Sunday, 11 November 2018

Routing Protocol Authentication (RIP, and OSPF)

Routing Protocol Authentication (OSPF, and RIPv2)
A router authenticates the source of each routing update packet that it receives. Many routings' protocols support authentication like OSPF, EIGRP, ISIS, BGP, and RIPv2.
Cisco routers support different approaches to authentication route advertisements received from a neighboring router:
Plain text authentication
Hashing authentication (using MD5)

Simple password authentication:
The router sends packets and keys (if a routing protocol doesn’t support multiple keys, the key number associated with a routing update is 0). The neighboring router checks whether the key matches its key. The outing update is rejected if the keys do not match. The only routing protocols that plan text authentication are RIPv2, OSPF, and ISIS.
MD5 authentication
Configure a key (password) and key ID, router generates a message digest or hash of the key, key ID, and message. The message digest is sent with the packet key is not sent. The neighboring router receives the update and runs a hashing algorithm on the routing update with the local key, the results in a hash digest. If the hash digit matches, the router accepts the packet, if it does not the update is rejected. This process is more secure than plain text authentication. IS-IS, OSPF, RIPv2 and EIGRP use MD5.
Let’s see the configuration:

Topology:

Goal:

configure the topology and interface as per the diagram
configure RIPv2 on both the routers and advertise the interface as per the topology
make sure both the routers exchange the routes only after successful authentication.

R1#show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 10.1.1.1 YES manual up up

Serial3/0 1.1.1.1 YES manual up up

R2#show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 20.1.1.1 YES manual up up

Serial3/0 1.1.1.2 YES manual up up

R1(config)#router rip

R1(config-router)#version 2

R1(config-router)#network 1.0.0.0

R1(config-router)#network 10.0.0.0

R1(config-router)#no auto-summary

R1(config-router)#end

R2(config)#router rip

R2(config-router)#version 2

R2(config-router)#network 1.0.0.0

R2(config-router)#network 20.0.0.0

R2(config-router)#no auto-summary

R2(config-router)#end

R1#show ip route rip

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

R 20.0.0.0/8 [120/1] via 1.1.1.2, 00:00:07, Serial3/0

R2#show ip route rip

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

R 10.0.0.0/8 [120/1] via 1.1.1.1, 00:00:21, Serial3/0

configuring authentication:

R1(config)#key chain anyname1

R1(config-keychain)#key 1

R1(config-keychain-key)#key-string internetworks

R1(config)#interface serial 3/0

R1(config-if)#ip rip authentication md

R1(config-if)#ip rip authentication key-chain anyname1

R2(config)#key chain anyname2

R2(config-keychain)#key 1

R2(config-keychain-key)#key-string internetworks

R2(config-keychain-key)#end

R2(config)#interface serial 3/0

R2(config-if)#ip rip authentication mode md5

R2(config-if)#ip rip authentication key-chain anyname2

R1#show ip route

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 1.0.0.0/8 is directly connected, Serial3/0

L 1.1.1.1/32 is directly connected, Serial3/0

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.0.0.0/8 is directly connected, FastEthernet0/0

L 10.1.1.1/32 is directly connected, FastEthernet0/0

R 20.0.0.0/8 [120/1] via 1.1.1.2, 00:00:26, Serial3/0

R2#clear ip route *

R2#sh ip route

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 1.0.0.0/8 is directly connected, Serial3/0

L 1.1.1.2/32 is directly connected, Serial3/0

R 10.0.0.0/8 [120/1] via 1.1.1.1, 00:00:09, Serial3/0

20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 20.0.0.0/8 is directly connected, FastEthernet0/0

L 20.1.1.1/32 is directly connected, FastEthernet0/0

R1#show key chain

Key-chain anyname1:

key 1 -- text "internetworks"

accept lifetime (always valid) - (always valid) [valid now]

send lifetime (always valid) - (always valid) [valid now]

R2#show key chain

Key-chain anyname2:

key 1 -- text "internetworks"

accept lifetime (always valid) - (always valid) [valid now]

send lifetime (always valid) - (always valid) [valid now]

OSPF Authentication

there are two types of authentication in OSPf

1.Simple
2.Cryptographic (MD5/ SHA)

All OSPF packet will be authenticated when you enable any formation of authentication in OSPF.

Before we start BGP configuration check out some important of BGP CCIE exam topics.

Here are the lists of all OSPF labs and theories CCNA to CCIE.

1.Open Shortest Path First (OSPF)

2.OSPF Neighbor states

3.OSPF Link State Advertisement (LSA)

4.OSPF STUB, Totally stubby, NSSA, Totally NSSA and(configuration)

5.OSPF Virtual Link

6.Route Redistribution configuration

7.Routing Protocol Authentdication (RIP, and OSPF)

8.Configuring GRE Tunnel instead of virtual link

9. OSPF Autonomous system network map configuration

let see the configuration:-

Topology:-

GOAL:

Configure the topology as per our diagram
configure OSPF in area 0 and advertise all the interfaces
configure router 1 and router 2 to exchange routes after establishing successful authentication by using clear text

R1#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 10.1.1.1 YES manual up up
Serial3/0 1.1.1.1 YES manual up down
Loopback0 11.0.0.1 YES manual up up
Loopback1 11.0.1.1 YES manual up up
Loopback2 11.0.2.1 YES manual up up
Loopback3 11.0.3.1 YES manual up up

R2#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 20.1.1.1 YES manual up up
Serial3/0 1.1.1.2 YES manual up up
Loopback0 12.0.0.1 YES manual up up
Loopback1 12.0.1.1 YES manual up up
Loopback2 12.0.2.1 YES manual up up
Loopback3 12.0.3.1 YES manual up up

R1(config)#router ospf 10
R1(config-router)#router-id 11.11.11.11
R1(config-router)#network 1.0.0.0 0.255.255.255 area 0
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
R1(config-router)#network 11.0.0.0 0.0.0.255 area 0

R2(config)#router ospf 10
R2(config-router)#router-id 12.12.12.12
R2(config-router)#network 12.0.0.0 0.0.0.255 area 0
R2(config-router)#network 20.0.0.0 0.255.255.255 area 0

R2(config-router)#network 1.0.0.0 0.255.255.255 area 0

R1(config)#interface serial 3/0

R1(config-if)#ip ospf authentication

R1(config-if)#ip ospf authentication-key internet

*Dec 5 12:09:31.047: %OSPF-5-ADJCHG: Process 10, Nbr 12.12.12.12 on Serial3/0 from FULL to DOWN, Neighbor Down: Dead timer expired

R2(config)#interface serial 3/0

R2(config-if)#ip ospf authentication

R2(config-if)#ip ospf authentication-key internet

(ip ospf authentication command you can enable plaintext authentication on the

interface level.)

*Dec 5 12:16:37.095: %OSPF-5-ADJCHG: Process 10, Nbr 11.11.11.11 on Serial3/0 from LOADING to FULL, Loading Done

R1#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

12.12.12.12 0 FULL/ - 00:00:39 1.1.1.2 Serial3/0

R2#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

11.11.11.11 0 FULL/ - 00:00:39 1.1.1.1 Serial3/0

(When we have lots of interfaces do not want to enable OSPF authentication for

each and every interface. we can also enable area-wide authentication by using the area

authentication command).

let's see: -

R1(config)#router ospf 10

R1(config-router)#area 0 authentication

R1(config-router)#end

*Dec 5 12:27:32.931: OSPF-10 EVENT: Area config: 'area 0 authentication '

R2(config)#router ospf 10

R2(config-router)#area 0 authentication

R1#show ip ospf interface serial 3/0

Serial3/0 is up, line protocol is up

Internet Address 1.1.1.1/8, Area 0, Attached via Network Statement

Process ID 10, Router ID 11.11.11.11, Network Type POINT_TO_POINT, Cost: 64

Topology-MTID Cost Disabled Shutdown Topology Name

0 64 no no Base

Transmit Delay is 1 sec, State POINT_TO_POINT

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

oob-resync timeout 40

Hello due in 00:00:00

Supports Link-local Signaling (LLS)

Cisco NSF helper support enabled

IETF NSF helper support enabled

Index 1/1, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 1, maximum is 1

Last flood scan time is 0 msec, maximum is 0 msec

Neighbor Count is 1, Adjacent neighbor count is 1

Adjacent with neighbor 12.12.12.12

Suppress hello for 0 neighbor(s)

Simple password authentication enabled

R2#show ip ospf interface serial 3/0

Serial3/0 is up, line protocol is up

Internet Address 1.1.1.2/8, Area 0, Attached via Network Statement

Process ID 10, Router ID 12.12.12.12, Network Type POINT_TO_POINT, Cost: 64

Topology-MTID Cost Disabled Shutdown Topology Name

0 64 no no Base

Transmit Delay is 1 sec, State POINT_TO_POINT

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

oob-resync timeout 40

Hello due in 00:00:04

Supports Link-local Signaling (LLS)

Cisco NSF helper support enabled

IETF NSF helper support enabled

Index 2/2, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 1, maximum is 1

Last flood scan time is 0 msec, maximum is 0 msec

Neighbor Count is 1, Adjacent neighbor count is 1

Adjacent with neighbor 11.11.11.11

Suppress hello for 0 neighbor(s)

Simple password authentication enabled

What is OSPF STUB, totally stubby, NSSA, Totally NSSA and (configuration)?

OSPF STUBS

OSPF stubs allow the OSPF routers in an area to use default routes for forwarding packets to Area Border Routers (ABRs), rather than more specific routes. OSPF stubs reduce memory consumption and CPU processing time on the routers inside the area because the routers in that area can have fewer LSAs in their LSDBs.

If you configure a stub area it will block all type 5 external LSAs (E1 and E2 routes). All the prefixes you redistributed into OSPF from another routing protocol are not welcome in the stub area. Default routes are advertised into stub areas by the ABR. All OSPF routers in the stub area must be configured as stubs.

In short: the OSPF stub allows the routers in an area to use the default route for forwarding packets to ABR rather than more specific routes.

OSPF has special area types called stub areas:

Stub
Totally Stubby
Not-So-Stubby Area (NSSA)
Totally Not So Stubby Area (Totally NSSA)

Stub Area Rules:

In the OSPF Stub area, there should not be an ASBR.
The OSPF Stub area should not be Area 0.
No virtual link must be passing through that area.
All routers in that area must be configured as stub routers.

A stub area is an isolated area that does not receive External LSA. Routers in Stub areas do not receive type 4 and type 5 LSAs it is replaced by a default route to an external autonomous system advertised by the area border router (ABR) Stub areas can have type 1, 2, and 3 OSPF LSAs.

Totally stubby area External LSAs are stopped (E1 and E2) and summary LSAs are stopped (OIA routes). Replaced by a default route to other areas advertised by the ABR. Totally stubs is reducing the routing table to a minimum. This is a Cisco proprietary feature.

NSSA breaks stub area rules. NSSA area creates a special type of link-state advertisement (LSA) known as type 7, type 7 LSAs is only exist in the NSSA area. An NSSA autonomous system boundary router (ASBR) generates this LSA and an NSSA area border router (ABR) translates it into a type 5 LSA, ABR sends default routes into NSSA instead of external routes from other ASBR.

Totally NSSAs are similar to totally stubby areas, with the exception that the routers that are internal to the totally NSSAs need to have no knowledge of subnets outside of the area (with the exception of the routes injected by the NSSA ASBR)

Before we start BGP configuration check out some important BGP CCIE exam topics.

Here are the lists of all OSPF labs and theories CCNA to CCIE.

1.Open Shortest Path First (OSPF)

2.OSPF Neighbor states

3.OSPF Link State Advertisement (LSA)

4.OSPF STUB, Totally stubby, NSSA, Totally NSSA and(configuration)

5.OSPF Virtual Link

6.Route Redistribution configuration

7.Routing Protocol Authentdication (RIP, and OSPF)

8.Configuring GRE Tunnel instead of virtual link

9. OSPF Autonomous system network map configuration

Stub configuration:

Topology:

GOAL:

configure the topology and advertise the interfaces as per diagram.
configure ospf as per the diagram and redistribute RIP routes in to OSPF on R4.
configure area 10 to stop LSA 5 and LSA 4.
make sure that the area 10 routers still able to reach the external routes.

R1#show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 10.1.1.1 YES manual up up

Serial3/0 1.1.1.1 YES manual up up

Loopback0 11.0.0.1 YES manual up up

Loopback1 11.0.1.1 YES manual up up

Loopback2 11.0.2.1 YES manual up up

Loopback3 11.0.3.1 YES manual up up

R2#show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 20.1.1.1 YES manual up up

Serial3/0 1.1.1.2 YES manual up up

Serial3/1 2.1.1.1 YES manual up up

Loopback0 12.0.0.1 YES manual up up

Loopback1 12.0.1.1 YES manual up up

Loopback2 12.0.2.1 YES manual up up

Loopback3 12.0.3.1 YES manual up up

R3#show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 30.1.1.1 YES manual up up

Serial3/1 2.1.1.2 YES manual up up

Serial3/2 3.1.1.1 YES manual up up

Loopback0 13.0.0.1 YES manual up up

Loopback1 13.0.1.1 YES manual up up

Loopback2 13.0.2.1 YES manual up up

Loopback3 13.0.3.1 YES manual up up

R4#show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 40.1.1.1 YES manual up up

Serial3/2 3.1.1.2 YES manual up up

Loopback0 14.0.0.1 YES manual up up

Loopback1 14.0.1.1 YES manual up up

Loopback2 14.0.2.1 YES manual up up

Loopback3 14.0.3.1 YES manual up up

R1(config)#router ospf 1

R1(config-router)# network 11.0.0.0 0.255.255.255 area 10

R1(config-router)#network 1.0.0.0 0.255.255.255 area 10

R1(config-router)#network 10.0.0.0 0.255.255.255 area 10

R2(config)#router ospf 1

R2(config-router)#network 1.0.0.0 0.255.255.255 area 10

R2(config-router)#network 2.0.0.0 0.255.255.255 area 0

R2(config-router)#network 20.0.0.0 0.255.255.255 area 0

R2(config-router)#network 12.0.0.0 0.255.255.255 area 0

R2(config-router)#end

R3(config)#router ospf 1

R3(config-router)#network 30.0.0.0 0.255.255.255 area 0

R3(config-router)#network 13.0.0.0 0.255.255.255 area 0

R3(config-router)#network 2.0.0.0 0.255.255.255 area 0

R3(config-router)#network 3.0.0.0 0.255.255.255 area 20

R4(config)#router rip

R4(config-router)#version 2

R4(config-router)#network 14.0.0.0

R4(config-router)#no auto-summary

R4(config-router)#end

R4(config)#router ospf 1

R4(config-router)#network 3.0.0.0 0.255.255.255 area 20

R4(config-router)#network 40.0.0.0 0.255.255.255 area 20

R4(config-router)#redistribute rip subnets

R4(config-router)#end

R1#show ip route ospf

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

O IA 2.0.0.0/8 [110/128] via 1.1.1.2, 00:06:24, Serial3/0

O IA 3.0.0.0/8 [110/192] via 1.1.1.2, 00:06:24, Serial3/0

12.0.0.0/32 is subnetted, 4 subnets

O IA 12.0.0.1 [110/65] via 1.1.1.2, 00:02:08, Serial3/0

O IA 12.0.1.1 [110/65] via 1.1.1.2, 00:02:08, Serial3/0

O IA 12.0.2.1 [110/65] via 1.1.1.2, 00:02:08, Serial3/0

O IA 12.0.3.1 [110/65] via 1.1.1.2, 00:02:08, Serial3/0

13.0.0.0/32 is subnetted, 4 subnets

O IA 13.0.0.1 [110/129] via 1.1.1.2, 00:00:28, Serial3/0

O IA 13.0.1.1 [110/129] via 1.1.1.2, 00:00:28, Serial3/0

O IA 13.0.2.1 [110/129] via 1.1.1.2, 00:00:28, Serial3/0

O IA 13.0.3.1 [110/129] via 1.1.1.2, 00:00:28, Serial3/0

14.0.0.0/24 is subnetted, 4 subnets

O E2 14.0.0.0 [110/20] via 1.1.1.2, 00:04:59, Serial3/0

O E2 14.0.1.0 [110/20] via 1.1.1.2, 00:04:59, Serial3/0

O E2 14.0.2.0 [110/20] via 1.1.1.2, 00:04:59, Serial3/0

O E2 14.0.3.0 [110/20] via 1.1.1.2, 00:04:59, Serial3/0

O IA 20.0.0.0/8 [110/65] via 1.1.1.2, 00:06:24, Serial3/0

O IA 30.0.0.0/8 [110/129] via 1.1.1.2, 00:06:24, Serial3/0

R2#show ip route ospf

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

O IA 3.0.0.0/8 [110/128] via 2.1.1.2, 00:07:04, Serial3/1

O 10.0.0.0/8 [110/65] via 1.1.1.1, 00:06:54, Serial3/0

11.0.0.0/32 is subnetted, 4 subnets

O 11.0.0.1 [110/65] via 1.1.1.1, 00:03:54, Serial3/0

O 11.0.1.1 [110/65] via 1.1.1.1, 00:03:54, Serial3/0

O 11.0.2.1 [110/65] via 1.1.1.1, 00:03:54, Serial3/0

O 11.0.3.1 [110/65] via 1.1.1.1, 00:03:54, Serial3/0

13.0.0.0/32 is subnetted, 4 subnets

O 13.0.0.1 [110/65] via 2.1.1.2, 00:01:04, Serial3/1

O 13.0.1.1 [110/65] via 2.1.1.2, 00:01:04, Serial3/1

O 13.0.2.1 [110/65] via 2.1.1.2, 00:01:04, Serial3/1

O 13.0.3.1 [110/65] via 2.1.1.2, 00:01:04, Serial3/1

14.0.0.0/24 is subnetted, 4 subnets

O E2 14.0.0.0 [110/20] via 2.1.1.2, 00:05:34, Serial3/1

O E2 14.0.1.0 [110/20] via 2.1.1.2, 00:05:34, Serial3/1

O E2 14.0.2.0 [110/20] via 2.1.1.2, 00:05:34, Serial3/1

O E2 14.0.3.0 [110/20] via 2.1.1.2, 00:05:34, Serial3/1

O 30.0.0.0/8 [110/65] via 2.1.1.2, 00:07:04, Serial3/1

R2#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

13.0.3.1 0 FULL/ - 00:00:39 2.1.1.2 Serial3/1

11.0.3.1 0 FULL/ - 00:00:37 1.1.1.1 Serial3/0

R1#traceroute 14.0.0.1

Type escape sequence to abort.

Tracing the route to 14.0.0.1

VRF info: (vrf in name/id, vrf out name/id)

1 1.1.1.2 36 msec 36 msec 32 msec

2 2.1.1.2 124 msec 128 msec 144 msec

3 3.1.1.2 132 msec 92 msec 108 msec

we configure area 10 as stub, ensure that no external routes enter in to area 10.

R1(config)#router ospf 1

R1(config-router)#area 10 stub

R2(config)#router ospf 1

R2(config-router)#area 10 stub

R2#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

13.0.3.1 0 FULL/ - 00:00:31 2.1.1.2 Serial3/1

11.0.3.1 0 FULL/ - 00:00:34 1.1.1.1 Serial3/0

R1#show ip route ospf

Codes: L - local, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is 1.1.1.2 to network 0.0.0.0

O*IA 0.0.0.0/0 [110/65] via 1.1.1.2, 00:02:22, Serial3/0

O IA 2.0.0.0/8 [110/128] via 1.1.1.2, 00:02:22, Serial3/0

O IA 3.0.0.0/8 [110/192] via 1.1.1.2, 00:02:22, Serial3/0

12.0.0.0/32 is subnetted, 4 subnets

O IA 12.0.0.1 [110/65] via 1.1.1.2, 00:02:22, Serial3/0

O IA 12.0.1.1 [110/65] via 1.1.1.2, 00:02:22, Serial3/0

O IA 12.0.2.1 [110/65] via 1.1.1.2, 00:02:22, Serial3/0

O IA 12.0.3.1 [110/65] via 1.1.1.2, 00:02:22, Serial3/0

13.0.0.0/32 is subnetted, 4 subnets

O IA 13.0.0.1 [110/129] via 1.1.1.2, 00:02:22, Serial3/0

O IA 13.0.1.1 [110/129] via 1.1.1.2, 00:02:22, Serial3/0

O IA 13.0.2.1 [110/129] via 1.1.1.2, 00:02:22, Serial3/0

O IA 13.0.3.1 [110/129] via 1.1.1.2, 00:02:22, Serial3/0

O IA 20.0.0.0/8 [110/65] via 1.1.1.2, 00:02:22, Serial3/0

O IA 30.0.0.0/8 [110/129] via 1.1.1.2, 00:02:22, Serial3/0

R1#ping 14.0.0.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 14.0.0.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 80/90/100 ms

(comment me if you want the configuration of nssa, totally nssa. free of cost)

CLICK HERE TO GET NSSA and TOTALLY NSSA

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Friday, 9 November 2018

OSPF Link State Advertisement (LSA)

OSPF uses an LSDB (link state database) and fills this with LSAs (link state advertisement) LSA holds the topology information and LSA is held in the LSDB. Instead of using 1 LSA packet, OSPF has many different varieties of LSAs.

Here is the list:

LSA Types	Description
Type 1	Router LSAs
Type 2	Network LSAs
Type 3 or 4	Summary LSAs
Type 5	Autonomous system external LSAs
Type 6	Multicast OSPF LSAs
Type 7	Defined for not-so-stubby areas
Type 8	External attribute LSAs for Border Gateway Protocol (BGP)
Type 9, 10, and 11	Opaque LSAs

LSA Type 1: Router LSA

Type 1 router LSA is generated by internal routers. You can identify the “O” routes in the routing table, Type 1 LSA floods within its area only; does not cross ABR. In the type 1 LSA, you will find a list with all the directly connected links of this router.

LSA Type 2: Network LSA

The network LSA or Type 2 creates for each multi-access network. LSA Type 2 is advertised by the DR of the transit network and floods within its area only, network LSA does not cross ABR. You can identify “0” routes in the routing table. In Type 2 LSA you will find all the routers that are connected to the multi-access network, the DR, and the prefix and subnet mask.

LSA Type 3: Summary LSA

The summary LSA is created by the ABR to send updates from one area to another area. You can identify is “OIA” routes in the routing table. Summary LSA is used to flood network information subnet in the Origin area and cost but does not topology data.

LSA Type 4: ASBR summary LSA

Type 4 LSA is used to advertise ASBR to all other areas in the autonomous system. ASBR summary LSA includes the router ID of the ASBR in the link-state ID field.

LSA Type 5: External LSA

Type 5 LSA External LSA also known as autonomous system external LSA, AS external LSA created by ASBR for external routes redistributed into OSPF (LSA 5), external LSAs are advertised and owned by the originating ASBR. External LSAs flood through the entire autonomous system, and advertising router ID (ASBR) is unchanged throughout the system. Type 4 LSA is needed to find the ASBR.

LSA-6 Multicast OSPF LSA

Type 6 LSA are used in multicast routing (MOSPF routing protocol) multicast LSA (Cisco routers do not support)

LSA Type 7: NSSA external

Type 7 LSA is created by ASBR inside an NSSA, instead of a type 5 LSA. Type 7 LSA flooded only within its area of origin and converted to Type 5 LSA on an ABR toward another area.

· N1- metric increases as it is passed through the network

· N2- metric doesn’t increase (default)