Default Routing and configuration

Default Routing - Default Routing is something called gateway of last resort, when a specific route to a particular network does not exist, a router will drop all the packets destined to that specific network. Router forward packets using a default route when there is no specific routes that match a packet’s destination IP address in the routing table. The default route can be identified by all zeros in both the network and subnet mask (0.0.0.0 0.0.0.0). It is the least specific route possible. Default route are also use to connect ISP site or head site.

Routing protocols like RIPv2, EIGRP, and OSPF can advertise default routes, each router chooses the best default route to list as that router’s gateway of last resort.

In short:

 “Default route is used by IP to forward any packet with destination not found in the routing table.”

Methods of  advertising default routes in RIP:

·         

      

 Learning default route in RIPv2- Configuration of default route in RIPv2-

Topology:

·         Configure the interface as per the diagram

·         Configure static routing route from ISP to R2

·         Configure a default route on R2 (Head Office) to provide connectivity to internet routs(15.0.0.1-15.0.2.1)

R1#show ip interface brief

Interface                    IP-Address          OK? Method     Status                Protocol

FastEthernet0/0        192.168.1.10    YES manual            up                    up

Serial3/0                         10.0.0.1        YES manual              up                    up

R2#show ip interface brief

Interface                      IP-Address      OK? Method           Status                Protocol

FastEthernet0/0        192.168.1.20    YES manual              up                    up

Serial3/0                         10.1.1.2        YES manual               up                    up

Serial3/1                         12.1.1.1        YES manual               up                    up

Serial3/2                         11.1.1.1        YES manual               up                    up

R3#show ip interface brief

Interface                      IP-Address           OK? Method Status                Protocol

FastEthernet0/0        192.168.1.30      YES manual up                           up

Serial3/1                     12.1.1.2               YES manual up                           up

R4#show ip interface brief

Interface              IP-Address      OK? Method           Status                Protocol

FastEthernet0/0        192.168.1.40    YES manual        up                    up

Serial3/2                         11.1.1.2        YES manual          up                    up

Loopback0                    15.0.0.1        YES manual            up                    up

Loopback1                   15.0.1.1        YES manual            up                    up

Loopback 2                   15.0.2.1        YES manual           up                    up

[Configure RIPv2]

R1(config)#router rip

R1(config-router)#version 2

R1(config-router)#network 10.0.0.0

R1(config-router)#network 192.168.1.0

R1(config-router)#no auto-summary

R2(config)#router rip

R2(config-router)#version 2

R2(config-router)#network 10.0.0.0

R2(config-router)#network 192.168.1.0

R2(config-router)#network 12.0.0.0

R1(config-router)#no auto-summary

R2(config)#ip route 0.0.0.0 0.0.0.0 11.1.1.2

R4(config)#ip route 10.0.0.0 255.0.0.0 11.1.1.1

R4(config)#ip route 12.0.0.0 255.0.0.0 11.1.1.1

R4(config)#ip route 192.168.1.0 255.255.255.0 11.1.1.1

(Advertise default route in RIPv2)

R2(config)#router rip

R2(config-router)#default-information originate

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 10.1.1.2 to network 0.0.0.0

R*    0.0.0.0/0 [120/1] via 10.1.1.2, 00:00:15, Serial3/0

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

C        10.0.0.0/8 is directly connected, Serial3/0

L        10.0.0.1/32 is directly connected, Serial3/0

R     12.0.0.0/8 [120/1] via 10.1.1.2, 00:00:15, Serial3/0

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C        192.168.1.0/24 is directly connected, FastEthernet0/0

L        192.168.1.10/32 is directly connected, FastEthernet0/0

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 12.1.1.1 to network 0.0.0.0

R*    0.0.0.0/0 [120/1] via 12.1.1.1, 00:00:08, Serial3/1

R     10.0.0.0/8 [120/1] via 12.1.1.1, 00:00:08, Serial3/1

      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C        12.0.0.0/8 is directly connected, Serial3/1

L        12.1.1.2/32 is directly connected, Serial3/1

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C        192.168.1.0/24 is directly connected, FastEthernet0/0

L        192.168.1.30/32 is directly connected, FastEthernet0/0

R1#ping 15.0.0.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 15.0.0.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 44/58/68 ms

R1#ping 15.0.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 15.0.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 64/84/136 ms

R3#traceroute 15.0.0.1

Type escape sequence to abort.

Tracing the route to 15.0.0.1

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

  1 12.1.1.1 72 msec 80 msec 64 msec

  2 11.1.1.2 128 msec 140 msec 136 msec

(Configuring another method of redistribution to advertise default route in RIPv2)

R2(config)#router rip

R2(config-router)#version 2

R2(config-router)#no default-information originate

R2(config-router)#redistribute static

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 12.1.1.1 to network 0.0.0.0

R*    0.0.0.0/0 [120/1] via 12.1.1.1, 00:00:29, Serial3/1

R     10.0.0.0/8 [120/1] via 12.1.1.1, 00:00:29, Serial3/1

      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C        12.0.0.0/8 is directly connected, Serial3/1

L        12.1.1.2/32 is directly connected, Serial3/1

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C        192.168.1.0/24 is directly connected, FastEthernet0/0

L        192.168.1.30/32 is directly connected, FastEthernet0/0

R3#ping 15.0.0.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 15.0.0.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 36/56/136 ms

R1#ping 15.0.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 15.0.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 40/67/112 ms

[In the next section we will configure default EIGRP methods and OSPF methods]