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Doubt about OSPF and longest match

viniciusribas28
Level 1
Level 1

Hi guys, can anyone help me with a problem here? I was having trouble understanding the longest match rule for selecting the best route, I researched about it and finally I understood, but then another doubt came to me, using the OSPF protocol, I configured 3 routers, on R1, R2, R3. R1 : f1/0: 10.0.0.10/16, f0/0: 192.168.1.1/24.R2: f0/0: 192.168.1.2/24, f1/0: 192.168.10.2/24. R3: f0/0: 192.168.10.3/24, f1/0: 10.0.0.15/24. Beauty as expected I could ping to f1/0 of R3(10.0.0.15/24) and could not ping thanks to the longest match rule on f1/0 of R1(10.0.0.10/16) . And there's my doubt, is there any way to ping the f1/0 of R1? Configuring an int loopback with this ip, I know I could ping, after all the propagated network would be /32, but in the game of real life how would it work? despite these range of addresses that I'm using are private, if they were public, how would the service provider prevent ranges from conflicting as in this case? do they only use loopbacks?

 

Sorry for my english, it's not my first language

Screenshot from 2022-05-18 06-39-46.png

1 Accepted Solution

Accepted Solutions

Hello


@viniciusribas28 wrote:

if they were public, how would the service provider prevent ranges from conflicting as in this case? do they only use loopbacks?

Publicly routable or not networks cannot overlap , in this case you would need to "hide" either subnet from each other and one way to do this would be behind Network Address Translation (NAT)


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

View solution in original post

4 Replies 4

In internet there is no private ip only public ip.

And thanks to NAT that hide the private ip behind public ip.

So no conflict at all.

Hello,

 

the tiny screenshot is unreadable unfortunately, post a higher resolution image.

Hello


@viniciusribas28 wrote:

if they were public, how would the service provider prevent ranges from conflicting as in this case? do they only use loopbacks?

Publicly routable or not networks cannot overlap , in this case you would need to "hide" either subnet from each other and one way to do this would be behind Network Address Translation (NAT)


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Thanks Paul, it helped me a lot.

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