Not So Stubby Area

In OSPF (Open Shortest Path First) for IPv6, a Not-So-Stubby Area (NSSA) is a specialized OSPF area designed to allow the injection of external routes into the OSPF domain without the full complexity of a standard OSPF Autonomous System. In an NSSA, routers receive a default route and external routes, encapsulated in Type 7 LSAs (Link State Advertisements). These Type 7 LSAs are then converted into Type 5 LSAs as they traverse the OSPF domain. The NSSA is particularly useful in scenarios where an OSPF network connects to external networks, such as the internet, and there is a need to maintain a degree of summarization within the OSPF domain. NSSAs offer a compromise between the simplicity of a Stub Area and the requirement to convey external routing information into OSPF networks. This approach helps optimize routing efficiency while still allowing routers within the NSSA to reach external destinations through the summarization provided by the default route.

Lab:

Disclaimer

This Configuration Guide is designed to assist members to enhance their skills in particular technology area. While every effort has been made to ensure that all material is as complete and accurate as possible, the enclosed material is presented on an Dzas isdz basis. Neither the authors nor Forum assume any liability or responsibility to any person or entity with respect to loss or damages incurred from the information contained in this guide. This configuration guide was developed by Forum. Any similarities between material presented in this configuration guide and any other material is completely coincidental.

Cisco IOS Software, Linux Software (I86BI_LINUX-ADVENTERPRISEK9-M), Version 15.2(4)M1, DEVELOPMENT TEST SOFTWARE

Task 1: Configure IPv6 OSPF Not So Stubby Area (NSSA)

Step 1: In the configuration mode of router configure loopbacks & redistribute these connected network in IPv6 OSPF process:

R1:
interface loopback 50
ipv6 address 50::1/64
exit

R1:
ipv6 router ospf 1
redistribute connected 
exit
R2#show ipv6 route
! (Shows router’s routing table and IPv6 routes entries)

IPv6 Routing Table - default - 22 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
       H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
       IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
       ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP
O   11:0:1::1/128 [110/64]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
O   11:0:2::1/128 [110/64]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
O   11:0:3::1/128 [110/64]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
C   12::/64 [0/0]
     via Serial2/0, directly connected
L   12::A8BB:CCFF:FE00:200/128 [0/0]
     via Serial2/0, receive
C   22:0:1::/64 [0/0]
     via Loopback1, directly connected
L   22:0:1::2/128 [0/0]
     via Loopback1, receive
C   22:0:2::/64 [0/0]
     via Loopback2, directly connected
L   22:0:2::2/128 [0/0]
     via Loopback2, receive
C   22:0:3::/64 [0/0]
     via Loopback3, directly connected
L   22:0:3::2/128 [0/0]
     via Loopback3, receive
C   23::/64 [0/0]
     via Ethernet0/0, directly connected
L   23::A8BB:CCFF:FE00:200/128 [0/0]
     via Ethernet0/0, receive
O   33:0:1::3/128 [110/10]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O   33:0:2::3/128 [110/10]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O   33:0:3::3/128 [110/10]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  34::/64 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  44:0:1::4/128 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  44:0:2::4/128 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  44:0:3::4/128 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OE2 50::/64 [110/20]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
L   FF00::/8 [0/0]
     via Null0, receive

Step 2: Configure IPv6 OSPF Not So Stubby Area

! (When loop50 is redistributed in stub area, external routes LSA 5 will no propagate in stub area and hence cannot be seen in any other router’s routing table. To make seen this redistributed route to all other routers, replace stub area to Not So Stubby Area.)

R1:
ipv6 router ospf 1
area 1 nssa
exit

R2:
ipv6 router ospf 1
area 1 nssa
exit

Task 2: Verification:

Step 1: Verify routes on neighbor router routing table

R2#show ipv6 route
! (Shows router’s routing table and IPv6 routes entries)

IPv6 Routing Table - default - 22 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
       H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
       IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
       ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP
O   11:0:1::1/128 [110/64]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
O   11:0:2::1/128 [110/64]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
O   11:0:3::1/128 [110/64]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
C   12::/64 [0/0]
     via Serial2/0, directly connected
L   12::A8BB:CCFF:FE00:200/128 [0/0]
     via Serial2/0, receive
C   22:0:1::/64 [0/0]
     via Loopback1, directly connected
L   22:0:1::2/128 [0/0]
     via Loopback1, receive
C   22:0:2::/64 [0/0]
     via Loopback2, directly connected
L   22:0:2::2/128 [0/0]
     via Loopback2, receive
C   22:0:3::/64 [0/0]
     via Loopback3, directly connected
L   22:0:3::2/128 [0/0]
     via Loopback3, receive
C   23::/64 [0/0]
     via Ethernet0/0, directly connected
L   23::A8BB:CCFF:FE00:200/128 [0/0]
     via Ethernet0/0, receive
O   33:0:1::3/128 [110/10]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O   33:0:2::3/128 [110/10]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
O   33:0:3::3/128 [110/10]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  34::/64 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  44:0:1::4/128 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  44:0:2::4/128 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
OI  44:0:3::4/128 [110/74]
     via FE80::A8BB:CCFF:FE00:300, Ethernet0/0
ON2 50::/64 [110/20]
     via FE80::A8BB:CCFF:FE00:100, Serial2/0
L   FF00::/8 [0/0]
     via Null0, receive

(R2 receives external routes E2 through Not so Stubby Area (NSSA) and marked as N2.)

R3#show ipv6 route
! (Shows router’s routing table and IPv6 routes entries)

IPv6 Routing Table - default - 22 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
       B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
       H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
       IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
       ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
       O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP

OI  11:0:1::1/128 [110/74]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
OI  11:0:2::1/128 [110/74]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
OI  11:0:3::1/128 [110/74]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
OI  12::/64 [110/74]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
O   22:0:1::2/128 [110/10]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
O   22:0:2::2/128 [110/10]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
O   22:0:3::2/128 [110/10]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
C   23::/64 [0/0]
     via Ethernet0/0, directly connected
L   23::A8BB:CCFF:FE00:300/128 [0/0]
     via Ethernet0/0, receive
C   33:0:1::/64 [0/0]
     via Loopback1, directly connected
L   33:0:1::3/128 [0/0]
     via Loopback1, receive
C   33:0:2::/64 [0/0]
     via Loopback2, directly connected
L   33:0:2::3/128 [0/0]
     via Loopback2, receive
C   33:0:3::/64 [0/0]
     via Loopback3, directly connected
L   33:0:3::3/128 [0/0]
     via Loopback3, receive
C   34::/64 [0/0]
     via Serial2/0, directly connected
L   34::A8BB:CCFF:FE00:300/128 [0/0]
     via Serial2/0, receive
O   44:0:1::4/128 [110/64]
     via FE80::A8BB:CCFF:FE00:400, Serial2/0
O   44:0:2::4/128 [110/64]
     via FE80::A8BB:CCFF:FE00:400, Serial2/0
O   44:0:3::4/128 [110/64]
     via FE80::A8BB:CCFF:FE00:400, Serial2/0
OE2 50::/64 [110/20]
     via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
L   FF00::/8 [0/0]
     via Null0, receive

(R3 receives external routes E2 through Not so Stubby Area (NSSA) forwarded by ABR R2 and marked as E2.)

R3 receives external routes E1 through Not so Stubby Area (NSSA) forwarded by ABR R2 and marked as E1