Point to Multipoint Non Broadcast
Questions:
- How many OSPF Network Types?
- OSPF Peer is up but not sharing Routes, What’s the reason?
- What is different b/w Point to point & Point to multipoint non broadcast?
- Why Next hop IP is changing in Point to multipoint Network Type?
- Hello & dead interval in Non Broadcast multi access?
- Why hello & dead timer default is changed in Point to multipoint Network type?
- What is neighbor command used for?
- In which Network type manual neighbor need to configure?
- Why No DR/BDR in point to multipoint Network type?
Next let me explain that why OSPF using these types of Network & in which scenario we will use which one?
Further advantage & disadvantage of each Network Types & multi vendor’s configurations Example.
Why Need OSPF Network Types:
The Best Network Designer & Network Engineer is that to think about efficient utilization of
Network resources, Redundancy, Security & enables the feature to achieve best result of Devices. To get above things different Network types is used in different scenarios.
OSPF algorithm will react differently on different Network types. Like hello & dead interval times,link Bandwidth & fewer chances from attacker.
Point to Point:
In point to point OSPF Network type the two points or Devices are connected with each other. If one side sends packets it will receive only one remote side node. Default point to point Network type for the serial port directly connected two devices.
Key Points:
- The configurations is simple
- Using multicast mode
- No DR/BDR election
- Lease line connectivity is expensive
- No backup if link is down
- Hello & dead interval is 10 sec & 40 sec.
Broadcast:
In broadcast Network type multiple devices are connected through same subnet,
for example 5 routers connected through switch. Default Network type of Ethernet media is Broadcast.
Key Points:
- Configurations is simple
- Using multicast mode
- DR & BDR election
- Easy to attack
- Hello timer is 10 sec & dead interval is 40 second.
Non Broadcast:
As multi access Network like Frame relay & ATM not support Broadcast. We can connect multiple devices but it will be point to point not broadcast. This type is Non-Broadcast.
In this separate packet will be send to each node so bandwidth utilization will be
high & must know the peer devices.
Key Points:
- Uses unicast mode for each peer node
- DR/BDR Election
- Its secure than Broadcast Network type
- Configuration is complex as manual
- Hello & dead interval is 30 sec & 120 sec respectively.
Point to Multipoint:
It is chunk/combination of Point to Point connectivity. When multiple routers communicate with only one router like hub spoke scenario. Using multicast mode to detect neighbors.
Key Points:
- No DR/BDR Election
- Using multicast mode 224.0.0.5
- Non Multi-vendor scenario
- Less complex
- Hello & Dead interval is 30s & 120s
Point to Multipoint Non Broadcast:
This is same like point to multipoint but with Non Broadcast feature like manual neighbor configurations as in point to multi point is automatic.
Key Points:
- No DR/BDR Election
- Hello & Dead interval is 30s & 120s
- Using unicast mode
Now let me summarize all Network types with one comparison table it will help you
during implementation of different scenarios.
