OSPF multiarea

Hello!

Revin dupa o scurta pauza in care m-am pregatit pentru finalizarea cursului Cisco IT Essentials.

Fiind un curs care a venit “la oferta” cu CCNA2, recunosc spre rusinea mea ca initial nu i-am acordat mare atentie si am avut o abordare superficiala vis-a-vis de el, avand impresia ca se discuta foarte mult despre notiuni pe care le stiu deja.

Totusi, fiind constient ca o gandire de genul “le stiu pe toate, nu mai am ce sa-nvat” este fundamental gresita, ducand la plafonare si ulterior degradare, am adoptat o atitudine mai pozitiva.

Dupa o parcurgere amanuntita a cursului si sustinerea examenului final, apreciez ca este un curs interesant care contine foarte multa informatie de actualitate. Il recomand celor care se gandesc la un job in IT.

Revenind la CCNA, laboratorul propus de data aceasta se adreseaza cursantilor CCNA3 si urmareste configurarea avansata a protocolului OSPF multiarea (pentru IPv4 si IPv6). Pentru a intelege laboratorul este necesara o recapitulare a capitolului 8 din CCNA2 si o parcurgere a capitolelor 5 si 6 din CCNA3.

In topologie vom avea o zona de backbone in care vom folosi trei imagini de 7200 si doua zone obisnuite in care vom folosi imagini de 3600 pentru a asigura accesul hosturilor la retea.

De routerul din area 1 vom lega desktop-ul fizic folosind un Loopback Adapter pentru a avea acces in topologie din commander. Routerele din area 2 vor fi legate intr-o retea de tip broadcast multiaccess si vom influenta alegerea unui DR si BDR prin modificarea prioritatilor pe interfete (255 pentru DR si 250 pentru BDR). Pe R2 si R3 vom configura interfete loopback pentru a simula LAN-urile.

Deoarece in backbone vom utiliza interfete gigabit, vom ajusta costul de referinta folosit de OSPF de la 100 la 1000. Vom configura intervalele la care se trimit mesajele de tip “hello” la 5 secunde, iar “dead-interval” la 20 de secunde.

Pentru ca mesajele schimbate de routere intre ele sa fie securizate, vom activa OSPF authentication folosind metoda Message Digest 5. Aceasta este metoda recomandata spre a fi utilizata, fiind cea mai sigura.

La recomandarea instructorului meu voi simula un scenariu des intalnit in practica, in care comunicarea dintre insule izolate de IPv6 se realizeaza prin interfete de tip tunnel peste retele de IPv4. Rutarea intre retelele configurate cu IPv6 o vom face folosind OSPFv3 multiarea. Vom plasa interfetele de tip tunnel in backbone iar interfetele loopback in area 1, respectiv area 2.

La final vom folosi comenzile de vizualizare pentru a verifica topologia sau pentru a face troubleshoot daca e cazul.

Laborator conceput de Adrian Roata (cursant InfoAcademy)

Elemente necesare:

GNS3 (www.gns3.com)

Imagini IOS : 7200 & 3600

Un Loopback Adapter configurat pe desktop-ul pe care rulam topologia

Surse suplimentare de informare :

cisco.com (configurarea IPv6 peste tuneluri IPv4)

Topologie (dati click pe imagine pentru a mari)

Configurare ASBR

ASBR#configure terminal

ASBR(config)#enable secret cisco

ASBR(config)#service password-encryption

ASBR(config)#banner motd #

Accesul neautorizat este interzis !

#

ASBR(config)#username admin privilege 15 secret cisco

ASBR(config)#line console 0

ASBR(config-line)#logging synchronous

ASBR(config-line)#no exec-timeout

ASBR(config-line)#login local

ASBR(config-line)#line vty 0 4

ASBR(config-line)#login local

* se repeta pe toate routerele din topologie

ASBR(config)#interface f0/0

ASBR(config-if)#ip address 192.168.255.221 255.255.255.240

ASBR(config-if)#description Link to ISP

ASBR(config-if)#no shutdown

ASBR(config-if)#interface g1/0

ASBR(config-if)#ip address 10.0.12.1 255.255.255.252

ASBR(config-if)#description Link to ABR1

ASBR(config-if)#no shutdown

ASBR(config-if)#interface s3/3

ASBR(config-if)#ip address 10.0.31.2 255.255.255.252

ASBR(config-if)#description Link to ABR2

ASBR(config-if)#no shutdown

ASBR(config)#ip route 0.0.0.0 0.0.0.0 192.168.255.209

ASBR(config)#router ospf 1

ASBR(config-router)#router-id 255.255.255.255

ASBR(config-router)#auto-cost reference-bandwidth 1000

*ajustam costul de referinta folosit de OSPF pentru a reflecta bandwidth-ul real al linkurilor

ASBR(config-router)#network 192.168.255.221 0.0.0.0 area 0

ASBR(config-router)#network 10.0.12.1 0.0.0.0 area 0

ASBR(config-router)#network 10.0.31.2 0.0.0.0 area 0

*anuntam retelele direct conectate identificand interfetele configurate pe router cu wildcard mask-ul 0.0.0.0. Protocolul OSPF stie in mod automat sa foloseasca masca de retea setata pe interfata, ca masca pentru reteaua anuntata.

ASBR(config-router)#passive-interface f0/0

*pasivizam interfata catre ISP pentru a nu trimite mesaje OSPF pe link.

ASBR(config-router)#default-information originate

ASBR(config-router)#area 0 authentication message-digest

*activam MD5 authentication pentru toate interfetele routerului plasate in backbone area

** MD5 authentication se poate configura global pentru toate interfetele routerului sau per interfata

ASBR(config)#interface g1/0

ASBR(config-if)#ip ospf hello-interval 5

ASBR(config-if)#ip ospf dead-interval 20

ASBR(config-if)#ip ospf message-digest-key 5 md5 cisco123

ASBR(config-if)#bandwidth 1000000

ASBR(config-if)#interface s3/3

ASBR(config-if)#ip ospf hello-interval 5

ASBR(config-if)#ip ospf dead-interval 20

ASBR(config-if)#ip ospf message-digest-key 5 md5 cisco123

ASBR(config)#access-list 1 permit any

ASBR(config)#ip nat inside source list 1 interface f0/0 overload

ASBR(config)#interface f0/0

ASBR(config-if)#ip nat outside

ASBR(config-if)#interface g1/0

ASBR(config-if)#ip nat inside

ASBR(config-if)#interface s3/3

ASBR(config-if)#ip nat inside

Configurare ABR1

ABR1(config)#interface g1/0

ABR1(config-if)#ip address 10.0.12.2 255.255.255.252

ABR1(config-if)#description Link to ASBR

ABR1(config-if)#no shutdown

ABR1(config-if)#interface g2/0

ABR1(config-if)#ip address 10.0.23.2 255.255.255.252

ABR1(config-if)#description Link to ABR2

ABR1(config-if)#no shutdown

ABR1(config-if)#interface f0/0

ABR1(config-if)#ip address 10.1.1.2 255.255.255.252

ABR1(config-if)#description Link to R1

ABR1(config-if)#no shutdown

ABR1(config)#router ospf 2

ABR1(config-router)#router-id 255.255.255.254

ABR1(config-router)#auto-cost reference-bandwidth 1000

ABR1(config-router)#network 10.0.12.2 0.0.0.0 area 0

ABR1(config-router)#network 10.0.23.2 0.0.0.0 area 0

ABR1(config-router)#network 10.1.1.2 0.0.0.0 area 1

ABR1(config-router)#area 0 authentication message-digest

ABR1(config-router)#area 1 authentication message-digest

ABR1(config)#interface g1/0

ABR1(config-if)#ip ospf hello-interval 5

ABR1(config-if)#ip ospf dead-interval 20

ABR1(config-if)#bandwidth 1000000

ABR1(config-if)#ip ospf message-digest-key 5 md5 cisco123

ABR1(config-if)#interface g2/0

ABR1(config-if)#ip ospf hello-interval 5

ABR1(config-if)#ip ospf dead-interval 20

ABR1(config-if)#bandwidth 1000000

ABR1(config-if)#ip ospf message-digest-key 5 md5 cisco123

ABR1(config-if)#interface f0/0

ABR1(config-if)#ip ospf hello-interval 5

ABR1(config-if)#ip ospf dead-interval 20

ABR1(config-if)#ip ospf message-digest-key 5 md5 cisco123

Configurare ABR2

ABR2(config)#interface g2/0

ABR2(config-if)#ip address 10.0.23.1 255.255.255.252

ABR2(config-if)#description Link to ABR1

ABR2(config-if)#no shutdown

ABR2(config-if)#interface s3/3

ABR2(config-if)#ip address 10.0.31.1 255.255.255.252

ABR2(config-if)#description Link to ASBR

ABR2(config-if)#no shutdown

ABR2(config-if)#interface f0/0

ABR2(config-if)#ip address 10.2.2.1 255.255.255.248

ABR2(config-if)#description Link to BMA network

ABR2(config-if)#no shutdown

ABR2(config)#router ospf 3

ABR2(config-router)#auto-cost reference-bandwidth 1000

ABR2(config-router)#network 10.0.23.1 0.0.0.0 area 0

ABR2(config-router)#network 10.0.31.1 0.0.0.0 area 0

ABR2(config-router)#network 10.2.2.1 0.0.0.0 area 2

ABR2(config-router)#area 0 authentication message-digest

ABR2(config-router)#area 2 authentication message-digest

ABR2(config)#interface g2/0

ABR2(config-if)#ip ospf hello-interval 5

ABR2(config-if)#ip ospf dead-interval 20

ABR2(config-if)#bandwidth 1000000

ABR2(config-if)#ip ospf message-digest-key 5 md5 cisco123

ABR2(config-router)#interface s3/3

ABR2(config-if)#ip ospf hello-interval 5

ABR2(config-if)#ip ospf dead-interval 20

ABR2(config-if)#ip ospf message-digest-key 5 md5 cisco123

ABR2(config-router)#interface f0/0

ABR2(config-if)#ip ospf hello-interval 5

ABR2(config-if)#ip ospf dead-interval 20

ABR2(config-if)#ip ospf message-digest-key 5 md5 cisco123

Configurare R1

R1(config)#interface f0/0

R1(config-if)#ip address 10.1.1.1 255.255.255.252

R1(config-if)#description Link to ABR1

R1(config-if)#no shutdown

R1(config-if)#interface f1/0

R1(config-if)#ip address 172.16.1.254 255.255.255.0

R1(config-if)#description LAN

R1(config-if)#no shutdown

R1(config)#router ospf 4

R1(config-router)#auto-cost reference-bandwidth 1000

R1(config-router)#network 10.1.1.1 0.0.0.0 area 1

R1(config-router)#network 172.16.1.254 0.0.0.0 area 1

R1(config-router)#area 1 authentication message-digest

R1(config)#interface f1/0

R1(config-if)#ip ospf hello-interval 5

R1(config-if)#ip ospf dead-interval 20

R1(config-if)#ip ospf message-digest-key 5 md5 cisco123

R1(config-if)#interface f0/0

R1(config-if)#ip ospf hello-interval 5

R1(config-if)#ip ospf dead-interval 20

R1(config-if)#ip ospf message-digest-key 5 md5 cisco123

R1(config)#ipv6 unicast-routing

R1(config)#interface tunnel 1

R1(config-if)#ipv6 address 2001:1337:b175:1::1/64

R1(config-if)#tunnel source f0/0

R1(config-if)#tunnel destination 10.2.2.3

R1(config-if)#tunnel mode ipv6ip

*configuram interfata tunnel 1

R1(config)#interface loopback 0

R1(config-if)#ipv6 address 2001:ad1:1::1/64

*configuram interfata loopback 0 pentru a simula un LAN configurat cu IPv6

R1(config)#ipv6 router ospf 6

R1(config-rtr)#router-id 255.255.255.1

R1(config-rtr)#interface tunnel 1

R1(config-if)#ipv6 ospf 6 area 0

R1(config-if)#interface lo 0

R1(config-if)#ipv6 ospf 6 area 1

*configuram OSPFv3 multiarea

Configurare R2

R2(config)#interface f0/0

R2(config-if)#ip address 10.2.2.2 255.255.255.248

R2(config-if)#description Link to ABR2

R2(config-if)#no shutdown

R2(config-if)#interface loopback 0

R2(config-if)#ip address 172.16.2.1 255.255.255.0

R2(config-if)#description LAN

R2(config-if)#no shutdown

R2(config)#router ospf 5

R2(config-router)#auto-cost reference-bandwidth 1000

R2(config-router)#network 10.2.2.2 0.0.0.0 area 2

R2(config-router)#network 172.16.2.1 0.0.0.0 area 2

R2(config-router)#area 2 authentication message-digest

R2(config)#interface f0/0

R2(config-if)#ip ospf hello-interval 5

R2(config-if)#ip ospf dead-interval 20

R2(config-if)#ip ospf priority 255

R2(config-if)#ip ospf message-digest-key 5 md5 cisco123

R2(config-if)#interface lo 0

R2(config-if)#ip ospf hello-interval 5

R2(config-if)#ip ospf dead-interval 20

R2(config-if)#ip ospf message-digest-key 5 md5 cisco123

Configurare R3

R3(config)#interface f0/0

R3(config-if)#ip address 10.2.2.3 255.255.255.252

R3(config-if)#description Link to ABR2

R3(config-if)#no shutdown

R3(config-if)#interface loopback 0

R3(config-if)#ip address 172.16.3.1 255.255.255.0

R3(config-if)#description LAN

R3(config-if)#no shutdown

R3(config)#router ospf 6

R3(config-router)#auto-cost reference-bandwidth 1000

R3(config-router)#network 10.2.2.3 0.0.0.0 area 2

R3(config-router)#network 172.16.3.1 0.0.0.0 area 2

R3(config-router)#area 3 authentication message-digest

R3(config)#interface f0/0

R3(config-if)#ip ospf hello-interval 5

R3(config-if)#ip ospf dead-interval 20

R3(config-if)#ip ospf priority 250

R3(config-if)#ip ospf message-digest-key 5 md5 cisco123

R3(config-if)#interface lo 0

R3(config-if)#ip ospf hello-interval 5

R3(config-if)#ip ospf dead-interval 20

R3(config-if)#ip ospf message-digest-key 5 md5 cisco123

R3(config)#ipv6 unicast-routing

R3(config)#interface tunnel 1

R3(config-if)#ipv6 address 2001:1337:b175:1::2/64

R3(config-if)#tunnel source f0/0

R3(config-if)#tunnel destination 10.1.1.1

R3(config-if)#tunnel mode ipv6ip

R3(config)#interface loopback 0

R3(config-if)#ipv6 address 2001:ad1:2::1/64

R3(config)#ipv6 router ospf 6

R3(config-rtr)#router-id 255.255.1.1

R3(config-rtr)#interface tunnel 1

R3(config-if)#ipv6 ospf 6 area 0

R3(config-if)#interface lo 0

R3(config-if)#ipv6 ospf 6 area 2

Verificare

#show ip interface brief

folosim aceasta comanda pentru a vizualiza daca am configurat corect IP-urile pe interfete

#show ip protocols

folosim aceasta comanda pentru a vizualiza ce retele anuntam, ce cost de referinta e folosit si ce interfete sunt pasive pe router, exemplu ASBR:

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 255.255.255.0

 It is an autonomous system boundary router

Redistributing External Routes from,

 Number of areas in this router is 1. 1 normal 0 stub 0 nssa

 Maximum path: 4

 Routing for Networks:

    10.0.12.1 0.0.0.0 area 0

    10.0.31.2 0.0.0.0 area 0

    192.168.255.221 0.0.0.0 area 0

 Passive Interface(s):

    FastEthernet0/0

 Routing Information Sources:

    Gateway         Distance      Last Update

    10.2.2.1             110      02:15:39

    255.255.254.0        110      02:16:30

 Distance: (default is 110)

#show ip ospf neighbor

folosim comanda aceasta pentru a vedea cu ce routere s-au format adiacente, prioritatea vecinilor pe interfete precum si starea in care se afla acestia (DR, BDR sau DROTHER) , exemplu ABR1:

Neighbor ID     Pri   State           Dead Time   Address         Interface

10.2.2.1          1   FULL/BDR        00:00:39    10.0.23.1       GigabitEthernet2/0

255.255.255.0     1   FULL/DR         00:00:34    10.0.12.1       GigabitEthernet1/0

1.1.1.1           1   FULL/BDR        00:00:35    10.1.1.1        FastEthernet0/0

#show ip route

verificam tabela de rutare, exemplu R1:

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

      D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

      N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

      E1 - OSPF external type 1, E2 - OSPF external type 2

      i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

      ia - IS-IS inter area, * - candidate default, U - per-user static route

      o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.1.1.2 to network 0.0.0.0

    172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks

C       172.16.1.0/24 is directly connected, FastEthernet1/0

O IA    172.16.3.1/32 [110/22] via 10.1.1.2, 01:39:43, FastEthernet0/0

O IA    172.16.2.1/32 [110/22] via 10.1.1.2, 01:39:43, FastEthernet0/0

    10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks

O IA    10.0.12.0/30 [110/11] via 10.1.1.2, 01:39:43, FastEthernet0/0

O IA    10.2.2.0/29 [110/21] via 10.1.1.2, 01:39:43, FastEthernet0/0

C       10.1.1.0/30 is directly connected, FastEthernet0/0

O IA    10.0.31.0/30 [110/658] via 10.1.1.2, 01:39:45, FastEthernet0/0

O IA    10.0.23.0/30 [110/11] via 10.1.1.2, 01:39:45, FastEthernet0/0

    192.168.255.0/28 is subnetted, 1 subnets

O IA    192.168.255.208 [110/21] via 10.1.1.2, 01:39:45, FastEthernet0/0

O*E2 0.0.0.0/0 [110/1] via 10.1.1.2, 01:39:45, FastEthernet0/0

#show ip ospf interface

folosim aceasta comanda pentru a verifica ce metoda de autentificare este folosita,  intervalele la care se trimit mesajele de tip “hello” si care e timpul dupa care un link e considerat “dead”

#clear ip ospf process

folosim aceasta comanda pentru a reinitializa adiacentele si pentru a influenta alegerea unui nou DR si BDR