OSPF - detailed explanation of NSSA area and full NSSA area (including configuration command), LSA type 7 lsa-7

Catalog

One 、NSSA Area ：

（1）——NSSA characteristic ：

（2）—— To configure :

（3）—— The illustration ：

Two 、 Completely NSSA Area ：

（1）—— Completely NSSA Regional characteristics ：

（2）—— To configure ：

3、 ... and 、LSA-7：

（1）—— brief introduction ：

（2）—— characteristic ：

（３）—— see ：

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One 、NSSA Area ：

（1）——NSSA characteristic ：

• and stub The area is similar , Just can Allow redistribution of incoming external routes within this area , The external route redistributed in is not in LSA-5 The way in , It is With LSA-7 The way in ; External routes redistributed from other areas cannot enter me NSSA Regional
• NSSA The external route that area redistributes comes in with 7 class LSA Come in , Again by NSSA Regional ABR Router （RID The big one ） hold LSA Of 7 Class to 5 Class announcement OSPF Other areas , This converted router has also become ASBR Router （R5）, So this ASBR Router area ABR In producing a 4 Class LSA Inform other areas
• NSSA In the area ABR Router is lazy , Not automatically to NSSA The normal router in the area will automatically announce the default route （stub The area will automatically announce ）, Notice needs to be specified manually
• LSA-7 Only in NSSA Flooding in the area
• Refuse : LSA-4   , LSA-5
• allow : LSA-1 / 2 / 3 / 7
• NSSA All areas ABR The router also acts as ASBR Router 【 Just some don't go on LSA-7 transformation LSA-5 nothing more ）

（2）—— To configure :

• All routers in this area need to be configured

  N-ABR(config) #router ospf 100
  N-ABR(config-router)#area 1 nssa
  N-ABR(config-router) #exit

• This area ABR The router needs to add an additional notification OSPF Configuration of the default route ：

N-ABR(config) #router ospf 100
N-ABR(config-router)#area 1 nssa default-information-originate
N-ABR(config-router) #exit

（3）—— The illustration ：

Two 、 Completely NSSA Area ：

（1）—— Completely NSSA Regional characteristics ：

• from NSSA Upgrade , Only need NSSA Regional ABR Add :no-summary
• Refuse :LSA-4,LSA-5,LSA-3, That is to say, not only the external route is rejected , meanwhile OSPF The inter region route of is also rejected
• allow :LSA-1　 LAS-2 　LSA-7 And the only one LSA-7 Default route

（2）—— To configure ：

N-ABR(config)#router ospf 100
N-ABR(config-router) #area 1 nssa default-information-originate no—summary
N-ARB(config-router)＃exit

3、 ... and 、LSA-7：

（1）—— brief introduction ：

• NSSA external LSA（NSSA External LSA）: It refers to the impure terminal area （Not-So-Stubby Area, NSSA） It starts from ASBR The router LSA notice .NSSA external LSA Announcements are almost external to autonomous systems LSA The announcement is the same . It's just not like outside the autonomous system LSA Notice that in the whole OSPF Flood diffusion in the autonomous system ,NSSA external LSA The announcement just started this NSSA external LSA Flood diffusion is carried out inside the announced impure terminal area . By command show ip ospf database nssa-external To display NSSA external LSA Announcement information .

（2）—— characteristic ：

• produce :NSSA Regional ASBR Produced
• Flood boundary :NSSA Inside the area
• effect : stay NSSA The external routes sent in by the area are LSA-7 Way in , Message format and LSA-5 equally LSA-7 Get into NSSA Area , from NSSA Regional ABR Router put LSA-7 convert to LSA-5 After the announcement OSPF Backbone area and other areas

（３）—— see ：

show ip ospf database nssa-external