AI, ML, Development + Cisco Learning Blog Learning about Machine Learning, Artificial Intelligence, related devlopment topics and formerly Routing and Switching, Datacenter, Security and other topics, CCIE #23664, Frank Wagner

23. Mai 2006


Filed under: OSPF — ocsic @ 17:51

Also important to know are the LSA Types OSPF speaks to other routers

The type indicates and tells something about the area type. The following exist:

  • Type 1  is an info about routers and directly connected links
  • Type 2 info about LAN and routers connected
  • Type 3 Networks reachable outside the area
  • Type 4 reachability info to the autonomous system board from the ABR
  • Type 5 info about destinations outside the OSPF domain from an ASBR
  • Type 6 multicast info
  • Type 7 NSSA area

OSPF Areas

Filed under: OSPF — ocsic @ 17:47

When you start with OSPF, everything seems to be simple. But later on you learn about many differnent types of OSPF areas.

  • Stub area – has no connection to external networks, it does not contain any external routes, relieys mostly on default routes, does not have AS-external routes (Type 5 LSAs)
  • Totaly Stub area – is an extension to the stub area and includes external routes and routes to other area over a default route, get these by Typ 3LSAs, does not support summary routes
  • Backbone area – is always area zero
  • NSSA, Not so stubby area – the same as SA, but can import external routes and send them to the backbone or other areas, type 3 and type 4 summary routes are not advertised into NSSA


ospf – summarize areas

Filed under: OSPF — ocsic @ 10:26

If you want to summarize areas in the routing table of router behind an ABR you could use the following command in OSPF Router configuration mode.
area 1 range

With this command, als subnets belonging to are not showing up in the routing table of routers behind the ABR.

Stub area

Filed under: OSPF — ocsic @ 08:23

If you don’t want to show up all your routes in a routing table of a stub router, use the „no-summary“ command at the router next to the stub router.

If you have one router configured with the „area 1 stub“ command use the „area 1 stub no-summary“ command on the other router to just let a default router show up in the stub router.

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