OSPF Question

rakem

Doing some OSPF study, came accross this question:

OSPF offers such flexibility due to its support of hierarchical routing which of the following statements is true about OSPF hierarchy? (choose two

a:Can contain one autonomous system
b:Can contain only one area
c:Can contain multiple autonomous system
d:Can contain multiple areas

so the correct answers are A and D. I orginally chose C and D.

So the way i understand it now is that OSPF can support only one Autonomous System, howvere this AS can be divided up into multiple areas which can all have different process ID's.

Is this correct? thanks.

hectorjhrdz

OSPF is an Internal Gateway Protocol, so you can't use it for routing between 2 AS (ISPs, AS is the right name). for that issue you have the External Gateway Protocols such as BGP-4.

And as you wrote, AS are divided into areas in order to have more traffic control.



cheers

keenon

rakem wrote:

Doing some OSPF study, came accross this question:

OSPF offers such flexibility due to its support of hierarchical routing which of the following statements is true about OSPF hierarchy? (choose two

a:Can contain one autonomous system
b:Can contain only one area
c:Can contain multiple autonomous system
d:Can contain multiple areas

so the correct answers are A and D. I orginally chose C and D.

So the way i understand it now is that OSPF can support only one Autonomous System, howvere this AS can be divided up into multiple areas which can all have different process ID's.

Is this correct? thanks.

the process ids in ospf are locally significant.. unlike igrp and eigrp where it defines the local AS in which these routers participate

marlon23

You can use OSPF as a routing protocol in AS (group of devices under common control) and this AS divide into multiple areas = which is pretty good, becouse you keep topology database of routers smaller & simpler so convergence is faster, and instabillity is limited into the area. (And some advanced things exists like stubby area, totally stuby area, not-so-stubby area..)
And as was wrote, ospf uses process-id, which is sometimes usefull when you want run more ospf instances on router (but I don't know when