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)


LSA Type 8: external attribute LSA
External attribute LSA is created by ASBR during BGP to OSPF redistribution to preserve BGP attributes of the redistribution network.

LSA Type 9, 10, 11
·         Used in OSPF and BGP inter-networking




Here are the lists of all OSPF labs and theories from 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




 


 


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Thursday, 8 November 2018

OSPF Virtual Link


An Open Shortest Path First (OSPF) autonomous system all areas must be physically connected to the backbone area (Area 0). In some cases, if this is not possible, we can use a virtual link to connect to the backbone (Area 0) through a non-backbone area. We can also use the virtual links to connect two parts of a partitioned backbone (Area 0) through a non-backbone area. The area through which we configure the virtual link, known as a transit area, must have full routing information. Remember the transit area cannot be a stub area.







Virtual link must be configuring both sides with the same area ID and the corresponding virtual link OSPF neighbor router ID. Show IP OSPF neighbors command give you the router ID information.

area-id
Is identifier for the OSPF area assigned to the transit area for the virtual link. OSPF area ID can be from 0 to 4294967295 or an IP address.
router-id
Router ID is associated with the virtual link neighbor. Specify as an IP address. The router ID appears in the show IP OSPF neighbors command.



In short: virtual link are used to connect a discontiguous area to area 0, virtual link is a logical connection built between routers, virtual links are recommended for backup or temporary connections
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





configuration virtual link:

Topology:


GOAL:

  • Configure interfaces and assigned IP addresses as per the Topology
  • advertise the interfaces using multiple areas defined as per the Topology
  • configure the manual router id (RID) R1-11.1.1.1, R2-22.1.1.1, and R3-33.1.1.1
  • make sure that the loop-back of R1- 11.0.0.0 routes should be seen on all the other routers

R1#show ip interface brief

Interface              IP-Address      OK? Method Status                Protocol
FastEthernet 0/0        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                     2.2.2.1         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                    2.2.2.2         YES manual up                    up
Serial3/2                    3.3.3.1         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                   3.3.3.2         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)#router-id 11.1.1.1
R1(config-router)#NETwork 1.0.0.0 0.255.255.255 Area 20
R1(config-router)#NETwork 10.0.0.0 0.255.255.255 Area 20
R1(config-router)#NETwork 11.0.0.0 0.0.0.255 area 10

R2(config)#router ospf 1
R2(config-router)#router-id 22.1.1.1
R2(config-router)#network 1.0.0.0 0.255.255.255 area 20
R2(config-router)#network 2.0.0.0 0.255.255.255 area 20
R2(config-router)#network 20.0.0.0 0.255.255.255 area 20

R3(config)#router ospf 1
R3(config-router)#router-id 33.1.1.1
R3(config-router)#network 2.0.0.0 0.255.255.255 a 20
R3(config-router)#network 3.0.0.0 0.255.255.255 area 0
R3(config-router)#network 30.0.0.0 0.255.255.255 area 20

R4(config)#router ospf 1
R4(config-router)#network 3.0.0.0 0.255.255.255 area 0
R4(config-router)#network 40.0.0.0 0.255.255.255 area 0
R4(config-router)#network 14.0.0.0 0.0.0.255 area  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 2.2.2.2, 00:28:48, Serial3/1
O     10.0.0.0/8 [110/65] via 1.1.1.1, 00:31:39, Serial3/0
      14.0.0.0/32 is subnetted, 1 subnets
O IA     14.0.0.1 [110/129] via 2.2.2.2, 00:26:24, Serial3/1
O     30.0.0.0/8 [110/65] via 2.2.2.2, 00:29:55, Serial3/1
O IA  40.0.0.0/8 [110/129] via 2.2.2.2, 00:26:39, Serial3/1


R3#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     1.0.0.0/8 [110/128] via 2.2.2.1, 00:29:41, Serial3/1
O     10.0.0.0/8 [110/129] via 2.2.2.1, 00:29:41, Serial3/1
      14.0.0.0/32 is subnetted, 1 subnets
O        14.0.0.1 [110/65] via 3.3.3.2, 00:27:06, Serial3/2
O     20.0.0.0/8 [110/65] via 2.2.2.1, 00:29:41, Serial3/1
O     40.0.0.0/8 [110/65] via 3.3.3.2, 00:27:21, Serial3/2

R4#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  1.0.0.0/8 [110/192] via 3.3.3.1, 00:28:06, Serial3/2
O IA  2.0.0.0/8 [110/128] via 3.3.3.1, 00:28:06, Serial3/2
O IA  10.0.0.0/8 [110/193] via 3.3.3.1, 00:28:06, Serial3/2
O IA  20.0.0.0/8 [110/129] via 3.3.3.1, 00:28:06, Serial3/2
O IA  30.0.0.0/8 [110/65] via 3.3.3.1, 00:28:06, Serial3/2

No routes from 11.0.0.0 coming in to routing table  of R2, R3, R3, and R4 as it belong to area 10 which in not directly connected to area 0

in order to make sure that the loopback of R1 (11.0.0.0) routes should be seen on all the other routes we need to configure Virtual-link which allows area 10 to area 0 virtually over area 20 virtual area.

R1#show ip protocols
*** IP Routing is NSF aware ***

Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 11.1.1.1
  Number of areas in this router is 2. 2 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    1.0.0.0 0.255.255.255 area 20
    10.0.0.0 0.255.255.255 area 20
    11.0.0.0 0.0.0.255 area 10
  Routing Information Sources:
    Gateway         Distance      Last Update
    22.1.1.1             110      00:37:30
    33.1.1.1             110      00:32:35
  Distance: (default is 110)



R3#show ip protocols
*** IP Routing is NSF aware ***

Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 33.1.1.1
  It is an area border router
  Number of areas in this router is 2. 2 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    2.0.0.0 0.255.255.255 area 20
    3.0.0.0 0.255.255.255 area 0
    30.0.0.0 0.255.255.255 area 20
  Routing Information Sources:
    Gateway         Distance      Last Update
    11.1.1.1             110      00:35:57
    14.0.3.1             110      00:33:22
    22.1.1.1             110      00:35:57
  Distance: (default is 110)

R1(config)#router ospf 1
R1(config-router)#area 20 virtual-link 33.1.1.1

R3(config)#router ospf 1
R3(config-router)#area 20 virtual-link 11.1.1.1

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 2.2.2.2, 00:40:25, Serial3/1
O     10.0.0.0/8 [110/65] via 1.1.1.1, 00:43:16, Serial3/0
      11.0.0.0/32 is subnetted, 1 subnets
O IA     11.0.0.1 [110/65] via 1.1.1.1, 00:02:47, Serial3/0
      14.0.0.0/32 is subnetted, 1 subnets
O IA     14.0.0.1 [110/129] via 2.2.2.2, 00:38:01, Serial3/1
O     30.0.0.0/8 [110/65] via 2.2.2.2, 00:41:32, Serial3/1
O IA  40.0.0.0/8 [110/129] via 2.2.2.2, 00:38:16, Serial3/1


R3#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     1.0.0.0/8 [110/128] via 2.2.2.1, 00:41:43, Serial3/1
O     10.0.0.0/8 [110/129] via 2.2.2.1, 00:41:43, Serial3/1
      11.0.0.0/32 is subnetted, 1 subnets
O IA     11.0.0.1 [110/129] via 2.2.2.1, 00:03:18, Serial3/1
      14.0.0.0/32 is subnetted, 1 subnets
O        14.0.0.1 [110/65] via 3.3.3.2, 00:39:08, Serial3/2
O     20.0.0.0/8 [110/65] via 2.2.2.1, 00:41:43, Serial3/1
O     40.0.0.0/8 [110/65] via 3.3.3.2, 00:39:23, Serial3/2

R4#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  1.0.0.0/8 [110/192] via 3.3.3.1, 00:40:10, Serial3/2
O IA  2.0.0.0/8 [110/128] via 3.3.3.1, 00:40:10, Serial3/2
O IA  10.0.0.0/8 [110/193] via 3.3.3.1, 00:40:10, Serial3/2
      11.0.0.0/32 is subnetted, 1 subnets
O IA     11.0.0.1 [110/193] via 3.3.3.1, 00:03:35, Serial3/2
O IA  20.0.0.0/8 [110/129] via 3.3.3.1, 00:40:10, Serial3/2
O IA  30.0.0.0/8 [110/65] via 3.3.3.1, 00:40:10, Serial3/2


R1#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
33.1.1.1          0   FULL/  -           -        2.2.2.2         OSPF_VL0
22.1.1.1          0   FULL/  -        00:00:32    1.1.1.2         Serial3/0

R1#show ip ospf virtual-links
Virtual Link OSPF_VL0 to router 33.1.1.1 is up
  Run as demand circuit
  DoNotAge LSA allowed.
  Transit area 20, via interface Serial3/0
 Topology-MTID    Cost    Disabled     Shutdown      Topology Name
        0           128       no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:04
    Adjacency State FULL (Hello suppressed)
    Index 1/2, retransmission queue length 0, number of retransmission 0
    First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
    Last retransmission scan length is 0, maximum is 0
    Last retransmission scan time is 0 msec, maximum is 0 msec

R4#ping 11.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 11.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 80/131/172 ms





 


 


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Wednesday, 7 November 2018

Route Redistribution


Route redistribution 
 when we take a route from one routing protocol and inject that route or distribute it into another routing protocol.  Routers by default only advertise and share routing information with other routers running the same protocol and in a same AS. If you have 2 routers and one runs EIGRP and the other runs OSPF and you want them to know about each other’s routes, by default, router do not share routes information because they are not running the same protocol. Here we need redistribution.

In short- Redistribution is the process of exchanging routing information between different routing protocols.

You can use redistribution when using multiple protocols, migrating to a more advance routing, you can use redistribution if you having mismatch between devices (vendors) or political boundaries.

Note: internal routes are routes advertised within the same protocol.
          External routes are routes which get redistributed.

To configure redistribution
Router must be running both protocols

Change metric.
RIPv2:   HOP COUNTS
OSPF:   COST
EIGRP:  BW + DELAY + LOAD + MTU + RELIABILITY

Configuration redistribution between RIP and EIGRP


Topology:



 GOAL: 
  • configure the interfaces as per the topology, advertise the interfaces with the same protocols defined as per the topology.
  • configure Redistribution on R2 and make sure the R1 and R3 exchange the routes using redistribution.



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
Serial3/1              2.2.2.1         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              2.2.2.2         YES manual up                    up

R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#network 10.0.0.0
R1(config-router)#network 1.0.0.0
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

R2(config)#router eigrp 100
R2(config-router)#network 2.0.0.0
R2(config-router)#no auto-summary
R2(config-router)#end

R3(config)#router eigrp 100
R3(config-router)#network 30.0.0.0
R3(config-router)#network 2.0.0.0
R3(config-router)#no auto-summary
R3(config-router)#end

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, 00:00:15, Serial3/0

R3#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

      2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        2.0.0.0/8 is directly connected, Serial3/1
L        2.2.2.2/32 is directly connected, Serial3/1
      30.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        30.0.0.0/8 is directly connected, FastEthernet0/0
L        30.1.1.1/32 is directly connected, FastEthernet0/0

R2#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        1.1.1.2/32 is directly connected, Serial3/0
      2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        2.0.0.0/8 is directly connected, Serial3/1
L        2.2.2.1/32 is directly connected, Serial3/1
R     10.0.0.0/8 [120/1] via 1.1.1.1, 00:00:08, 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
D     30.0.0.0/8 [90/2172416] via 2.2.2.2, 00:02:49, Serial3/1

  • The above outputs you can see R2 learn thee routes from R1 and R3 (10.0.0.0 and 30.0.0.0) networks respectively but R1 and R3 can't  exchange their routes, the reason is both routers running different routing protocols, we need to configure redistribution on router 2 because router is running both the protocol. 

R2(config)#router rip
R2(config-router)#redistribute eigrp 100 metric 5
R2(config-router)#exit

R2(config)#router eigrp 100
R2(config-router)#redistribute rip metric 1000 2000 255 100 1500
R2(config-router)#exit

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
R     2.0.0.0/8 [120/5] via 1.1.1.2, 00:00:09, 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, 00:00:09, Serial3/0
R     30.0.0.0/8 [120/5] via 1.1.1.2, 00:00:09, Serial3/0

R3#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

D EX  1.0.0.0/8 [170/3584000] via 2.2.2.1, 00:03:04, Serial3/1
      2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        2.0.0.0/8 is directly connected, Serial3/1
L        2.2.2.2/32 is directly connected, Serial3/1
D EX  10.0.0.0/8 [170/3584000] via 2.2.2.1, 00:03:04, Serial3/1
D EX  20.0.0.0/8 [170/3584000] via 2.2.2.1, 00:03:04, Serial3/1
      30.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        30.0.0.0/8 is directly connected, FastEthernet0/0
L        30.1.1.1/32 is directly connected, FastEthernet0/0

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OSPF Neighbor states


OSPF neighbor states



During the OSPF adjacency formation process, two OSPF routers transition through several states, which include:




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  1. Down-  first OSPF neighbor state in this state no information (hello) has been received from the neighbouring router but in the down state hello packets can be sent to the neighbor.
  2. Attempt- this state is only valid for manually configured neighbor in an non broadcast multi-access (NBMA) environment. router send unicast hello packets every interval to the neighbor orm which hello's have not been received within the dead interval.
  3. Init-OSPF router recieved a hello packets from its neighbor but the receiving router's ID was not include in the hello packets.
Router ID (RID)- This is the highest active IP address on the router. Router ID is configured manually and dynamically if its not configured by the administrator, router choose the highest IP of the loopback interface is used and if loopback is not configured, Router choose the highest IP of physical interface.   

  Configure Router ID-

 R1(config)#router ospf 1
R1(config-router)#router-id ?
  A.B.C.D  OSPF router-id in IP address format
4. 2 WAY- 2 way state is attained when the router receiving the hello packets and router seen its own router ID within the received  hello packet. Bidirectional communication has been established. In the broadcast multi-access networks, an election can occur after this point.
5. Exstart- the actual process of exchanging link states information can start between the OSPF  routers. master/slave relationship is established and initial sequence numbers are exchange.




6.Exchange- In the Exchange state, OSPF routing information is exchanged using Database description (DBD or DD) packets and link-state request (LSR) and link state update (LSU) packets may also be sent. In this state OSPF router see what LSA's they have and what LSA's they do not have.

 7.Full- In the full state, all LSA's information is synchronized among neighbors and adjacency has been established. 

 %OSPF-5-ADJCHG: Process 1, Nbr 20.1.1.1 on Serial3/0 from LOADING to FULL, Loading Done


 R1#show ip ospf neighbor

 Neighbor ID     Pri   State           Dead Time   Address         Interface
20.1.1.1          0   FULL/  -        00:00:39    1.1.1.2         Serial3/0
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




















































































 


 


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