Archives for the month of: April, 2011

Most things in networking are not revolutionary. No need to reinvent the wheel.

After many years of continuous growth of your backbone network, you might decide to clean up the mess and renumber the network within one single IP prefix covering the whole area. If OSPF is your choice for the interior routing protocol for IPv4, this is the right time to think again about using the OSPF network statements. A single network statement per router is all you need to make all the backbone interfaces seen by the OSPF process.
Here, for example, all the backbone is covered by a single prefix 10.0.0.0/8:
interface FastEthernet0/0
 ip address 10.1.0.0 255.255.255.254
!
router ospf 4
 passive-interface default
 no passive-interface FastEthernet0/0
 ! all backbone links are derived from 10.0.0.0/8
 network 10.0.0.0 0.255.255.255 area 0
!

What happens if we add another interface within the same global 10.0.0.0/8 to the OSPF, but we are putting it into a different OSPF area. For this exception we have to use a more specific network statement, for example:
interface Vlan991
 ip address 10.4.4.4 255.255.255.254
!
router ospf 4
 ! adding Vlan991 to area 4 with a /32 network statement
 no passive-interface Vlan991
 network 10.4.4.4 0.0.0.0 area 4
!

Will it work or will it cause conflict with the “network 10.0.0.0 0.255.255.255 area 0” statement?
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IPv6 comes with 128-bit addressing. The huge number of all theoretically possible IPv6 addresses is something human beings can not imagine.

The unthinkable number 2128, which is the number of all possible combinations of 128 bits that form an IPv6 address, is so huge that we can not scope with. For example, a precise answer to a question “How many IP addresses are available in IPv6 compared to IPv4” is:

There are 79228162514264337593543950336 times more IP addresses in v6 compared to v4.

You, as myself, might find that information pretty much useless. Let us find some down-to-earth comparisons.
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