Friday, April 27, 2012
In general, most ISPs will assign a /30 on point-to-point interfaces which gives you 4 IP addresses and 2 of which are usable resulting in 50% of addresses in that subnet being wasted. For example 188.8.131.52/30 yields 184.108.40.206 and 220.127.116.11 as your usable IP addresses and 18.104.22.168 is the subnet number and 22.214.171.124 is the broadcast address. And as you can see only 2 out of the 4 IP addresses are usable. So how we can be more efficient? The use of a /31 subnet mask which gives you 2 IP addresses and 100% of them will be utilized.
The sooner we detect OSPF neighbor failure the faster the network can converge when there is a failure. In this blogtorial we will see how we can achieve fast detection of OSPF neighbor failure. Consider this simple 2 router topology and let's get started.