NXLD43 OSPF open shortest path first part III kho tài liệu bách khoa

OSPF Open Shortest Path First Part- IIIR6 config-router #network 0.0.0.0 R7 config-if #router ei 200 R7 config-router #no auto-summary R7 config-router #network 0.0.0.0 R3#sh ip route No

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OSPF (Open Shortest Path First) Part- III Topology

R1 (config) #int fa0/0

R1 (config-if) #ip add 192.168.101.1 255.255.255.0

R1 (config-if) #no shut

R1 (config) #int s0/0

R1 (config-if) #ip add 192.168.1.1 255.255.255.0

R2 (config-if) #ip add 192.168.102.1 255.255.255.0

R2 (config-if) #ip add 192.168.1.2 255.255.255.0

Figure 1 OSPF Topology

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OSPF (Open Shortest Path First) Part- III

R2 (config-if) #ip add 192.168.2.1 255.255.255.0

R3 (config) #int f0/0

R3 (config-if) #ip add 192.168.103.1 255.255.255.0

R3 (config-if) #ip add 192.168.2.2 255.255.255.0

R3 (config-if) #ip add 192.168.3.1 255.255.255.0

R3 (config-if) #ip add 192.168.6.1 255.255.255.0

R3 (config-if) #ip add 101.1.1.100 255.255.255.0

R4 (config-if) #ip add 192.168.104.1 255.255.255.0

R4 (config-if) #ip add 192.168.3.2 255.255.255.0

R4 (config-if) #ip add 192.168.4.1 255.255.255.0

R5 (config-if) #ip add 192.168.105.1 255.255.255.0

R5 (config-if) #ip add 192.168.4.2 255.255.255.0

R5 (config-if) #ip add 192.168.5.1 255.255.255.0

R6 (config-if) #ip add 192.168.106.1 255.255.255.0

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R6 (config-if) #ip add 192.168.5.2 255.255.255.0

R6 (config) #int loo 1

R6 (config-if) #ip add 172.60.1.1 255.255.255.0

R6 (config-if) #ip add 172.60.2.1 255.255.255.0

R6 (config-if) #ip add 172.60.3.1 255.255.255.0

R6 (config-if) #ip add 172.60.4.1 255.255.255.0

R6 (config-if) #ip add 172.60.5.1 255.255.255.0

R7 (config-if) #ip add 192.168.107.1 255.255.255.0

R7 (config-if) #ip add 192.168.6.2 255.255.255.0

R7 (config-if) #ip add 172.70.1.1 255.255.255.0

R7 (config-if) #ip add 172.70.2.1 255.255.255.0

R7 (config-if) #ip add 172.70.3.1 255.255.255.0

R7 (config-if) #ip add 172.70.4.1 255.255.255.0

R7 (config-if) #ip add 172.70.5.1 255.255.255.0

R7#ping 192.168.6.1

Successful

ISP (config) #int fa0/0

ISP (config-if) #ip add 102.1.1.1 255.255.255.0

ISP (config-if) #no shut

ISP (config) #int s0/0

ISP (config-if) #ip add 101.1.1.1 255.255.255.0

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ISP (config-if) #no shut

OSPF Configuration

R1 (config-if) #ip os 100 area 1

R3 (config-if) #router ei 100

R3 (config-router) #no auto-summary

R3 (config-router) #network 192.168.6.0

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R3#sh ip route

Now we want to communicate OSPF domain with ei 100 domain

For that we will perform here redistribution

R3 (config) #router os 100

R3 (config-router) #redistribute ei 100 subnets metric-type 1

R3 (config-router) #router ei 100

R3 (config-router) #redistribute os 100 metric 1 1 1 1 1

We performed here two way of redistribution

R1#ping 172.70.1.1 source fa0/0

Successful

R1#sh ip route os

Here we can see two types of routes

First is intra area (which belongs to its area)

OIA means Inter area

E – External Area

Now our task is configure area 1 is as stub

R1 (config-router) #area 1 stub

Requirements for stub area

1 Virtual links are not allowed

2 Area 0 can’t be stub

3 All the routers must be agree that we are a part of stub area If you are configuring R1, that area

1 is stub so it is your duty you have to configure R2 that area 1 is stub, if you will not configure, neighborship will not established

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R1#sh ip route os

Successful

R2 #sh ip route

It contains entire ospf routes

Now we will see totally stub, it filters the external routes and inter area routes, and places them as a default route

R2 (config) #area 1 stub no-summary

R1#sh ip route os

We can see small routing table here

R5#sh ip route os

R4 (config-router) #area 2 stub no-summary

R5#sh ip route os

R5#ping 192.168.101.1 source s0/0

successful

Now we will perform redistribution on R5

R5 (config-router) #redistribute ei 200 subnets metric-type 1

R5 (config) #router ei 200

R5 (config-router) #redistribute os 100 metric 1 1 1 1 1

R3#sh ip route

Here we cannot see 172.60.0.0 routes

Now we will configure NSSA

First we need to remove this command here

R4 (config-router) #no area 2 stub

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If we will remove stub command totally stub command will removed automatically

R4 (config-router) #area 2 nssa

R5 (config-router) #area 2 nssa

R3#sh ip route

Here we can see

O E 1 – 172.60.1.0 to 5

R7#sh ip route ei

Here we can see this route 172.60.1.0 to 5

R4#sh ip route os

It contain 70 series here 172.70.0.0

R5#sh ip route os

It doesn’t contain the route of 172.70.0.0

R5#ping 172.70.1.1

not successful

Now we will configure Totally NSSA on R4

R4 (config-router) #area 2 nssa no-summary default-information-originate

R5#ping 172.70.1.1

successful

R6#ping 172.70.1.1

successful

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OSPF (Open Shortest Path First) Part- III Now we will remove stub and totally stub from area 1

Now here we will provide the internet access on all routers

R3 is directly connected with the ISP router

R3#ping 101.1.1.1 successful

R3#ping 102.1.1.1 not successful

Now we will create default route on R3 towards ISP

R3 (config) #Ip route 0.0.0.0 0.0.0.0 101.1.1.1

Here R3 is able to communicate with the ISP

not successful

R3 (config-if) #ip nat inside

R3 (config-if-nat) #int s0/1

R3 (config-if) #ip nat outside

R3 (config-if-nat) #int f0/0

R3 (config) #access-list 10 permit any

R3 (config-access) #ip nat inside source list 10 int s0/3 overload

R3#ping 102.1.1.1 source fa0/0 successful

R3#sh ip nat translation

Now we will provide the internet access to all areas

R2#sh ip route

It hasn’t any default route so it can’t communicate with the internet

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R3 (config-router) #default-information originate always

R2 #sh ip route

Here we can see a default route O*E2 0.0.0.0/0

R1#piing 102.1.1.1 source fa0/0 successful

R6#ping 102.1.1.1 source loo1 successful

R7#ping 102.1.1.1 source loo1 not successful

R7#sh ip route

It doesn’t contain default route

R3 (config) #ip summary-address ei 100 0.0.0.0 0.0.0.0

R3#sh ip route

D* 0.0.0.0 / 0

Now we can see here default route

R7#ping 102.1.1.1 source loo 1

successful

There are three ways to generate default route in Eigrp

1 Redistribution

2 Summarization

3 IP default network

Now here we will check LSAs

R1#sh ip ospf database

Router LSA contains router ID of a router It is sent within an area

Router ID

(i) Highest Loop Back

(ii) Highest Up Physical int IP

(iii) Router ID

Here we can see two router ID

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192.168.101.1

192.168.102.1

It contains DR router ID and it is sent by DR

DR & BDR are elected only in Broadcast and non-broadcast multi-access network

We have point to point link, so DR and BDR is not available

We will make forcefully it broadcast segment via command

R1 (config-if) #ip os network broadcast

R2 (config-if) #ip os network broadcast

R1#sh ip os neighbor

R1#debug ip os adj

R1#clear ip os process

Yes

R1#un all

We can see first is Down state Attempt state only happens in frame-realy To check init we need to go

on R2

R2#debug ip os adj

R2#clear ip process

Yes

R2#un all

Here we can see init

Contain DR ID

For DR

(i) Highest router Priority

(ii) Highest router ID

Router 2 is DR here

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When a route of one area goes to another area they go as summary SLA It is sent by ABR

Here R2 is ABR

It contains ASBR router ID & it is sent by ABR

R3 is ASBR here

 External LSA

It contains External routes It is sent by ASBR

172.70 series sending R3

172.60 series sending R4

 Group Membership LSA – It is not supported by cisco

 NSSA– It allows an ASBR to send external area through stub area to backbone area using LSA 7

R5#sh ip os database

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