Please Whitelist This Site?
I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)
If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.
If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.
Thanks for your understanding!
Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide
NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.
OSPF Basic Topology and the Link State Database (LSDB)
(Page 3 of 3)
LSDB Information Storage and Propagation
An important point to remember about
the LSDB is that even though each router maintains it, the database
isn't constructed from the perspective of the individual router. A router's
LSDB represents the topology of the entire AS, including links between
routers that may be rather distant from it. So, for example, RA
would keep the entire database in its storage area, including information
about RC and RD, to which it does not connect directly.
Since in basic topology all the routers
are peers and maintain information for the entire AS, they in theory
should have the exact same LSDB contents. When a router is first turned
on it may in fact have different LSDB information than its neighbors,
but this will be corrected through the exchange of update messages containing
link-state advertisements (LSAs). Eventually all routers should converge
to the same information. We will see how this works in the
topic on OSPF messaging.
OSPF, as an interior routing protocol,
is of course used only within the autonomous system. In most cases the
AS will be connected to other ASes through one or more of its routers.
The routers that connect the AS to other ASes are often called boundary
routers. These devices will use OSPF to communicate within the AS,
and an exterior routing protocol (typically BGP)
to talk to routers outside the AS. The name boundary router refers
to the fact that these devices are usually located on the periphery
of the AS.
Key Concept: In basic OSPF topology, each of the routers running OSPF is considered a peer of the others. Each maintains a link-state database (LSDB) that contains information about the topology of the entire autonomous system. Each link between a router and network or between two routers is represented by an entry in the LSDB that indicates the cost to send data over the link. The LSDB is updated regularly through the exchange of OSPF link-state advertisements (LSAs).
|If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Table Of Contents - Contact Us
The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.