Cisco Routing: "ip default-network" vs. Default Static Routes
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steven
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#1
03-01-2016, 01:57 PM

1 point of confusion for some CCNA and CCNP candidates is the distinction in between configuring a static default route and utilizing the Cisco routing command ip default-network.

At first glance, they seem to do the exact same factor. Both configure a destination to which packets need to be routed if there is no far more distinct route in the routing table.

The major distinction among these two choices is that configuring a static default route only defines a default route for the router you're configuring it on, although ip default-network will propagate the route by means of its routing protocol.

Let's examine the routing tables of a hub-and-spoke network utilizing the ip default-network command. R1 is the hub and R2 and R3 are the spokes. They are straight connected through the network 172.12.123. /24, and each has a loopback with a 32-bit mask that are numbered according to the router quantity (1.1.1.1, and so on.) RIP is operating on all three routers and the loopbacks are advertised.

R1 has an additional serial interface with the IP address ten.1.1.1 /24, and this network has been flagged as a default network with the command ip default-network 10... In the event you need to be taught more on http://houzz.com/pro/alexghazarian/alex-ghazarian/, there are many on-line databases you might pursue. . It is not getting advertised by RIP.

The routing protocol will then advertise this route. This pictorial https://www.youtube.com/channel/uczbhifq...tpkknx3iq/ web page has uncountable tasteful cautions for how to do it. With RIP, the default network is advertised as ... . (With IGRP, it appears as the network quantity, but is marked as an IGRP External route. ) This route has been designated a candidate default route on R1, as we see with the asterisk subsequent to the 10... /24 network (code table removed for brevity):

R1#show ip route

Gateway of last resort is not set

1.../32 is subnetted, 1 subnets

C 1.1.1.1 is straight connected, Loopback0

R 2.../8 [120/1] via 172.12.123.2, 00:00:11, Serial0

R three.../eight [120/1] through 172.12.123.three, 00:00:11, Serial0

172.12../16 is variably subnetted, two subnets, two masks

C 172.12.21./30 is directly connected, BRI0

C 172.12.123./24 is straight connected, Serial0

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

C ten.1.1. is directly connected, Serial1

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

R2#show ip route

Gateway of last resort is 172.12.123.1 to network ...

R 1.../eight [120/1] via 172.12.123.1, 00:00:00, Serial0.213

2.../32 is subnetted, 1 subnets

C two.2.two.2 is directly connected, Loopback0

R three.../8 [120/two] through 172.12.123.1, 00:00:00, Serial0.213

172.12../16 is variably subnetted, 2 subnets, two masks

C 172.12.21./30 is straight connected, BRI0

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

R* .../ [120/1] through 172.12.123.1, 00:00:00, Serial0.213

R3#show ip route

Gateway of last resort is 172.12.123.1 to network ...

R 1.../eight [120/1] by way of 172.12.123.1, 00:00:27, Serial0.31

R two.../8 [120/two] by way of 172.12.123.1, 00:00:28, Serial0.31

three.../32 is subnetted, 1 subnets

C 3.3.three.three is directly connected, Loopback0

172.12../24 is subnetted, 1 subnets

C 172.12.123. is straight connected, Serial0.31

R* .../ [120/1] by way of 172.12.123.1, 00:00:28, Serial0.31

And the default route functions, considering that we can ping 10.1.1.1 from each R2 and R3. Since they have no other match in their routing tables, they use the default route.

R2#ping 10.1.1.1

Type escape sequence to abort.

Sending five, 100-byte ICMP Echos to ten.1.1.1, timeout is 2 seconds:

!!!!!

Accomplishment price is one hundred % (five/five), round-trip min/avg/max = 68/68/68 ms

R3#ping ten.1.1.1

Type escape sequence to abort.

Sending five, one hundred-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:

!!!!!

Accomplishment rate is one hundred % (five/5), round-trip min/avg/max = 68/68/68 ms

When deciding whether to use a default static route or a default network, keep in thoughts that if you want the routing protocol to propagate the default route, the ip default-network command will do that for you. Dig up additional info on our related portfolio by browsing to http://www.houzz.com/pro/alexghazarian/alex-ghazarian/. To get more information, you can view at: soundcloud.com/alexghazarian/. But if you want only the local router to have the default route, a static IP route is the way to go..
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