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1 stage of confusion for some CCNA and CCNP candidates is the big difference involving configuring a static default route and using the Cisco routing command ip default-network.

At first glance, they appear to do the similar factor. Each configure a destination to which packets need to be routed if there is no far more certain route in the routing table.

The main difference among these two choices is that configuring a static default route only defines a default route for the router you might be configuring it on, whilst ip default-network will propagate the route by means of its routing protocol.

Let us examine the routing tables of a hub-and-spoke network employing the ip default-network command. R1 is the hub and R2 and R3 are the spokes. They are directly linked through the network 172.twelve.123. /24, and just about every has a loopback with a 32-bit mask that are numbered according to the router amount (one.one.1.one, etc.) RIP is operating on all 3 routers and the loopbacks are advertised.

R1 has a different serial interface with the IP deal with ten.one.one.1 /24, and this network has been flagged as a default network with the command ip default-network ten... . It is not becoming marketed by RIP.

The routing protocol will then promote this route. With RIP, the default network is marketed as ... . (With IGRP, it seems as the network quantity, but is marked as an IGRP Exterior route. ) This route has been specified a candidate default route on R1, as we see with the asterisk following to the 10... /24 network (code table taken out for brevity)

R1show ip route

Gateway of previous resort is not set

one.../32 is subnetted, one subnets

Do one.one.one.1 is directly related, Loopback0

R two.../eight one hundred twenty/1 by way of 172.twelve.123.two, 000011, Serial0

R 3.../8 a hundred and twenty/1 via 172.12.123.three, 000011, Serial0

172.twelve../sixteen is variably subnetted, 2 subnets, 2 masks

C 172.12.21./30 is immediately linked, BRI0

Do 172.12.123./24 is specifically related, Serial0

* 10.../24 is subnetted, 1 subnets

Do ten.one.one. home options is straight linked, Serial1

On R2 and R3, a default RIP route is now noticed (code tables once more deleted)

R2show ip route

Gateway of previous resort is 172.twelve.123.1 to network ...

R 1.../8 120/1 by means of 172.twelve.123.1, 000000, Serial0.213

two.../32 is subnetted, 1 subnets

C two.2.2.2 is directly related, Loopback0

R 3.../eight one hundred twenty/2 through 172.twelve.123.1, 000000, Serial0.213

172.twelve../16 is variably subnetted, 2 subnets, two masks

Do 172.twelve.21./thirty is right linked, BRI0

Do 172.12.123./24 is directly connected, Serial0.213

R* .../ a hundred and twenty/1 via 172.12.123.one, 000000, Serial0.213

R3show ip route

Gateway of previous resort is 172.12.123.1 to network ...

R one.../eight one hundred twenty/1 by means of 172.twelve.123.1, 000027, Serial0.31

R two.../eight 120/two via 172.twelve.123.one, 000028, Serial0.31

three.../32 is subnetted, one subnets

C three.three.three.three is straight connected, Loopback0

172.twelve../24 is subnetted, one subnets

Do 172.twelve.123. is directly linked, Serial0.31

R* .../ one hundred twenty/one by means of 172.12.123.1, 000028, Serial0.31

And the default route performs, since we can ping ten.1.1.1 from both equally R2 and R3. Because they have no other match in their routing tables, they use the default route.

R2ping 10.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to ten.one.1.one, timeout is two seconds

!!!!!

Accomplishment amount is a hundred percent (five/five), spherical-journey min/avg/max 68/68/68 ms

R3ping 10.1.one.one

Variety escape sequence to abort.

Sending 5, a hundred-byte ICMP Echos to ten.one.1.one, timeout is 2 seconds

!!!!!

Results fee is one hundred % (5/five), spherical-excursion min/avg/max 68/68/68 ms

When deciding no matter if to use a default static route or a default network, preserve in brain that if you want the routing protocol to propagate the default route, the ip default-network command will do that for you. But if you want only the community router to have the default route, a static IP route is the way to go.