Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

redistributing RIP subnets into OSPF NSSA Area

What is the correct Answer

NSSA Area OPSF.jpg

PS4A will redistribute RIP Subnets as Type 7 into NSSA , and then PS4B will flood Type 7 LSAs throughout the backbone

or

PS4A will redistribute RIP Subnets as Type 7 into NSSA , and then PS4B  will translate Type 7 LSAs into Type 5 before flooding throughout the backbone

2 ACCEPTED SOLUTIONS

Accepted Solutions

Re: redistributing RIP subnets into OSPF NSSA Area

This one is the correct answer :

PS4A will redistribute RIP Subnets as Type 7 into NSSA , and then PS4B  will translate Type 7 LSAs into Type 5 before flooding throughout the backbone

When you perform redistribution in NSSA, it shows up as N1 or N2 routes in NSSA area but when the ABR connecting NSSA to Backbone advertises it further it will change the Type 7 external to Type 5 external and shows up as E1 or E2.

HTH

Hitesh Vinzoda

Please rate useful posts.

Hall of Fame Super Silver

Re: redistributing RIP subnets into OSPF NSSA Area

Hello Sohail,

an OSPF NSSA area is an area that cannot receive LSA type 5 from backbone as any other stub area type.

However, special LSA type 7 can be used by an ASBR node internal to the stub area to inject external routes into the OSPF domain.

LSA type 7 cannot go out of the OSPF NSSA area in which they are generated. Depending on a setting on ASBR node PSA, the ABR node between OSPF NSSA area and backbone area will translate the OSPF LSA type 7 in a an OSPF LSA type 5 that can be propagated to the backbone and to all non stub areas (standard areas)

So OSPF NSSA is a design tool that allows the following:

to minimize OSPF database size

to allow to import routes in the area without the need to import all the external routes in OSPF domain

to even allow to import some routes that will be confined to OSPF NSSA area for local use (if P bit is not set by ASBR)

shortly the correct answer is the second one:

PS4A will redistribute RIP Subnets as Type 7 into NSSA , and then PS4B  will translate Type 7 LSAs into Type 5 before flooding throughout the backbone

Hope to help

Giuseppe

2 REPLIES

Re: redistributing RIP subnets into OSPF NSSA Area

This one is the correct answer :

PS4A will redistribute RIP Subnets as Type 7 into NSSA , and then PS4B  will translate Type 7 LSAs into Type 5 before flooding throughout the backbone

When you perform redistribution in NSSA, it shows up as N1 or N2 routes in NSSA area but when the ABR connecting NSSA to Backbone advertises it further it will change the Type 7 external to Type 5 external and shows up as E1 or E2.

HTH

Hitesh Vinzoda

Please rate useful posts.

Hall of Fame Super Silver

Re: redistributing RIP subnets into OSPF NSSA Area

Hello Sohail,

an OSPF NSSA area is an area that cannot receive LSA type 5 from backbone as any other stub area type.

However, special LSA type 7 can be used by an ASBR node internal to the stub area to inject external routes into the OSPF domain.

LSA type 7 cannot go out of the OSPF NSSA area in which they are generated. Depending on a setting on ASBR node PSA, the ABR node between OSPF NSSA area and backbone area will translate the OSPF LSA type 7 in a an OSPF LSA type 5 that can be propagated to the backbone and to all non stub areas (standard areas)

So OSPF NSSA is a design tool that allows the following:

to minimize OSPF database size

to allow to import routes in the area without the need to import all the external routes in OSPF domain

to even allow to import some routes that will be confined to OSPF NSSA area for local use (if P bit is not set by ASBR)

shortly the correct answer is the second one:

PS4A will redistribute RIP Subnets as Type 7 into NSSA , and then PS4B  will translate Type 7 LSAs into Type 5 before flooding throughout the backbone

Hope to help

Giuseppe

1277
Views
4
Helpful
2
Replies
CreatePlease to create content