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

OSPF neighbor states

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

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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.
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.
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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Tuesday, 6 November 2018

What is Stuck In Active (EIGRP)?

Stuck In Active (EIGRP)

The EIGRP convergence is the process when going active on a route is sometimes also by the name of the underlying algorithm, diffusing update algorithm (DUAL).

When a successor path is lost and there is no feasible successor is identified, the EIGRP router sends out queries on all interfaces in an attempt to identify an alternate path. EIGRP routers don’t select the successor until the EIGRP router receives a reply to all queries. When a router has received a reply for all its query messages, that router can safely use the best of the routes confirmed to be loop-free. The process can and does work well in many cases, often converging to a new route in less than 10 seconds. If a reply is missing for 3 minutes, the router becomes stuck in active (SIA). In that case, it reset the neighbor's relationship with the neighbors that did not reply to queries.

EIGRP sends every query and reply message using RTP, so every message is acknowledged using the EIGRP ACK message.

To limit the scope of queries, there are two tools: stub routers and route summarization this us to reduce the work performed by the DUAL and the scope of query messages.

EIGRP STUB

Stub routing is one way to limit queries. A stub router is one that is connected to more than two neighbors and should be a transit router. The EIGRP stub routing feature improves network stability, reduces resource utilization, and simplifies remote router (spoke) configuration. Stub routing is commonly used in a Hub-and-Spoke topology.

Here is the command:

R1(config-router)#EIGRP STUB?

connected Do advertise connected routes

leak-map Allow dynamic prefixes based on the leak-map

receive-only Set receive only neighbor

redistributed Do advertise redistributed routes

static Do advertise static routes

summary Do advertise summary routes

· Connected means the router advertises connected routes only for those interfaces that match with a network command.

· Leak-map means the router advertises only which is specified by a leak-map

· Receive-only means the router does not advertise any routes. This option can be used with any other option.

· Redistribution means the router advertises only the redistributed routes.

· Static means the router advertises only the static routes with redistributed static commands configured.

· Summary means the router advertises only auto-summarized or statically configured summary routes

NOTE: By default, is connected and summary.

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

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

1.Enhanced Interior Gateway Routing Protocol (EIGRP)

2.Stuck In Active (EIGRP)

3.EIGRP Equal-Cost and Unequal-Cost load balancing

4.Route filtering passive interface

5.Route summarization

6.EIGRP STUB and Configuration

7.Routing Protocol Authentication (EIGRP ) and configuration

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What is EIGRP Equal-Cost and Unequal-Cost load balancing? What is variance? How to configure?

EIGRP Equal-Cost and Unequal-Cost load balancing

Routes with the lowest metric get installed in the routing table by default, if two or more routes have the same metric the router will install both the routes in the routing table this is called equal cost load balancing.

EIGRP does equal cost load balancing automatically, whereas unequal cost load balancing is not automatic, for unequal cost load balancing we need to enable Variance. EIGRP can load balancing up to six paths, and the default is four paths.

The maximum number of paths are based on Cisco IOS versions and router platform. For the older Cisco IOS versions, the maximum-paths was 6. The latest version typically supports 16 or more.

R1 (config)#router eigrp 100

R1 (config-router)#maximum-paths ?

<1-32> Number of paths

Unequal cost load-balancing

EIGRP also supports unequal cost load balancing, it has to be done manually using variance. Variance is a multiplier value that ranges between (1 – 128) and the default is 1. The routes that can go for load balancing should satisfy the condition. The cost of the successor X variance > cost of the other routes to be used for load balancing

· The variance is multiplied by the current Feasible Distance.
· Any feasible successor whose calculated metric is less than or equal to the product of the variance and feasible distance is added to the IP routing table, assuming that the maximum-paths setting allows more routes
· Routes that are neither successor nor feasible successor routes can never add to the IP routing table, regardless of the variance setting.

Configuration of EIGRP Equal cost load balancing-

Topology:

Configure the topology as per the diagram
Advertise the interfaces using EIGRP 100
Ensure the load balancing via traceroute.

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

Serial3/3 4.4.4.2 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

FastEthernet1/0 unassigned YES unset administratively down down

FastEthernet1/1 unassigned YES unset administratively down down

GigabitEthernet2/0 unassigned YES unset administratively down down

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

FastEthernet1/0 unassigned YES unset administratively down down

FastEthernet1/1 unassigned YES unset administratively down down

GigabitEthernet2/0 unassigned YES unset administratively down down

Serial3/0 unassigned YES unset administratively down down

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

Serial3/3 4.4.4.1 YES manual up up

R1(config)#router eigrp 100

R1(config-router)#network 1.0.0.0

R1(config-router)#network 4.0.0.0

R1(config-router)#network 10.0.0.0

R1(config-router)#no auto-summary

R2(config)#router eigrp 100

R2(config-router)#network 20.0.0.0

R2(config-router)#network 1.0.0.0

R2(config-router)#network 2.0.0.0

R2(config-router)#no auto-summary

R3(config)#router eigrp 100

R3(config-router)#network 30.0.0.0

R3(config-router)#network 2.0.0.0

R3(config-router)#network 3.0.0.0

R3(config-router)#no auto-summary

R4(config)#router eigrp 100

R4(config-router)#network 4.0.0.0

R4(config-router)#network 3.0.0.0

R4(config-router)#network 40.0.0.0

R4(config-router)#no auto-summary

R1#show ip eigrp 100 neighbors

EIGRP-IPv4 Neighbors for AS(100)

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

1 4.4.4.1 Se3/3 12 00:15:50 37 222 0 8

0 1.1.1.2 Se3/0 13 00:17:52 67 402 0 20

R3#show ip eigrp neighbors

EIGRP-IPv4 Neighbors for AS(100)

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

1 3.3.3.2 Se3/2 12 00:17:17 41 246 0 9

0 2.2.2.1 Se3/1 11 00:17:45 48 288 0 19

R1#show ip route eigrp

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 2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:17:19, Serial3/0

D 3.0.0.0/8 [90/2681856] via 4.4.4.1, 00:17:19, Serial3/3

D 20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:17:19, Serial3/0

D 30.0.0.0/8 [90/2684416] via 4.4.4.1, 00:17:19, Serial3/3

[90/2684416] via 1.1.1.2, 00:17:19, Serial3/0

D 40.0.0.0/8 [90/2172416] via 4.4.4.1, 00:17:19, Serial3/3

The above output you can see that the router R1 installed both routes in the routing table as it is using both the routes to reach the network 30.1.1.1.

R1#show ip eigrp topology

EIGRP-IPv4 Topology Table for AS(100)/ID(10.1.1.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

r - reply Status, s - sia Status

P 2.0.0.0/8, 1 successors, FD is 2681856

via 1.1.1.2 (2681856/2169856), Serial3/0

P 4.0.0.0/8, 1 successors, FD is 2169856

via Connected, Serial3/3

P 10.0.0.0/8, 1 successors, FD is 28160

via Connected, FastEthernet0/0

P 30.0.0.0/8, 2 successors, FD is 2684416

via 1.1.1.2 (2684416/2172416), Serial3/0

via 4.4.4.1 (2684416/2172416), Serial3/3

P 3.0.0.0/8, 1 successors, FD is 2681856

via 4.4.4.1 (2681856/2169856), Serial3/3

P 40.0.0.0/8, 1 successors, FD is 2172416

via 4.4.4.1 (2172416/28160), Serial3/3

P 1.0.0.0/8, 1 successors, FD is 2169856

via Connected, Serial3/0

P 20.0.0.0/8, 1 successors, FD is 2172416

via 1.1.1.2 (2172416/28160), Serial3/0

R1#traceroute 30.1.1.1

Type escape sequence to abort.

Tracing the route to 30.1.1.1

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

1 1.1.1.2 76 msec

4.4.4.1 112 msec

1.1.1.2 52 msec

2 3.3.3.1 100 msec

2.2.2.2 68 msec

3.3.3.1 48 msec

now R1 is doing equal cost load balancing vea R2 and R4 because both the routes are having equal cost to reach network 30.1.1.1

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Thursday, 8 November 2018

OSPF Virtual Link

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LINKEDIN

Wednesday, 7 November 2018

Route Redistribution

OSPF Neighbor states

OSPF neighbor states

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Tuesday, 6 November 2018

What is Stuck In Active (EIGRP)?

Stuck In Active (EIGRP)

EIGRP STUB

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What is EIGRP Equal-Cost and Unequal-Cost load balancing? What is variance? How to configure?

EIGRP Equal-Cost and Unequal-Cost load balancing

Unequal cost load-balancing

Configuration of EIGRP Equal cost load balancing-

Topology:

What is BGP Allowas-in Feature? How to configure BGP Allowas-in? GNS3