ospf area range v. summary address...

from http://www.cisco.com/en/US/docs/ios/12_1/iproute/command/reference/1rdospf.html#wp1017596

area range

To consolidate and summarize routes at an area boundary, use the area range command in router configuration mode.

The area range command is used only with area border routers (ABRs). It is used to consolidate or summarize routes for an area. The result is that a single summary route is advertised to other areas by the ABR. Routing information is condensed at area boundaries. External to the area, a single route is advertised for each address range. This behavior is called route summarization. 

summary-address (OSPF)

Routes learned from other routing protocols can be summarized. The metric used to advertise the summary is the smallest metric of all the more specific routes. This command helps reduce the size of the routing table.

Using this command for OSPF causes an OSPF autonomous system boundary router (ASBR) to advertise one external route as an aggregate for all redistributed routes that are covered by the address. For OSPF, this command summarizes only routes from other routing protocols that are being redistributed into OSPF. Use the area range command for route summarization between OSPF areas.

and now a word from asbr...

this kinda shit drives me nuts... make up my mind...

according to cisco.com;

http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml


An area is interface specific. A router that has all of its interfaces within the same area is called an internal router (IR). A router that has interfaces in multiple areas is called an area border router (ABR). Routers that act as gateways (redistribution)between OSPF and other routing protocols (IGRP, EIGRP, IS-IS, RIP, BGP, Static) or other instances of the OSPF routing process are called autonomous system boundary router (ASBR). Any router can be an ABR or an ASBR.

according to wendell, route ocg:

ASBR Autonomous System Border Router. A router using OSPF in which the router learns routes via another source, typically another routing protocol, exchanging routes that are external to OSPF with the OSPF domain
 
according to doyle, routing tcpip vol 1

Autonomous System Boundary Routers (ASBRs) are gateways for external traffic,  injecting routes into the OSPF domain that were learned (redistributed) from some other protocol, 

according to wiki: 
http://en.wikipedia.org/wiki/Open_Shortest_Path_First

Autonomous system boundary router

An autonomous system boundary router (ASBR) is a router that is connected to more than one Routing protocol and that exchanges routing information with routers in other protocols. ASBRs typically also run an exterior routing protocol (e.g., BGP), or use static routes, or both. An ASBR is used to distribute routes received from other, external ASs throughout its own autonomous system. (An interactive ASBR simulation shows how an ASBR creates External LSA for external addresses and floods them to all areas via ABR.) Routers in other areas use ABR as next hop to access external addresses. Then ABR forwards packets to the ASBR that announces the external addresses.

then there's chris bryant...

Cisco CCNP ROUTE Exam Tutorial OSPF ASBR Route Redistribution

www.thebryantadvantage.com/Tutorial%20ASBR.htm

Cisco CCNP ROUTE certification tutorial on the OSPF Autonomous System Border Rotuer (ASBR). Route distribution between OSPF and RIP shown on a Cisco ...

choose your poison...

or let she hulk figure it out...