NSSA Regional Default-information-originate/no-redistribution/no-summary Differences

The LSA of OSPF has 11 classes, commonly used is 1 (router itself), 3 (network summary), 5 class (as external route);

Class 7 LSA (7 classes of LSA is generated under a non-complete peripheral region)

NSSA (Not-so-stubby area) is an LSA originating from the ASBR router in the NSSA region that advertises that it only floods within the NSSA region, and that the 5-class LSA difference is the range of the propagation (5 classes are flooded throughout the as region and 7 classes can only flood in the NSSA region)

such as the network topology (cannot insert pictures really troublesome):

External---R1---R2---R3---R4----R5---R6

R1/r2 in Area 2

R2/r3 in Area 0

R3/R4/R5 in area 1 for Nssa Zone

R5/R6 simulates the external network.

Configuration of the Nssa zone:

Configuration information for R3:

Router OSPF 1
Log-adjacency-changes
Area 1 Nssa
Redistribute connected subnets
Network 192.168.2.0 0.0.0.255 Area 0
Network 192.168.3.0 0.0.0.255 Area 1
!

If there is an injection of external routes on the border routers of other non-NSSA regions, such as RIP routing injection;

Configure on the R1

Router OSPF 1
Log-adjacency-changes
Redistribute RIP metric 1 subnets
Network 1.1.1.0 0.0.0.255 Area 2
Network 192.168.1.0 0.0.0.255 Area 2
!
Router RIP
Version 2
Redistribute OSPF 1 metric 1
Network 10.0.0.0
No auto-summary
!

To view routing information:

R3 View of Routes

R3#show IP route
CODES:C-connected, s-static, R-rip, M-mobile, B-BGP
D-EIGRP, Ex-eigrp External, O-OSPF, IA-OSPF Inter area
N1-OSPF NSSA External Type 1, N2-OSPF NSSA external type 2
E1-OSPF external Type 1, E2-OSPF external type 2
I-is-is, Su-is-is Summary, L1-is-is level-1, L2-is-is level-2
Ia-is-is Inter area, *-candidate default, U-per-user static route
O-ODR, P-periodic downloaded static route
Gateway of last resort are not set
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/3] via 192.168.2.2, 01:43:05, FASTETHERNET0/1
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 192.168.2.2, 01:43:10, FASTETHERNET0/1
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, LOOPBACK3
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/11] via 192.168.3.4, 01:43:05, ETHERNET1/1
5.0.0.0/32 is subnetted, 1 subnets
O 5.5.5.5 [110/21] via 192.168.3.4, 01:43:05, ETHERNET1/1
O 192.168.4.0/24 [110/20] via 192.168.3.4, 01:43:05, ETHERNET1/1
O N2 192.168.5.0/24 [110/20] via 192.168.3.4, 01:42:58, ETHERNET1/1
10.0.0.0/24 is subnetted, 1 subnets
O E2 10.1.1.0 [110/1] via 192.168.2.2, 01:43:06, FASTETHERNET0/1
O IA 192.168.1.0/24 [110/2] via 192.168.2.2, 01:43:06, FASTETHERNET0/1
C 192.168.2.0/24 is directly connected, FASTETHERNET0/1
C 192.168.3.0/24 is directly connected, ETHERNET1/1

Routing Information for R4:
R4#show IP route
CODES:C-connected, s-static, R-rip, M-mobile, B-BGP
D-EIGRP, Ex-eigrp External, O-OSPF, IA-OSPF Inter area
N1-OSPF NSSA External Type 1, N2-OSPF NSSA external type 2
E1-OSPF external Type 1, E2-OSPF external type 2
I-is-is, Su-is-is Summary, L1-is-is level-1, L2-is-is level-2
Ia-is-is Inter area, *-candidate default, U-per-user static route
O-ODR, P-periodic downloaded static route
Gateway of last resort are not set
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/13] via 192.168.3.3, 01:43:40, ETHERNET1/1
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/12] via 192.168.3.3, 01:43:40, ETHERNET1/1
3.0.0.0/24 is subnetted, 1 subnets
O N2 3.3.3.0 [110/20] via 192.168.3.3, 01:43:40, ETHERNET1/1
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback4
5.0.0.0/32 is subnetted, 1 subnets
O 5.5.5.5 [110/11] via 192.168.4.5, 01:43:40, ethernet1/0
C 192.168.4.0/24 is directly connected, ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 01:43:40, ethernet1/0
O IA 192.168.1.0/24 [110/12] via 192.168.3.3, 01:43:40, ETHERNET1/1
O IA 192.168.2.0/24 [110/11] via 192.168.3.3, 01:43:41, ETHERNET1/1
C 192.168.3.0/24 is directly connected, ETHERNET1/1
After the Nssa property is configured, the corresponding inter-domain routing information is generated, and if an external route is introduced, the default routing guarantee needs to be injected into the ABR on the Nssa area, and the NSSA zone can access the external network normally. Otherwise, there will be no network access to the situation;

The command is as follows:

Area 1 Nssa default-information-originate

Routing information on the R4:
R4#show IP route
CODES:C-connected, s-static, R-rip, M-mobile, B-BGP
D-EIGRP, Ex-eigrp External, O-OSPF, IA-OSPF Inter area
N1-OSPF NSSA External Type 1, N2-OSPF NSSA external type 2
E1-OSPF external Type 1, E2-OSPF external type 2
I-is-is, Su-is-is Summary, L1-is-is level-1, L2-is-is level-2
Ia-is-is Inter area, *-candidate default, U-per-user static route
O-ODR, P-periodic downloaded static route
Gateway of last resort are 192.168.3.3 to network 0.0.0.0
1.0.0.0/32 is subnetted, 1 subnets
O IA 1.1.1.1 [110/13] via 192.168.3.3, 01:55:07, ETHERNET1/1
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/12] via 192.168.3.3, 01:55:07, ETHERNET1/1
3.0.0.0/24 is subnetted, 1 subnets
O N2 3.3.3.0 [110/20] via 192.168.3.3, 01:55:07, ETHERNET1/1
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback4
5.0.0.0/32 is subnetted, 1 subnets
O 5.5.5.5 [110/11] via 192.168.4.5, 01:55:07, ethernet1/0
C 192.168.4.0/24 is directly connected, ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 01:55:07, ethernet1/0
O IA 192.168.1.0/24 [110/12] via 192.168.3.3, 01:55:07, ETHERNET1/1
O IA 192.168.2.0/24 [110/11] via 192.168.3.3, 01:55:07, ETHERNET1/1
C 192.168.3.0/24 is directly connected, ETHERNET1/1
o*n2 0.0.0.0/0 [110/1] via 192.168.3.3, 00:00:36, ETHERNET1/1
The routing of the Nssa zone isgenerates a default route of Class 7, flooding the entire Nssa area, along with some routing and default routing between domains, simplifying routing to reduce the number of entries in the route, and thus producing a complete peripheral area to streamline the route

Command: Area1 Nssa no-summary

The complete peripheral area automatically generates a default route for a Class 3 LSA and floods the entire Nssa region:
R4#show IP route
CODES:C-connected, s-static, R-rip, M-mobile, B-BGP
D-EIGRP, Ex-eigrp External, O-OSPF, IA-OSPF Inter area
N1-OSPF NSSA External Type 1, N2-OSPF NSSA external type 2
E1-OSPF external Type 1, E2-OSPF external type 2
I-is-is, Su-is-is Summary, L1-is-is level-1, L2-is-is level-2
Ia-is-is Inter area, *-candidate default, U-per-user static route
O-ODR, P-periodic downloaded static route
Gateway of last resort are 192.168.3.3 to network 0.0.0.0
3.0.0.0/24 is subnetted, 1 subnets
O N2 3.3.3.0 [110/20] via 192.168.3.3, 00:00:17, ETHERNET1/1
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback4
5.0.0.0/32 is subnetted, 1 subnets
O 5.5.5.5 [110/11] via 192.168.4.5, 00:00:17, ethernet1/0
C 192.168.4.0/24 is directly connected, ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 00:00:17, ethernet1/0
C 192.168.3.0/24 is directly connected, ETHERNET1/1
O*ia 0.0.0.0/0 [110/11] via 192.168.3.3, 00:00:17, ETHERNET1/1

To view database information:
Summary Net Link States (area 1)

Link ID ADV Router age seq# Checksum
0.0.0.0 3.3.3.3 137 0x80000001 0x00de4b

Note: When configuring the complete peripheral area, just configure it on the Nssa ABR, and the other NSSA routers will be configured properly.

If an external route is introduced on the route of the Nssa zone and the backbone area, such as the introduction of an external route on R3,

To view the routing information on R4:

R4#show IP route
CODES:C-connected, s-static, R-rip, M-mobile, B-BGP
D-EIGRP, Ex-eigrp External, O-OSPF, IA-OSPF Inter area
N1-OSPF NSSA External Type 1, N2-OSPF NSSA external type 2
E1-OSPF external Type 1, E2-OSPF external type 2
I-is-is, Su-is-is Summary, L1-is-is level-1, L2-is-is level-2
Ia-is-is Inter area, *-candidate default, U-per-user static route
O-ODR, P-periodic downloaded static route
Gateway of last resort are 192.168.3.3 to network 0.0.0.0
3.0.0.0/24 is subnetted, 1 subnets
O N2 3.3.3.0 [110/20] via 192.168.3.3, 00:00:17, ETHERNET1/1
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback4
5.0.0.0/32 is subnetted, 1 subnets
O 5.5.5.5 [110/11] via 192.168.4.5, 00:00:17, ethernet1/0
C 192.168.4.0/24 is directly connected, ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 00:00:17, ethernet1/0
C 192.168.3.0/24 is directly connected, ETHERNET1/1
O*ia 0.0.0.0/0 [110/11] via 192.168.3.3, 00:00:17, ETHERNET1/1

If the device has a large number of incoming routing information, this will also be a large CPU consumption of the device, in order to simplify routing introduced another command: Area1 nssa no-summary no-redistribution

R4#show IP route
CODES:C-connected, s-static, R-rip, M-mobile, B-BGP
D-EIGRP, Ex-eigrp External, O-OSPF, IA-OSPF Inter area
N1-OSPF NSSA External Type 1, N2-OSPF NSSA external type 2
E1-OSPF external Type 1, E2-OSPF external type 2
I-is-is, Su-is-is Summary, L1-is-is level-1, L2-is-is level-2
Ia-is-is Inter area, *-candidate default, U-per-user static route
O-ODR, P-periodic downloaded static route
Gateway of last resort are 192.168.3.3 to network 0.0.0.0
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback4
5.0.0.0/32 is subnetted, 1 subnets
O 5.5.5.5 [110/11] via 192.168.4.5, 00:00:03, ethernet1/0
C 192.168.4.0/24 is directly connected, ethernet1/0
O N2 192.168.5.0/24 [110/20] via 192.168.4.5, 00:00:03, ethernet1/0
C 192.168.3.0/24 is directly connected, ETHERNET1/1
O*ia 0.0.0.0/0 [110/11] via 192.168.3.3, 00:00:03, ETHERNET1/1
In general, when configuring the NSSA zone, configure the no-summary on the ABR andno-redistribution used in combination. But do not confuse, only in the Nssa area of the ABR routing configuration, the other NSSA routers are only configured as Nssa zone on the line.

NSSA Regional Default-information-originate/no-redistribution/no-summary Differences