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A single level of confusion for some CCNA and CCNP candidates is the variation involving configuring a static default route and using the Cisco routing command ip default-network.

At first look, they seem to do the very same thing. The two configure a location to which packets ought to be routed if there is no a lot more particular route in the routing table.

The important big difference among these two alternatives is that configuring a static default route only defines a default route for the router you are configuring it on, while ip default-network will propagate the route by means of its routing protocol.

Why don't we look at the routing tables of a hub-and-spoke network making use of the ip default-network command. R1 is the hub and R2 and R3 are the spokes. They are immediately linked by way of the network 172.twelve.123. /24, and just about every has a loopback with a 32-little bit mask that are numbered in accordance to the router amount (1.one.1.1, and so on.) RIP is managing on all about three routers and the loopbacks are marketed.

R1 has one more serial interface with the IP deal with 10.1.1.1 /24, and this network has been flagged as a default network with the command ip default-network ten... . It is not currently being marketed by RIP.

The routing protocol will then promote this route. With RIP, the default network is marketed as ... . (With IGRP, it appears as the network number, but is marked as an IGRP External route. ) This route has been specified a applicant default route on R1, as we see with the asterisk up coming to the ten... /24 network (code table taken off for brevity)

R1show ip route

Gateway of final resort is not set

1.../32 is subnetted, one subnets
C one.1.1.one is immediately connected, Loopback0
R 2.../8 120/one through 172.twelve.123.two, 000011, Serial0
R 3.../8 120/1 by way of 172.twelve.123.three, 000011, Serial0
172.twelve../sixteen is variably subnetted, two subnets, 2 masks
C 172.12.21./30 is directly related, BRI0
Do 172.12.123./24 is straight linked, Serial0
* ten.../24 is subnetted, one subnets
Do 10.1.one. binary options reviews is right related, Serial1

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

R2show ip route
Gateway of final resort is 172.twelve.123.1 to network ...

R one.../8 one hundred twenty/one by way of 172.twelve.123.1, 000000, Serial0.213
2.../32 is subnetted, 1 subnets
Do two.two.2.2 is specifically linked, Loopback0
R 3.../eight a hundred and twenty/2 by means of 172.twelve.123.1, 000000, Serial0.213
172.12../sixteen is variably subnetted, 2 subnets, 2 masks
Do 172.12.21./thirty is immediately linked, BRI0
Do 172.twelve.123./24 is immediately connected, Serial0.213
R* .../ one hundred twenty/one via 172.twelve.123.one, 000000, Serial0.213

R3show ip route
Gateway of very last resort is 172.twelve.123.one to network ...

R one.../8 a hundred and twenty/1 via 172.12.123.1, 000027, Serial0.31
R two.../8 one hundred twenty/2 through 172.12.123.1, 000028, Serial0.31
three.../32 is subnetted, one subnets
Do three.three.3.3 is immediately connected, Loopback0
172.12../24 is subnetted, one subnets
C 172.twelve.123. is straight related, Serial0.31
R* .../ 120/1 by means of 172.twelve.123.one, 000028, Serial0.31

And the default route will work, because we can ping ten.1.one.1 from both equally R2 and R3. Due to the fact they have no other match in their routing tables, they use the default route.

R2ping 10.one.1.1

Variety escape sequence to abort.
Sending five, 100-byte ICMP Echos to 10.one.one.one, timeout is 2 seconds
!!!!!
Accomplishment charge is one hundred p.c (five/5), spherical-excursion min/avg/max 68/68/68 ms

R3ping 10.1.1.one

Variety escape sequence to abort.
Sending five, 100-byte ICMP Echos to ten.1.1.one, timeout is 2 seconds
!!!!!
Achievement charge is 100 percent (5/five), spherical-journey min/avg/max 68/68/68 ms

When determining no matter if to use a default static route or a default network, keep in intellect 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 regional router to have the default route, a static IP route is the way to go.
 

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