ospf pract

7/31/2019 Ospf Pract

1/114

Practica: Protocolos de Enrutamiento de Estado de Enlace

Andres Barbieri *

16 de mayo de 2008

1. Introduccion

En este documento se ven ejemplos del protocolo de Enrutamiento de Estado de Enlace intra-ASmas utilizado sobre redes IP, OSPF (Open Shortest Path First). Se ver a OSPF estandar mas algunascaractersticas extras usadas por fabircantes como cisco. La Internet Engineering Task Force (IETF) en1988 reconociendo las carencias de RIP formo un grupo para desarrollar un protocolo nuevo, OSPF, laprimera RFC surgio en 1989.

1.1. Caractersticas de Protocolos de Estado de Enlace

Los protocolos de LS (Estado de Enalce, Link State) se caracterizan por:

Todos los nodos comparten toda la informacion con todos, as se logra que todos tengan una imagen

comun y coherente de la red.

Una vez que todos tienen la imagen de la red ejecutan un algoritmo centralizado por ejemplo el deDijkstra -SFP-, sobre esta, observando la red como un grafo dirigido. Lo ejecutan para cada destinoposible partiendo del mismo nodo.

No hay intercambio de toda la informacion (tabla de enrutamiento) de forma periodica, solo seinforman cambios, actualizaciones y se lanzan paquetes para testear los enlaces.

El algoritmo tiene un alto consumo de bandwidth al principio, hasta que converge pero luego esmnimo. A diferencia de los de DV que se mantiene bastante constante.

Ven la topologa de la red completa en cada nodo.

Debido a esto tiene las siguientes consecuencias:

Convergencia mas rapida, mas facil de detectar nuevos caminos y descartar lazos.

No son propensos a lazos (LOOPLESS).

Requieren mas memoria y capacidad de procesamiento porque deben almacenar la informa-cion de la red completa, y para cada destino, cada nodo, debe corre el algoritmo de formaindependiente.

Ejemplos de este tipo de protocolos de enrutamiento son:

OSPF (IGP).

IS-IS (IGP).

*[email protected]

1


2/114

Universidad Nacional de La Plata

1.2. Equipamiento para Practicas

Las configuraciones y tests se realizan sobre routers cisco 2600:

2003>show version

Cisco Internetwork Operating System Software

IOS (tm) C2600 Software (C2600-JK8S-M), Version 12.2(12c), RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2003 by cisco Systems, Inc.

Compiled Wed 05-Feb-03 16:36 by kellythw

Image text-base: 0x8000808C, data-base: 0x8156F2AC

ROM: System Bootstrap, Version 12.2(7r) [cmong 7r], RELEASE SOFTWARE (fc1)

uno uptime is 3 weeks, 3 hours, 46 minutes

System returned to ROM by power-onSystem image file is "flash:c2600-jk8s-mz.122-12c.bin"

cisco 2620XM (MPC860P) processor (revision 0x100) with 94208K/4096K bytes of memory.

Processor board ID JAE073505T5 (657130552)

M860 processor: part number 5, mask 2

Bridging software.

X.25 software, Version 3.0.0.

SuperLAT software (copyright 1990 by Meridian Technology Corp).

TN3270 Emulation software.

Basic Rate ISDN software, Version 1.1.

1 FastEthernet/IEEE 802.3 interface(s)2 Low-speed serial(sync/async) network interface(s)

1 ISDN Basic Rate interface(s)

32K bytes of non-volatile configuration memory.

32768K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

Se conectaron los routers mediante cables V.35-SmartSerial o V.35-D60 cruzados de forma back toback, sin CSU/DSUs al medio. Tambien mediante Ethernet utilizando cables UTP Cat5 para 100BaseTX.En los graficos, por ejemplo la figura 3 las loopback se marcan como /32 pero no se configuran de esaforma.

Es valido para las practicas y tambien se uso en este caso el simulador DYNAMIPS sobre la plataformaPC+GNU/Linux.

2. OSPF (Open Shortest Path First)

OSPF es un protocolo definido por [RFC-2328] par IPv4 y por [RFC-2740] para IPv6. La evolucionde OSPF brevemente fue la siguiente: La [RFC-1247] define OSPFv1. La [RFC-1583], [RFC-2178], y[RFC-2328] son la evolucion a OSPFv2. Definen las posibilidad de ejecutar en multiples areas y cinco (5)Tipos de LSA basicos. La [RFC-1584] define MOSPF (OSPF para arboles Multicast) y el tipo de LSA 6(Multicast Extensions to OSPF). La [RFC-1587] agrega NSSAs y el tipo de LSA 7.

2.1. Caractersticas de OSPF

Las caractersticas principales de OSPF son:

2


3/114


4/114


Es un protocolo Classless (enva la mascara) con las actualizaciones.

Utiliza varios tipos de mensajes y varias etapas:

Protocolo Hello: Se utiliza para descubrir a los vecinos y para detectar fallas de enlace. Se da debaja la vecindad luego del Dead Interval. Los mensajes son Hello y se envan periodicamente.En el descubrimiento de los vecinos se pasa por varios estados, algunos son:

Down no se a recibido informacion.

Init se vio un Hello desde un vecino, pero el router mismo no se vio reflejado en el mismo(One-Way).

2Way se vio un Hello desde un vecino, y el router se vio as mismo en el contenido delmismo. A esta altura se establecio la Vecindad. Al final ya se ha elegido DR y BDR.

Exstart Se intenta establecer un numero de secuencia y una relacion master/slave paraintercambiar informacion. Se intercambian los LS DBD (Descriptores).

Exchange se envan las LS DBs (Link State Database) entre los vecinos. Se realiza deacuerdo a la etapa anterior.

Loading se termina el intercambio, ya pueden responder a Request o realizarlos.

Full la Adyacencia se establecio, deberan tener la misma LS DBs.

Protocolo del Eleccion del DR: Forma parte del Hello. Usado en redes multi-acceso, paraahorrar BW. Mas adelante se ve en detalle.

Protocolo Exchange: Se utiliza para realizar la sincronizacion de las LS DBs en una etapa ini-cial. Luego se mantiene con Flooding. Se ejecuta luego que los vecinos est an en el estado2WAY. Se envan DBD (Descriptores de la Database) y se confiraman (Acks) en relacionmaster/slave. Se utilizan los bits I (init), M(more) y MS(master/slave), el master ser a el quegenere el numero de secuencia mas grande (DD). Los Ack son LS DBD con el mismo DD queel master. Una vez que c/u tiene su lista de requerimiento envia LS Requests solicitandolos registros en los cuales esta interesado, los mismos son respondidos con LS Updates. Vercaptures/dr-bdr/ospf-dr-2003.pcap

Protocolo Flooding: Mantiene actualizada las LS DBs. Se ejecuta despues de los Exchanges.Los mensajes que se utilizan se llaman LSA (Link State Advertisments), LSA Updatey LSA ACK.

Es un protocolo completo y escalable pero es bastante complejo de configurar y administrar enredes grandes.

2.2. Tipos de Rutas OSPF

OSPF al ser un protocolo complejo permite diferenciar diferentes tipos de rutas.

Codigo en el Router Tipo de Ruta OSPF

O OSPF intra area.O IA OSPF inter area.O N1 OSPF NSSA external type 1.O N2 OSPF NSSA external type 2.

O E1 OSPF external type 1.O E2 OSPF external type 2.

Cuadro 1: Tabla de tipos de rutas OSPF segun cisco.


5/114


2.2.1. Rutas intra-Area OSPF

Son rutas aprendidas desde routers que se encuentran en la misma area.

2.2.2. Rutas inter-Area OSPF

Son rutas aprendidas desde routers que se encuentran en otras area. En realidad los routers quelas ensenan son los que se conocen como ABR (Area Border Routers), routers que tiene interfaces endiferentes areas.

2.2.3. Rutas Externas OSPF

Son rutas generadas por ASBR (Autonomous System Border Router). A continuacion se transcribe

las descripciones de las rutas externas de textos de la bibliografa presentada al final:...E1 vs. E2 External Routes: External routes fall under two categories, external type 1 and external type2. The difference between the two is in the way the cost (metric) of the route is being calculated. Thecost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route. Atype 1 cost is the addition of the external cost and the internal cost used to reach that route. A type 1route is always preferred over a type 2 route for the same destination.With type 2 being the default. A type 1 route has a metric that is the sum of the internal OSPF cost andthe external redistributed cost. A type 2 route has a metric equal only to the redistributed cost. If routesare redistributed into OSPF as type 2 then every router in the OSPF domain will see the same cost toreach the external networks. If routes are redistributed into OSPF as type 1, then the cost to reach theexternal networks could vary from router to router.

Route redistribution is the process of taking routes learned via one routing protocol and injecting thoseroutes into another routing domain. (Static and connected routes can also be redistributed.) When arouter running OSPF takes routes learned by another routing protocol and makes them available tothe other OSPF-enabled routers its communicating with, that router becomes an Autonomous SystemBorder Router (ASBR).E2 is the default route type for routes learned via redistribution. The key with E2 routes is that the costof these routes reflects only the cost of the path from the ASBR to the final destination the cost of thepath ... is not reflected in this cost. (Remember that OSPFs metric for a path is referred to as cost.)...

# redistribute static subnets metric 20

In this example, we want the cost of the routes to reflect the entire path, not just the path betweenthe ASBR and the destination network. To do so, the routes must be redistributed into OSPF as E1routes on the ASBR, as shown here.

# redistribute rip subnets metric-type 1

Now the routes appear as E1 routes and have a larger metric, since the entire path cost is now reflectedin the routing table.

Knowing the difference between E1 and E2 routes is vital for fully understanding a production routersrouting table.

2.2.4. Rutas NSSA OSPF

Las rutas NSSA son como las externas pero son inyectadas por ASBR de areas NSSA, areas stubespeciales, que pueden inyectar rutas externas. Estos links son traducidos a tipo 5 por los ABR de lasareas NSSA cuando salen de la misma. Dentro de la NSSA son de tipo 7.


6/114


2.3. OSPF Link Types (Tipo de Links)

Los tipos de LSA (Link State Advertisments) L1 al L5 fueron definidos en la primera RFC, [RFC-1583].

Codigo de Link Descripcion en OSPF

L1 Router LinkL2 Network LinkL3 Summary Link (IP network)L4 Summary Link (Link to ABR)L5 External LinkL6 Group Membership Mcast. (MOSPF)L7 Type-7 AS External Link States

Cuadro 2: Tabla de tipos de LSA en OSPF.

A continuacion se describen y se transcribe las descripciones desde la bibliografa presentada.

2.3.1. L1: Router Links

Sumarizan todos los links vistos por el router origen/advertising. Todos los enlaces que posee el routerlocalmente. Router links advertisements are the Type 1 link state advertisements. Each router in an areaoriginates a router links advertisement. The advertisement describes the state and cost of the routerslinks (i.e., interfaces) to the area. All of the routers links to the area must be described in a single routerlinks advertisement. For details concerning the construction of router links advertisements. In router linksadvertisements, the Link State ID field is set to the routers OSPF Router ID.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| LS age | Options | 1 |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Link State ID |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Advertising Router |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| LS sequence number |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +| LS checksum | length |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| 0 |V |E |B | 0 | # links |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Link ID |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Link Data |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Type | # TOS | metric |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| ... |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +| TOS | 0 | TOS metric |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Link ID |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Link Data |


7/114


2.3.2. L2: Network Links

Advertidos por los DR a las redes BCAST, NBMA, describe a todos los router que est an adyacentes.Network links advertisements are the Type 2 link state advertisements. A network links advertisementis originated for each transit network in the area. A transit network is a multi-access network that hasmore than one attached router. The network links advertisement is originated by the networks DesignatedRouter. The advertisement describes all routers attached to the network, including the Designated Routeritself. The advertisements Link State ID field lists the IP interface address of the Designated Router.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| LS age | Options | 2 |+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Link State ID |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Advertising Router |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| LS sequence number |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| LS checksum | length |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Network Mask |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +

| Attached Router |

+ - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + - + -+ - + - + - + - + - + -+ - + - + - + - + - + -+ - +| ... |

2.3.3. L3, L4: Summary Links

No se sumarizan en un solo mensaje, todos los destinos individuales, cada uno en su mensaje.

L3 usado por ABR hacia la red (IP networks).

L4 usado por ABR hacia Routers de Borde (BR).

Summary link advertisements are the Type 3 and 4 link state advertisements. These advertisements are

originated by area border routers. A separate summary link advertisement is made for each destination(known to the router) which belongs to the AS, yet is outside the area. For details concerning theconstruction of summary link advertisements, see Section 12.4.3.Type 3 link state advertisements are used when the destination is an IP network. In this case theadvertisements Link State ID field is an IP network number (if necessary, the Link State ID can alsohave one or more of the networks host bits set; see Appendix F for details). When the destination isan AS boundary router, a Type 4 advertisement is used, and the Link State ID field is the AS boundaryrouters OSPF Router ID. (To see why it is necessary to advertise the location of each ASBR, consultSection 16.4.) Other than the difference in the Link State ID field, the format of Type 3 and 4 link stateadvertisements is identical.

2.3.4. L5: External Links

Generados desde los ASBR (Autonomous System Border Ruters). Los ASBR no necesariamente cor-ren BGP, son routers que corren otros protocolos de enrutamiento e inyectan rutas externas a OSPFaprendidas va estos protocolos. Por ejemplo rutas estaticas, RIP, BGP, u otros. No se sumarizan en unsolo mensaje, todos los destinos individuales. Transcribiendo:


8/114


...AS external link advertisements usually describe a particular external destination.AS external link advertisements are the Type 5 link state advertisements. These advertisements are orig-inated by AS boundary routers. A separate advertisement is made for each destination (known to therouter) which is external to the AS. For details concerning the construction of AS external link adver-tisements.AS external link advertisements usually describe a particular external destination. For these advertise-ments the Link State ID field specifies an IP network number (if necessary, the Link State ID can alsohave one or more of the networks host bits set; see Appendix F for details). AS external link advertise-ments are also used to describe a default route. Default routes are used when no specific route exists tothe destination. When describing a default route, the Link State ID is always set to DefaultDestination(0.0.0.0) and the Network Mask is set to 0.0.0.0.

2.3.5. L6: Group Membership Mcast Links

Type 6: Group membership link entry generated by multicast OSPF routers. Enhancements to OSPFVersion 2 to support IP multicast routing. Definidos en [RFC-1584] MOSPF.

2.3.6. L7: NSSA External Links

Definidos en [RFC-1587] The OSPF NSSA Option. Type 5 LSAs are not allowed in NSSA areas, sothe NSSA ASBR generates a type 7 LSA instead, which remains within the NSSA. This type 7 LSA getstranslated back into a type 5 by the NSSA ABR. Type 7: NSSA external routes generated by ASBR.Only flooded to the NSSA. The ABR converts LSA type 7 into LSA type 5 before flooding them into the

backbone (area 0). The ABR converts type 7 LSAs into type 5 LSAs, and propagates the type 5 LSAsinto normal areas.


9/114


3. OSPF Tipos de Redes y Ejemplos

OSPF define el protocolo para trabajar en redes clasificadas en 3 tipos o clases:

Redes Multi-acceso Broadcast (BCAST). Por ejemplo Ethernet/Token-Ring/FDDI.

Redes Multi-acceso Non-Broadcast (NBMA - Non-Broadcast Multi-access).Por ejemplo X.25/FrameRelay/ATM.

Redes Punto a Punto (P2P). Por ejemplo PPP/SLIP/HDLC.

Los tipos de Redes configurables en un router cisco son:

2003-R(config-if)#ip ospf network ?broadcast Specify OSPF broadcast multi-access network

non-broadcast Specify OSPF NBMA network

point-to-multipoint Specify OSPF point-to-multipoint network

point-to-point Specify OSPF point-to-point network.

El tipo de red Point-to-Multipoint esta contemplado en [RFC-2328]:...OSPF runs in one of two modes over non-broadcast networks. The first mode, called non-broadcastmulti-access or NBMA, simulates the operation of OSPF on a broadcast network. The second mode,called Point-to-MultiPoint, treats the non- broadcast network as a collection of point-to-point links...En ocasiones es necesario especificarlo explcitamente de acuerdo al comportamiento que se quiera lograr.

Esto es aplicable completamente a redes de tipo NBMA.

3.1. Routers Designados en OSPF

Router Designado (DR) y Designado de Backup (BDR) son elegidos en las dos redes Multi-access.Todo el intercambio de Updates se realiza contra el DR y BDR, luego el DR lo propaga a todos losvecinos par ahorrar bandwidth. Se transcribe de las referencias:...DR and BDR are elected for every multi-access network to optimize the adjacency building process.All the routers in that segment should be able to communicate directly with the DR and BDR for properadjacency (in the case of a point-to-point network, DR and BDR are not necessary since there are onlytwo routers in the segment, and hence the election does not take place)...

3.1.1. Descubrimiento de Vecinos en OSPF

Si existe soporte de broadcasts en la red OSPF se descubre de forma automatica a los vecinos, sinose debe configurar manualmente. Se transcribe desde las referencias:...In the broadcast multi-access Layer 2 topology, broadcasts are supported; therefore, a router thatruns OSPF can discover OSPF neighbors automatically and elect any router as DR and BDR since anydevice can talk to all other routers in that broadcast segment...In a point-to-point topology, neighbors are discovered automatically since neighbors are directly con-nected to each other through a point-to-point link, and broadcast or multicast packets are forwarded overthe network; however, the DR and BDR election does not take place as explained earlier.In an NBMA network topology, which is inherently nonbroadcast, neighbors are not discovered au-

tomatically. OSPF tries to elect a DR and a BDR due to the multi-access nature of the network, butthe election fails since neighbors are not discovered. Neighbors must be configured manually to overcomethese problems. Also, additional configuration is necessary in a hub and spoke topology to make sure thatthe hub routers, which have connectivity with every other spoke router, are elected as the DR and BDR.Alternatively, you can change the configuration on the NBMA interface to make OSPF believe that it isanother network type that does not have these problems. En [RFC-2328] se indica:


10/114


3.1.2. Timeout para Vecindad OSPF

La vecindad, o mejor las adyacencias, de mantienen con los mensajes Hello y se cae si luego de elDead Interval no se ven estos mensajes. Los tiempos de cada cuanto de envan estos mensajes y cuandose cae la adyacencia se configura para los diferentes tipos de redes de forma diferente.Los tiempos son descriptos para los diferentes tipos de redes en la tabla 3.1.2.

Network Type Hello (sec) Dead Interval (sec)

Point-to-Point 10 40Point-to-Multipoint 30 120

Broadcast 10 40Non-Broadcast 30 120

Cuadro 3: Tabla de tiempos de Hello y Dead Interval en OSPF.

3.2. Ejemplos sobre Ethernet, Broadcast

Ejemplos sobre Ethernet utilizando la toploga de la figura 1.

Figura 1: Topologa utilizada para la practica de OSPF Broadcast.

3.2.1. Configuraciones de los Routers

Router 2003

2003-R#show running-config

...

!

interface FastEthernet0/0ip address 172.17.4.3 255.255.255.0

duplex auto

speed auto

end

...


11/114


interface loopback 0

ip address 13.0.0.1 255.255.255.0

end

2003-R#show running-config | begin ospf 100

router ospf 100

log-adjacency-changes

network 13.0.0.0 0.0.0.255 area 0.0.0.3

network 172.17.4.0 0.0.0.255 area 0.0.0.0

!

Router 2004


...

!

interface FastEthernet0/0

ip address 172.17.4.4 255.255.255.0

duplex auto

speed auto

end

...


ip address 14.0.0.1 255.255.255.0end


router ospf 100


network 14.0.0.0 0.0.0.255 area 0.0.0.4

network 172.17.4.0 0.0.0.255 area 0.0.0.0

!

Router 2006

2006-R#show running-config...

!


ip address 172.17.4.6 255.255.255.0

duplex auto

speed auto

end

...


ip address 16.0.0.1 255.255.255.0

end


router ospf 100


network 16.0.0.0 0.0.0.255 area 0.0.0.6


12/114


network 172.17.4.0 0.0.0.255 area 0.0.0.0

!

3.2.2. Ver Routers DR y BDR

La eleccion se basa en la prioridad mas alta, por default todos en 1, 255 el mas grande y con 0 indicaque no quiere ser DR ni BDR. Si hay iguales prioridades desempata con el ID. Para seleccionar el ID lohace desde todas las direcciones IP de las loopbacks tomando la m as alta, si no tiene loopbacks seleccionala mas alta del resto. Necesita si o si una IP configurada para correr.

There must be at least one "up" IP interface, for OSPF to use as router ID

%OSPF-4-NORTRID: OSPF process 100 cannot start.

No necesariamente la IP usada participa en OSPF. El uso de loobpacks lo realiza por estabilidad.Antes de ver el proceso de seleccion de DR/BDR se puede observar como va pasando por todos losestados.

2006#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

13.0.0.1 1 INIT/DROTHER 00:00:32 172.17.4.3 FastEthernet0/0



13.0.0.1 1 2WAY/DROTHER 00:00:37 172.17.4.3 FastEthernet0/0


13.0.0.1 1 EXSTART/BDR 00:00:34 172.17.4.3 FastEthernet0/0


13.0.0.1 1 FULL/BDR 00:00:39 172.17.4.3 FastEthernet0/0

Ver vecinos en cada router y los roles DR/BDR.

2003-R#show ip ospf neighbor


14.0.0.1 1 FULL/DROTHER 00:00:36 172.17.4.4 FastEthernet0/0

16.0.0.1 1 FULL/DR 00:00:38 172.17.4.6 FastEthernet0/0










13/114


Ver que en este caso, 2003-R le gano el rol de BDR a 2004-R donde no debera, esto se debe a que laeleccion se produjo antes que 2004-R entrara a competir. Ver tablas de enrutamiento y las LS DBs:

2003-R#show ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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 not set

16.0.0.0/32 is subnetted, 1 subnets

O IA 16.0.0.1 [110/2] via 172.17.4.6, 00:01:46, FastEthernet0/0


C 172.17.4.0 is directly connected, FastEthernet0/0


C 13.0.0.0 is directly connected, Loopback0



2003-R#show ip ospf database

OSPF Router with ID (13.0.0.1) (Process ID 100)

Router Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# Checksum Link count

13.0.0.1 13.0.0.1 1361 0x80000004 0x00F194 1

14.0.0.1 14.0.0.1 151 0x80000008 0x00E19D 1

16.0.0.1 16.0.0.1 1366 0x80000002 0x00DDA1 1

Net Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# Checksum

172.17.4.6 16.0.0.1 151 0x80000004 0x000A22

Summary Net Link States (Area 0.0.0.0)


13.0.0.1 13.0.0.1 1357 0x80000002 0x0062BC

14.0.0.1 14.0.0.1 151 0x80000003 0x004AD1

16.0.0.1 16.0.0.1 93 0x80000002 0x0020F8

Router Link States (Area 0.0.0.3)

Link ID ADV Router Age Seq# Checksum Link count

13.0.0.1 13.0.0.1 1357 0x80000002 0x0032D3 1


14/114


Summary Net Link States (Area 0.0.0.3)


14.0.0.1 13.0.0.1 137 0x80000001 0x0061BC

16.0.0.1 13.0.0.1 1354 0x80000001 0x0047D4

172.17.4.0 13.0.0.1 1358 0x80000005 0x005216

Se ven Router Links aprendidos por los Exchange iniciales, se ven Network Links enviados porel DR, y se ven Summary Links debido a que cada router participante tiene las interfaces loopback enareas independientes. Notar que las LS DBs son por areas a las que pertenece el router.En las capturas captures/dr-bdr/*.pcap se observa la eleccion de DR y BDR. Se ve como arrancan

con los DR y BDR vacos en los Hello, como luego se logra el consenso entre 2003-R y 2006-R. Luegocuando entra 2004-R arranca vaco pero a continuacion aprende el DR y BDR y los toma. Tambien seobserva como arrancan sin vecinos y como se van agregando en los Hello hasta que todos se ven entre si.Otras capturas para observar este proceso en la misma configuraci on son:captures/ospf-dr-election.pcap y captures/ospf-dr-election-2.pcap .

2003-R#debug ip packet

IP packet debugging is on

IP: s=172.17.4.4 (FastEthernet0/0), d=224.0.0.5, len 72, rcvd 0


IP: s=172.17.4.3 (local), d=224.0.0.5 (FastEthernet0/0), len 72,sending broad/multi cast



IP: s=172.17.4.3 (local), d=224.0.0.5 (FastEthernet0/0), len 72,

sending broad/multicast





3.2.3. Ver Mensajes OSPF

Producir un cambio y ver los Updates y la utilizacion de las direcciones de multicast:captures/updates/*.pcap , en particular en captures/updates/01-ospf-update-2003.pcap .

2003#debug ip packet


...




sending broad/multicastIP: s=172.17.4.6 (FastEthernet0/0), d=224.0.0.5, len 72, rcvd 0





15/114


2004(config)#

...


ip address 40.0.0.1 255.0.0.0

!

router ospf 100


network 14.0.0.0 0.0.0.255 area 0.0.0.4

network 40.0.0.0 0.0.0.255 area 0

network 172.17.4.0 0.0.0.255 area 0

!

...

En el primer datagrama IP va el Update desde el router que detecta el cambio hacia todos los routersdesignados (All-OSPF-DRs) y en el segundo va la actualizacion desde el desgindo (DR) a todos los routersOSPF. Ver que el primero usa la direccion de multicast 224.0.0.6 y el resto la 224.0.0.5.



Luego continua con la confirmacion de la actualizacion recibida, pero esta es dirigida a todos los

routers.









Ver los cambios producidos en la tabla de ruteo (RIB).

2003#show ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

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 not set




C 172.17.4.0 is directly connected, FastEthernet0/0


16/114



O 40.0.0.1 [110/2] via 172.17.4.4, 00:03:39, FastEthernet0/0


C 13.0.0.0 is directly connected, Loopback0



Otro cambio se puede ver al sacarse una red. Ver que esta va todos los routers designados:captures/updates/02-ospf-update2-200*.pcap .

2004-R(config)#interface loopback 1

2004-R(config-if)#shutdown

2003-R#








IP: s=172.17.4.6 (FastEthernet0/0), d=224.0.0.5, len 84, rcvd 0IP: s=172.17.4.3 (local), d=224.0.0.5 (FastEthernet0/0), len 72,






Tambien se puede ver el efecto, pero quitando la ruta desde un router que no tiene rol de designado:captures/updates/03-ospf-update-200*.pcap .

2004(config)#interface loopback 0

2004(config-if)#shutdown

3.2.4. Re-eleccion de DR y BDR

Cambiar la Prioridad para que cambie el DR. Para que se vuelva a ejecutar la elecci on se deberestartear el proceso OSPF en todos los routers.





2004-R(config-if)#ip ospf priority ?

Priority

2004-R(config)#interface FastEthernet 0/0


17/114


2004-R(config-if)#ip ospf priority 255

2003-R#clear ip ospf process

Reset ALL OSPF processes? [no]: yes





2004-R#

...

%OSPF-5-ADJCHG: Process 100, Nbr 16.0.0.1 on FastEthernet0/0 from INIT to DOWN,

Neighbor Down: Interface down or detached

%OSPF-5-ADJCHG: Process 100, Nbr 13.0.0.1 on FastEthernet0/0 from INIT to DOWN,

Neighbor Down: Interface down or detached





Ver que Ethernet toma automaticamente el tipo de red Broadcast sin necesidad de configurarsemanualmente sobre la interfaz.

2004-R# show ip ospf interface FastEthernet 0/0

FastEthernet0/0 is up, line protocol is up

Internet Address 172.17.4.4/24, Area 0.0.0.0

Process ID 100, Router ID 14.0.0.1, Network Type BROADCAST, Cost: 1

Transmit Delay is 1 sec, State DR, Priority 255

Designated Router (ID) 14.0.0.1, Interface address 172.17.4.4

Backup Designated router (ID) 13.0.0.1, Interface address 172.17.4.3

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:00

Index 1/2, flood queue length 0

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

Last flood scan length is 1, maximum is 14

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

Neighbor Count is 2, Adjacent neighbor count is 2

Adjacent with neighbor 16.0.0.1

Adjacent with neighbor 13.0.0.1 (Backup Designated Router)

Suppress hello for 0 neighbor(s)

Es importante notar que en este ejemplo, como son 3 router siempre se establecieron adyacencias entretodos. Si hay mas de 3 router en la misma red broadcast siempre entre los routers que no son designados(ni principal, ni backup) no habra ninguna relacion de adyacencia. Por ejemplo se si se agrega un routeral ejemplo anterior, el 2005.

Router 2005


18/114



...

!


ip address 172.17.4.5 255.255.255.0

duplex auto

speed auto

...

!


ip address 15.0.0.1 255.255.255.0

!

router ospf 100


network 15.0.0.0 0.0.0.255 area 0.0.0.5

network 172.17.4.0 0.0.0.255 area 0.0.0.0

!

end

Se ve que el router agregado, 2005, no establece adyacencia con 2003, ya que ambos no son nidesignados ni de backup. La vecindad queda en estado 2WAY.

















Neighbor ID Pri State Dead Time Address Interface15.0.0.1 1 FULL/DROTHER 00:00:30 172.17.4.5 FastEthernet0/0




19/114


3.3. OSPF sobre ATM-DXI, NBMA

Se simula un canal ATM sobre lneas seriales conectados segun la figura 2.

Figura 2: Topologa utilizada para la practica de OSPF NBMA.

Solo se trabaja sobre 2003-R y 2004-R.

3.3.1. Configuraciones y NBMA con Broadcast

El primer ejemplo que se muestra es aprovechando la capacidad de poder enviar broadcast a nivelde enlace. Notar el comando ip ospf network broadcast en cada interfaz. Hay que indicarselo ex-plcitamente no como en ethernet que no es necesario. Sino toma como tipo NBMA. Notar tambienexplcitamente el comando propio de nivel de enlace al cual se le configura soporte para broadcast:dxi map ip broadcast.

Router 2003

2003-R#show running-config interface Serial 0/1

Building configuration...

Current configuration : 221 bytes

!

interface Serial0/1

ip address 172.16.4.2 255.255.255.0

encapsulation atm-dxi

ip ospf network broadcast

load-interval 30

no keepalive

dxi pvc 3 15 snap

dxi map ip 172.16.4.1 2 15 broadcast

end


router ospf 100


network 13.0.0.0 0.0.0.255 area 0


20/114


network 172.16.0.0 0.0.255.255 area 0

!

2003-R#show ip ospf interface Serial 0/1

Serial0/1 is up, line protocol is up

Internet Address 172.16.4.2/24, Area 0


Transmit Delay is 1 sec, State BDR, Priority 1



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

Hello due in 00:00:09


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




Adjacent with neighbor 14.0.0.1 (Designated Router)




14.0.0.1 1 FULL/DR 00:00:38 172.16.4.1 Serial0/1

15.0.0.1 1 FULL/ - 00:00:37 172.16.1.2 Serial0/0

Router 2004




!

interface Serial0/1

ip address 172.16.4.1 255.255.255.0encapsulation atm-dxi


no keepalive

clockrate 128000

dxi pvc 2 15 snap


end


router ospf 100

log-adjacency-changesnetwork 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!



21/114











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








13.0.0.1 1 FULL/BDR 00:00:38 172.16.4.2 Serial0/1

16.0.0.1 1 FULL/ - 00:00:36 172.16.3.1 Serial0/0

Para el broadcast sobre estos canales se basa en la siguiente propiedad descripta en: [CDXI] 1

...ATM Access over a Serial Interface Example: In the following example, serial interface 0 is configured forATM-DXI with MUX encapsulation. Because MUX encapsulation is used, only one protocol is carried onthe PVC. This protocol is explicitly identified by a dxi map command, which also identifies the protocoladdress of the remote node. This PVC can carry IP broadcast traffic...

interface serial 0

ip address 172.21.178.48


dxi pvc 10 10 mux


subsubsectionNBMA sin Broadcast, ATM-DXIEn este caso se utiliza el mismo nivel de enlace pero se utiliza el tipo de red default para ATM-DXI:

NBMA. Ver que 2004-R queda como DR y 2003-R como BDR. Ver que se configura explcitamente elcomando neighbor . en la seccion de ruteo de OSPF indicando cual es el vecino, porqueen este entorno de NON-BROADCAST no lo encontrara sino. Notar el comando ip ospf networknon-broadcast en cada interfaz, aunque no es necesario, como ya se mencion o es el default.

Router 2003




!

interface Serial0/1

ip address 172.16.4.2 255.255.255.0


1(Nota: El ejemplo de la referencia mencionada es diferente a las configuraciones que se usan en el ejemplo.


22/114


no keepalive

ip ospf network non-broadcast

load-interval 30

dxi pvc 2 15 snap

dxi map ip 172.16.4.1 2 15

end


router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

neighbor 172.16.4.1 priority 1

!




Process ID 100, Router ID 13.0.0.1, Network Type NON_BROADCAST, Cost: 781







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








14.0.0.1 1 FULL/DR 00:01:49 172.16.4.1 Serial0/1

15.0.0.1 1 FULL/ - 00:00:37 172.16.1.2 Serial0/0

Router 2004




!

interface Serial0/1ip address 172.16.4.1 255.255.255.0


ip ospf network non-broadcast

no keepalive

clockrate 128000


23/114


dxi pvc 2 15 snap

dxi map ip 172.16.4.2 2 15

end

!


router ospf 100


network 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0


!



13.0.0.1 1 FULL/BDR 00:01:32 172.16.4.2 Serial0/1

16.0.0.1 1 FULL/ - 00:00:34 172.16.3.1 Serial0/0

Notar el tipo de red NON-BROADCAST en las muestras anteriores.

3.3.2. Point-to-Point sobre Multi-acceso, ATM-DXI

Notar el comando ip ospf network point-to-point en cada interfaz de cada router y ver que noexiste DR no BDR.

Router 2003




!

interface Serial0/1

ip address 172.16.4.2 255.255.255.0


ip ospf network point-to-point

load-interval 30

no keepalive

dxi pvc 2 15 snap


end


router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!



24/114



14.0.0.1 1 FULL/ - 00:00:37 172.16.4.1 Serial0/1

15.0.0.1 1 FULL/ - 00:00:37 172.16.1.2 Serial0/0

Router 2004




!

interface Serial0/1

ip address 172.16.4.1 255.255.255.0encapsulation atm-dxi

ip ospf network point-to-point

no keepalive

clockrate 128000

dxi pvc 2 15 snap


end


router ospf 100

log-adjacency-changesnetwork 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!



13.0.0.1 1 FULL/ - 00:00:38 172.16.4.2 Serial0/1

16.0.0.1 1 FULL/ - 00:00:38 172.16.3.1 Serial0/0

Notar el tipo de Red Punto a Punto.




Process ID 100, Router ID 14.0.0.1, Network Type POINT_TO_POINT, Cost: 781

Transmit Delay is 1 sec, State POINT_TO_POINT,




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







25/114


3.3.3. Point-to-Multipoint sobre Multi-acceso, ATM-DXI

Este tipo de red es tratada como varias puntos a puntos tal como se describe en [RFC-2328] o en[COSPFn1]. Transcribiendo de esta ultima:... Point-to-mutipoint: treats non-broadcast network as a collection of point-to-point links by config-uring the ip ospf network point-to-multipoint command. There are no DR and BDR elected whenthe NBMA network is configured as Point-to-Multipoint as shown in the outputs, since it is treated as acollection of point-to-point links...No se muestra el ejemplo, en este caso se corre: ip ospf network point-to-multipoint en cada interfazpero funciona de forma similar que OSPF en P2P.

3.4. OSPF sobre Frame-Relay, NBMA

Se conectan los routers Back2Back en toploga similar a la de la figura 2. Se transcribe desde[COSPFn5]....OSPF treats multipoint Frame Relay interfaces as NON BROADCAST by default. This requires thatneighbors be explicitly configured. There are various methods for handling OSPF over Frame Relay. Theone that is implemented depends upon whether the network is fully meshed. For more information, referto the following documents: When you configure OSPF to run over a broadcast-capable or non-broadcast,multi-access network, all devices must be able to communicate directly with (at a minimum) the desig-nated router. The broadcast and NBMA model relies on the Frame Relay cloud being fully meshed. If apermanent virtual circuit (PVC) goes down, the cloud is no longer fully meshed and OSPF fails to workcorrectly. In a Frame Relay environment, if Layer 2 is unstable, as in our example, we do not recommend

an OSPF broadcast network-type. Use OSPF point-to-multipoint instead...

3.4.1. Configuraciones y NBMA con Broadcast, FR

Es necesario el tipo de red OSPF. Para que utilice el broadcast con el comando ip ospf networkbroadcast, sino no establece la adyacencia. Ademas es indispensable indicar el el DLCI de frame-relayque enva el broadcast, de la misma forma que se hizo con ATM-DXI, sino no funciona. Se transcribe: ...In this configuration, the network type is changed to broadcast with the ip ospf network broadcastcommand. Now, the NBMA network is viewed as a broadcast multi-access network where DR and BDRelection takes place. The frame-relay mapcommands are also set to forward broadcast addresses.

Router 2003

2003-R#show running-config interface Serial 0/1Building configuration...


!

interface Serial0/1

ip address 172.16.4.2 255.255.255.0

encapsulation frame-relay


load-interval 30

no keepalive

frame-relay map ip 172.16.4.1 101 broadcastframe-relay interface-dlci 101

end




26/114










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







router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!



14.0.0.1 1 FULL/DR 00:00:35 172.16.4.1 Serial0/1

Router 2004




!

interface Serial0/1ip address 172.16.4.1 255.255.255.0



no keepalive

clockrate 128000

frame-relay map ip 172.16.4.2 101 broadcast

frame-relay interface-dlci 101

end


Serial0/1 is up, line protocol is upInternet Address 172.16.4.1/24, Area 0






27/114





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







router ospf 100


network 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!



13.0.0.1 1 FULL/BDR 00:00:39 172.16.4.2 Serial0/1

Obteniendo el mismo efecto, tambien se podra haber definido una sub-interfaz de tipo Multipointcon capacidad de broadcast, de la siguiente forma:




!

interface Serial0/1

no ip address


load-interval 30no keepalive

end

2003-R#show running-config interface Serial 0/1.2



!

interface Serial0/1.2 multipoint

ip address 172.16.4.2 255.255.255.0

ip ospf network broadcastframe-relay map ip 172.16.4.1 101 broadcast


end



28/114




!

interface Serial0/1

no ip address


no keepalive

clockrate 128000

end




!


ip address 172.16.4.1 255.255.255.0




end

2003-R#show ip ospf interface Serial 0/1.2

Serial0/1.2 is up, line protocol is up






Flush timer for old DR LSA due in 00:02:01




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






3.4.2. NBMA sin Broadcast, Frame-Relay

Se debe configurar explicitamente el neighbor dentro del comando router. NO es necesario el tipode OSPF network. Igual que en el ejemplo anterior de ATM-DXI tampoco con ip ospf network non-

broadcast. Notar el tipo de red NON BROADCAST en el show....In this configuration, the network is non-broadcast, which does not allow neighbors to be discoveredautomatically. The neighbor command is used to manually configure OSPF neighbors. However, thiscommand is necessary only with Cisco IOS software versions earlier than 10.0. As an alternate solution,issue the ip ospf network broadcastcommand to change the default network type. ...


29/114


Router 2003




!

interface Serial0/1

ip address 172.16.4.2 255.255.255.0


load-interval 30

no keepalive

frame-relay map ip 172.16.4.1 101frame-relay interface-dlci 101

! ### ip ospf network non-broadcast

end




end

2003-R#show running-config | begin ospf 100router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0


!




Process ID 100, Router ID 13.0.0.1, Network Type NON_BROADCAST, Cost: 781Transmit Delay is 1 sec, State BDR, Priority 1



Flush timer for old DR LSA due in 00:02:01




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



Neighbor Count is 1, Adjacent neighbor count is 1Adjacent with neighbor 14.0.0.1 (Designated Router)




30/114



14.0.0.1 1 FULL/DR 00:01:37 172.16.4.1 Serial0/1

Router 2004




!

interface Serial0/1

ip address 172.16.4.1 255.255.255.0


no keepalive

clockrate 128000

frame-relay map ip 172.16.4.2 101


! ### ip ospf network non-broadcast

end


router ospf 100


network 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0


!











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








13.0.0.1 1 FULL/BDR 00:01:34 172.16.4.2 Serial0/1

Tambien se podra haber definido una sub-interfaz de tipo Multipoint sin soporte de broadcastcomo:


31/114


Router 2003




!

interface Serial0/1

no ip address


load-interval 30

no keepalive

end




!


ip address 172.16.4.2 255.255.255.0



! ### ip ospf network non-broadcastend

Similar para 2004.

3.4.3. Point-to-Point sobre Multi-acceso, Frame-Relay

Si se utilizan sub-interfaces de tipo Point-to-point en lugar de Multipoint. NO es necesario con-figurar ningun parametro extra con ip ospf network point-to-point ya por default utiliza el tipodebido al tipo de las sub-interfaces (point-to-point). Notar el tipo de red POINT TO POINT en el show.

Router 2003

2003-R#show running-config interface Serial 0/1Building configuration...


!

interface Serial0/1

no ip address


load-interval 30

no keepalive

end




!


32/114


interface Serial0/1.1 point-to-point

ip address 172.16.4.2 255.255.255.0


! ### ip ospf network point-to-point

end


router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!


%OSPF: OSPF not enabled on Serial0/1









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








14.0.0.1 1 FULL/ - 00:00:34 172.16.4.1 Serial0/1.1

Router 2004




!

interface Serial0/1

no ip address

encapsulation frame-relayno keepalive

clockrate 128000

end



33/114




!

interface Serial0/1.1 point-to-point

ip address 172.16.4.1 255.255.255.0


! ### ip ospf network point-to-point

end

2004-R#show interfaces Serial 0/1


Hardware is PowerQUICC Serial

MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation FRAME-RELAY, loopback not set

Keepalive not set

FR SVC disabled, LAPF state down

Broadcast queue 0/64, broadcasts sent/dropped 58/0, interface broadcasts 51

Last input 00:00:04, output 00:00:03, output hang never

Last clearing of "show interface" counters 00:06:44

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/1/32 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 96 kilobits/sec

...


router ospf 100


network 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!









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







34/114




13.0.0.1 1 FULL/ - 00:00:31 172.16.4.2 Serial0/1.1

3.4.4. Point-to-Multipoint sobre Multi-acceso, Frame-Relay

En esta configuracion se cambia el tipo de red con ip ospf network point-to-multipoint. La redfunciona como una coleccion de redes punto a punto, los vecinos son descubiertos de forma autom atica yno se elige DR ni BDR. Notar el tipo de red POINT TO MULTIPOINT en el show.

Router 2003




!

interface Serial0/1

no ip address


load-interval 30

no keepalive

end




!


ip address 172.16.4.2 255.255.255.0

ip ospf network point-to-multipoint


frame-relay interface-dlci 101end




Process ID 100, Router ID 13.0.0.1, Network Type POINT_TO_MULTIPOINT, Cost: 781

Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,




Next 0x0(0)/0x0(0)Last flood scan length is 1, maximum is 1






35/114




14.0.0.1 1 FULL/ - 00:01:39 172.16.4.1 Serial0/1.2


router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

!

Router 2004




!

interface Serial0/1

no ip address


no keepaliveclockrate 128000

end








Index 2/2, flood queue length 0Next 0x0(0)/0x0(0)








13.0.0.1 1 FULL/ - 00:01:44 172.16.4.2 Serial0/1.2


router ospf 100


network 14.0.0.0 0.0.0.255 area 0


36/114


network 172.16.0.0 0.0.255.255 area 0

!

3.4.5. Point-to-Multipoint, NO Broadcast, Frame-Relay

Routers 2003 y 2004

Es necesario configurar el neighbor.

Se usa el comando ip ospf network point-to-multipoint non-broadcast.




!


ip address 172.16.4.2 255.255.255.0

ip ospf network point-to-multipoint non-broadcast



end

2003-R#show running-config | begin router ospf

router ospf 100log-adjacency-changes

network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

neighbor 172.16.4.1

!




!interface Serial0/1.2 multipoint

ip address 172.16.4.1 255.255.255.0

ip ospf network point-to-multipoint non-broadcast



end



14.0.0.1 1 FULL/ - 00:01:41 172.16.4.1 Serial0/1.22003-R#sh





37/114







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






2004-R#show running-config | begin router ospf

router ospf 100


network 14.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

neighbor 172.16.4.2

!



13.0.0.1 1 FULL/ - 00:01:36 172.16.4.2 Serial0/1.2









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






3.4.6. NO Broadcast (Frame-Relay), Point-to-Point (HDLC)

A continuacion se muestran ejemplos de capturas con NON-Broadcast sobre Frame-Relay y conPoint-to-Point sobre HDLC, pero con routers 3600. Las capturas son:

captures/non-bcast-p2p/ospf-non-bcast.pcap .

captures/non-bcast-p2p/ospf-p2p.pcap .

2003#show version


IOS (tm) 3600 Software (C3620-I-M), Version 12.0(3)T2, RELEASE SOFTWARE (fc1)


38/114



Compiled Thu 08-Apr-99 16:24 by dschwart

Image text-base: 0x600088F0, data-base: 0x60702000

ROM: ROMMON Emulation Microcode

ROM: 3600 Software (C3620-I-M), Version 12.0(3)T2, RELEASE SOFTWARE (fc1)

2003 uptime is 1 minute

System restarted by unknown reload cause - suspect boot_data[BOOT_COUNT] 0x0,

BOOT_COUNT 0, BOOTDATA 19

System image file is "tftp://255.255.255.255/unknown"

cisco 3620 (R4700) processor (revision 0xFF) with 61440K/4096K bytes of memory.

Processor board ID 00000000

R4700 CPU at 80Mhz, Implementation 33, Rev 1.2

Bridging software.

X.25 software, Version 3.0.0.

4 Serial network interface(s)

DRAM configuration is 64 bits wide with parity enabled.

125K bytes of non-volatile configuration memory.

8192K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

Configurar OSPF:

2003(config)#

router ospf 100


network 13.0.0.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 0

Ver el tipo de red:

2003#show ip ospf interface Serial 0/1

Serial0/1 is up, line protocol is upInternet Address 172.16.4.2/24, Area 0


Transmit Delay is 1 sec, State WAITING, Priority 1

No designated router on this network

No backup designated router on this network



Wait time before Designated router selection 00:00:43


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

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



Ver que no establece adyacencia:


39/114



Configurar explcitamente el vecino:

2003(config-router)#neighbor 172.16.4.1

%OSPF-5-ADJCHG: Process 100, Nbr 0.0.0.0 on Serial0/1 from DOWN to ATTEMPT, Start

%OSPF-5-ADJCHG: Process 100, Nbr 0.0.0.0 on Serial0/1 from ATTEMPT to ATTEMPT

Ahora si:

2003#show ip ospf neighborNeighbor ID Pri State Dead Time Address Interface

N/A 0 ATTEMPT/DROTHER 00:01:46 172.16.4.1 Serial0/1

%OSPF-5-ADJCHG: Process 100, Nbr 14.0.0.1 on Serial0/1 from ATTEMPT to INIT,

Received Hello

%OSPF-5-ADJCHG: Process 100, Nbr 14.0.0.1 on Serial0/1 from INIT to 2WAY,

2-Way Received

%OSPF-5-ADJCHG: Process 100, Nbr 14.0.0.1 on Serial0/1 from 2WAY to EXSTART,

AdjOK?

%OSPF-5-ADJCHG: Process 100, Nbr 14.0.0.1 on Serial0/1 from EXSTART to EXCHANGE,

Negotiation Done%OSPF-5-ADJCHG: Process 100, Nbr 14.0.0.1 on Serial0/1 from EXCHANGE to LOADING,

Exchange Done

%OSPF-5-ADJCHG: Process 100, Nbr 14.0.0.1 on Serial0/1 from LOADING to FULL,

Loading Done



14.0.0.1 1 FULL/DR 00:01:48 172.16.4.1 Serial0/1



13.0.0.1 1 FULL/BDR 00:00:16 172.16.4.2 Serial0/1

Ver que los mensajes son Unicast:



IP: s=172.16.4.2 (local), d=172.16.4.1 (Serial0/1), len 68, sending

IP: s=172.16.4.1 (Serial0/1), d=172.16.4.2, len 68, rcvd 0IP: s=172.16.4.2 (local), d=172.16.4.1 (Serial0/1), len 68, sending

Observar el ejemplo como red Point-to-Point sobre HDLC:


40/114


2003(config)#interface Serial 0/1

2003(config-if)#encapsulation hdlc

2004(config)#interface Serial 0/1

2004(config-if)#encapsulation hdlc



IP: s=172.16.4.2 (local), d=224.0.0.5 (Serial0/1), len 68, sending broad/multicast

IP: s=172.16.4.1 (Serial0/1), d=224.0.0.5, len 68, rcvd 0

IP: s=172.16.4.2 (local), d=224.0.0.5 (Serial0/1), len 68, sending broad/multicast


IP: s=172.16.4.2 (local), d=224.0.0.5 (Serial0/1), len 68,



2003#show ip ospf interface Serial 0/1








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








14.0.0.1 1 FULL/ - 00:00:34 172.16.4.1 Serial0/1


41/114


4. OSPF Multiple Area

Referencias [COSPFC], [COSPFD], [COSPFE], y [COSPFF]. Las division en areas de OSPF estapensada para limitar el alance del flooding y reducir la necesidad de recursos:

Limitar Flooding.

Limitar la vista de la DBD topologica.

Reducir el tamano de la DBD y as el uso de memoria.

Reducir el consumo de CPU ante reconfiguraciones.

Tipos de Areas:

Areas Normales.

Areas Stubs.

Areas NSSA (NO So Stubby Area).

Areas Totalmente Stubs (No estandar).

Areas NSSA Totally Stubs (No estandar).

4.1. Normal Area

network area

La comunicacion con las otras areas es a traves de ABRs (Area Border Routers). Pueden ser areasde transito (backbone, area 0) o estandares. El area de backbone es una sola y es a traves de la cualse comunican el resto de las areas. Puede trabajar tanto con LSAs externos como internos. Un areaestandar puede incorporan rutas externas e internas (inter, intra). Generan externas, internas (inter -sololos ABR-, intra).

4.2. Stub Area

network area

area stub

No incorporan redes externas. Si internas (inter-area e intra-area). Se basan en default routes paraalcanzar rutas Externas. Son estandar. Estas filtran los LSA de tipo 5, E1 y E2. La ruta default la debegenerar de el ABR del area. No deberan tener mas de una salida. Todos los routers del area debenacordar estar en area Stub.

4.3. NSSA (No So Stubby Area)

network area

area nssa

Son como las Stubs pero pueden generar rutas Externas desde el area. Si aceptan rutas internas (inter-area e intra-area) y generan externas. Las externas son rutas generadas a partir de otros protocolos deenrutamiento y que se distribuyen va OSPF. No aceptan externas de otras areas (LSA 5). No son unaextension propietaria. Dentro del area las externas se manejan como LSA 7 y los ABR del area cuando lapasan a la 0 las transforman en LSAs 5. Todos los routers del area deben acordar estar en area NSSA.


42/114


4.4. Totally Stub Area

network area

area stub no-summary

No se incorporan rutas externas ni interas (inter-area), solo intra-area, toda la salida se realiza pordefault routes. Si pueden generar LSAs internos al area (intra-area) e incorporar los mismos. Son unaextension propietaria de cisco. Solo el ABR puede saber que es Totalmente Stub, el resto la puedeconsiderar solo Stub. Esto es necesario para generar las rutas defaults y no incorporar informacion deotras areas. Transcribiendo de las referencias:... Ospf totally stub area (cisco propietary, filter type 5 LSA, type 3 IA O, and type 4 IA O from populatingstub areas router routing table) Totally stubby area, which is a Cisco proprietary feature...

4.5. NSSA Totally Stub Area

network area

area nssa no-summary

Son con las NSSA pero ademas no permiten el ingreso de redes inter-area. O son como una TotallyStub que puede generar rutas externas. Se generan como Type 7 y se exportan a las otras areas comoType 5, de la misma forma que las NSSA. Ni LSA 3 ni 4 son permitidos. Solo es necesario configuraren los NSSA ABRs. Las Totally Stubs son tambien propias de cisco (propietarias).

4.6. Topologa Basica

Figura 3: Topologa utilizada para la practica de OSPF Multi-area.


43/114


4.7. Configuracion OSPF Multi-Area

En esta practica ademas de los 2600 habituales se agrega un Cisco Catalyst 3550 (Multilayer).

L3-2008#show version


IOS (tm) C3550 Software (C3550-I5Q3L2-M), Version 12.1(22)EA1, RELEASE SOFTWARE (fc1)


Compiled Mon 12-Jul-04 09:21 by madison

Image text-base: 0x00003000, data-base: 0x0083AEF4

ROM: Bootstrap program is C3550 boot loader

L3-2008 uptime is 1 week, 5 days, 8 hours, 41 minutes

System returned to ROM by power-on

System image file is "flash:c3550-i5q3l2-mz.121-22.EA1.bin"

cisco WS-C3550-24 (PowerPC) processor (revision J0) with 65526K/8192K bytes of memory.

Processor board ID CAT0734X03P

Last reset from warm-reset

Bridging software.

Running Layer2/3 Switching Image

Ethernet-controller 1 has 12 Fast Ethernet/IEEE 802.3 interfaces

Ethernet-controller 2 has 12 Fast Ethernet/IEEE 802.3 interfaces

Ethernet-controller 3 has 1 Gigabit Ethernet/IEEE 802.3 interface

Ethernet-controller 4 has 1 Gigabit Ethernet/IEEE 802.3 interface

24 FastEthernet/IEEE 802.3 interface(s)

2 Gigabit Ethernet/IEEE 802.3 interface(s)

The password-recovery mechanism is enabled.384K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address: 00:0D:BD:DC:8D:80

Motherboard assembly number: 73-5700-10

Power supply part number: 34-0966-03

Motherboard serial number: CAT073401Q0

Power supply serial number: DTH07320SQM

Model revision number: J0

Motherboard revision number: A0

Model number: WS-C3550-24-EMI

System serial number: CAT0734X03P

Configuration register is 0x10F

4.7.1. Configuraciones de los Routers

2008-R

!


44/114


hostname L3-2008

!

ip routing

!

!

interface Loopback0

ip address 18.0.0.1 255.255.255.252

!

!


switchport access vlan 2

switchport mode dynamic desirable

no shutdown

!




no shutdown

!

interface FastEthernet 0/13



no shutdown

!

interface Vlan1

ip address 172.16.5.2 255.255.255.0

no shutdown

!

!

interface Vlan2

ip address 180.0.0.1 255.255.255.0

no shutdown

!

router ospf 100


default-information originate

network 0.0.0.0 255.255.255.255 area 0.0.0.0

!

ip route 0.0.0.0 0.0.0.0 180.0.0.2

!

end

!

L3-2008#show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID Local Intrfce Holdtme Capability Platform Port ID

L2-2002 Fas 0/2 150 S I WS-C2950T-Fas 0/1

2004-R Fas 0/7 140 R 2620XM Fas 0/0

(Solo para dar link)


45/114


2006-R Fas 0/13 123 R 2620XM Fas 0/0

!

Costos de las interfaces:

F a0 / 13

ospf pract

Documents