Study Session Number 9! Notes from OSPF lab practice! Exam Objs! #10

Hi Everyone, 

These are some notes I've taken for myself from doing Neil Anderson's OSPF lab, the things have been discussed in my previous blogs but I'm just writing these down for my own memory purposes - hopefully doing this will also reinforce the muscle memory of it all, can't believe theirs so much to OSPF but I love it! 

Remember the router id (also referred to as Neighbor ID) in ospf is a device identifier it is NOT an interface IP address.

Process numbers do NOT need to be the same across routers BUT areas need to be identical. 

Wildcard mask is just -255 so say for a subnet of 255.255.255.192 the wildcard would be 255 - 192 = 63.

Configuring ospf on interface just requires going into interface and using ip ospf *process id* area *number* 

Rules to make Neighbor Adjacency - 
    Same Subnet
    Same OSPF area
    Same Timer (Hello Interval)
    Same Authentication 

For OSPF to converge this has to be identical to become neighbors.

Point to point - 
When using OSPF the router understands that the link is point to point, because of this it doesn't decide on a DR router or BDR router, instead of DR or BDR the link will show as P2P in the ospf neighbors along with this the state will show as FULL/*empty*. 

Router ID - 
    1. RID is manually configured
    2. Loopback with highest IP
    3. Highest IP on any active interface
This order is as numbered, router will check for manually configured RID if not configured will then check loopback and if not configured will use highest IP on any active interface.

Broadcast (DR/BDR selection) - 
DR Router election process - 
    Priority (Default is 1)
    Router ID (Highest router ID)

Any routers that are part of the ospf network that aren't the DR/BDR routers are referred to as DROTHER.




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