Pruebas de redistribución de la ruta por
defecto en OSPF
Fecha: 3 de noviembre del 2014 Clase: #899, módulo 8, CCNA 2 R&S
Escenario
Estudiando sobre OSPF en el aula, conversamos sobre que pasaría si dos routers publican la ruta
por defecto en OSPF: prevalece una sobre otra, o balancea carga ? la respuesta mas lógica es que
balanceara carga entre las dos, ya que coinciden máscaras, AD y el costo, pero en el Packet Tracer
la cosa se comportó diferente, a verificarlo con los equipos entonces…
Pruebas en Packet Tracer
Router_5(config)#ip route 0.0.0.0 0.0.0.0 null0 (creamos la primer ruta por defecto)
Router_5(config)#router ospf 1
Router_5(config-router)#default-information originate (publicamos en OSPF)
Router_5(config-router)#^Z
Router_5#
Router_4#sh ip route (verificamos en el vecino)
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 192.168.72.5 to network 0.0.0.0
C 192.168.72.0/24 is directly connected, FastEthernet0/0
O*E2 0.0.0.0/0 [110/1] via 192.168.72.5, 00:00:57, FastEthernet0/0
Router_4#
Router_4#debug ip routing (para verificar los cambios en la tabla de enrutamiento)
IP routing debugging is on
Router_4#
Router_1#conf t (agregamos la segunda ruta por defecto al escenario)
Router_1(config)#ip route 0.0.0.0 0.0.0.0 null0
Router_1(config)#router ospf 1
Router_1(config-router)#default-information originate
Router_1(config-router)#^Z
Router_1#
Router_4#
RT: del 0.0.0.0 via 192.168.72.5, ospf metric [110/1]
RT: delete network route to 0.0.0.0 (elimina la ruta)
RT: NET-RED 0.0.0.0/0
RT: SET_LAST_RDB for 0.0.0.0/0
NEW rdb: via 192.168.72.1
RT: add 0.0.0.0/0 via
192.168.72.1, ospf metric [110/1] (agrega la ruta)
RT: NET-RED 0.0.0.0/0
Router_4#sh ip route (verificamos
y muestra la última agregada)
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 192.168.72.1 to network 0.0.0.0
C 192.168.72.0/24 is directly connected, FastEthernet0/0
O*E2 0.0.0.0/0 [110/1] via 192.168.72.1, 00:00:14, FastEthernet0/0
Router_4#
Pruebas con equipos reales
Router_5(config)#ip route 0.0.0.0 0.0.0.0 null0 (creamos la primer ruta por defecto)
Router_5(config)#router ospf 1
Router_5(config-router)#default-information originate (publicamos en OSPF)
Router_5(config-router)#^Z
Router_5#
Router_4#sh ip route (verificamos en el vecino)
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 192.168.72.5 to network 0.0.0.0
C 192.168.72.0/24 is directly connected, FastEthernet0/1
O*E2 0.0.0.0/0 [110/1] via 192.168.72.5, 00:02:15, FastEthernet0/1
Router_4#
Router_4#debug ip routing
IP routing debugging is on
Router_4#
Router_1#conf t (agregamos la segunda ruta por defecto al escenario)
Router_1(config)#ip route 0.0.0.0 0.0.0.0 null0
Router_1(config)#router ospf 1
Router_1(config-router)#default-information originate
Router_1(config-router)#^Z
Router_1#
Router_4#
*Nov 3 20:04:27.877: RT: NET-RED 0.0.0.0/0
*Nov 3 20:04:57.949: RT: add 0.0.0.0/0 via 192.168.72.1,
ospf metric [110/1](agrega la ruta)
*Nov 3 20:04:57.949: RT: NET-RED 0.0.0.0/0
*Nov 3 20:04:57.949: RT: NET-RED 0.0.0.0/0
Router_4#
Router_4#sh ip route (verificamos y balancea carga)
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 192.168.72.5 to network 0.0.0.0
C 192.168.72.0/24 is directly connected, FastEthernet0/1
O*E2 0.0.0.0/0 [110/1] via 192.168.72.5, 00:03:16, FastEthernet0/1
[110/1]
via 192.168.72.1, 00:00:13, FastEthernet0/1
Router_4#
Ya que estamos, verificamos que pasaría si Router_5 tiene dos rutas por defecto y las
publica a ambas en el OSPF. Esta prueba se realizó con los equipos y con PT con resultados
similares, el OSPF publica unicamente el gateway para alcanzar la ruta por defecto y no la
cantidad de rutas que posee.
Router_1(config)#no ip route 0.0.0.0 0.0.0.0 null0 (eliminamos la ruta null anterior)
Router_5(config)#no ip route 0.0.0.0 0.0.0.0 null0 (eliminamos la ruta null anterior)
Router_5(config)#int loop 0
Router_5(config-if)#ip add 190.0.0.1 255.255.255.255
Router_5(config-if)#exit
Router_5(config)#int loop 1
Router_5(config-if)#ip add 200.0.0.1 255.255.255.255
Router_5(config-if)#exit
Router_5(config)#ip route 0.0.0.0 0.0.0.0 loop 0
Router_5(config)#ip route 0.0.0.0 0.0.0.0 loop 1
Router_5(config)#^Z
Router_5#
Router_4#debug ip routing (verificamos desde el vecino)
IP routing debugging is on
Router_4#RT: SET_LAST_RDB for 0.0.0.0/0
NEW rdb: via 192.168.72.5
RT: add 0.0.0.0/0 via 192.168.72.5, ospf metric [110/1]
RT: NET-RED 0.0.0.0/0
Router_4#
Router_5#sh ip route (verificamos)
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 0.0.0.0 to network 0.0.0.0
190.0.0.0/32 is subnetted, 1 subnets
C 190.0.0.1 is directly connected, Loopback0
C 192.168.72.0/24 is directly connected, FastEthernet0/0
200.0.0.0/32 is subnetted, 1 subnets
C 200.0.0.1 is directly connected, Loopback1
S* 0.0.0.0/0 is directly
connected, Loopback0
is
directly connected, Loopback1
Router_5#
Router_4#sh ip route (verificamos desde el vecino)
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 192.168.72.5 to network 0.0.0.0
C 192.168.72.0/24 is directly connected, FastEthernet0/0
O*E2 0.0.0.0/0 [110/1] via 192.168.72.5, 00:00:45, FastEthernet0/0
Router_4#
(2014) Reading about OSPF a
rainy Sunday afternoon
Rosario, Argentina