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Question 233

A customer requested a GRE tunnel through the provider network between two customer sites using loopback to hide internal networks. Which configuration on

R2 establishes the tunnel with R1?

    Correct Answer: B

    To establish a GRE tunnel through the provider's network between two customer sites using the loopback interface to hide internal networks, it is essential to consider the correct use of IP addresses for the tunnel source and destination. Loopback interfaces typically use private IP addresses, and the 10.10.x.x network addresses in option B are suitable for such a configuration, making them more appropriate for private internal networks. The MTU setting of 1400 helps in managing the tunnel's packet size. Therefore, option B is the correct configuration for establishing the GRE tunnel.

Discussion
ChillingAgain

I think we are missing some info in the question to correctly answer this one. A. R2(config)#interface Tunnel1 R2(config-if)#ip address 172.20.1.2 255.255.255.0 R2(config-if)#ip mtu 1400 R2(config-if)#ip tcp adjust-mss 1360 R2(config-if)#tunnel source 192.168.20.1 R2(config-if)#tunnel destination 192.168.10.1 B. R2(config)#interface Tunnel1 R2(config-if#ip address 172.20.1.2 255.255.255.0 R2(config-if)#ip mtu 1400 R2(config-if)#ip tcp adjust-mss 1360 R2(config-if)#tunnel source 10.10.2.2 R2(config-if)#tunnel destination 10.10.1.1 C. R2(config)#interface Tunnel1 R2(config-if)#ip address 172.20.1.2 255.255.255.0 R2(config-if)#ip mtu 1500 R2(config-if)#ip tcp adjust-mss 1360 R2(config-if)#tunnel source 10.10.2.2 R2(config-if)#tunnel destination 10.10.1.1 D. R2(config)#interface Tunnel1 R2(config-if)#ip address 172.20.1.2 255.255.255.0 R2(config-if)#ip mtu 1500 R2(config-if)#ip tcp adjust-mss 1360 R2(config-if)#tunnel source 192.168.20.1 R2(config-if)#tunnel destination 10.10.1.1

default_routeOption: B

I can´t find a better form to explain my answer other than writing it in my native language, spanish: la pregunta pide establecer un túnel GRE haciendo uso de loopbacks con el fin de ocultar las redes internas (privadas) del cliente.. la respuesta es A o B (por el ip mtu 1400).. yo digo que la respuesta no puede ser A porque establece los túneles con IP's que son clásicas de redes internas/privadas en sitios de clientes y por ende no ocultaría dicha info.. por tanto mi respuesta es B.. source y destination son IP's menos clásicas para redes internas que las IP's de la opción A.

dapardo

pienso igual pero no he encontrado ninguna fuente relevante que respalde esto...igual me voy por la B

XBfoundX

This question is just crap! Who can know what networks is the customer using and the provider using? We can assume that the customer have a small network or is using class C networks and so the provider is using class A networks for the loopbacks. The point is that both A and B can be right it depends on which networks the ISP and the customer are using....

dapardoOption: B

its B, class C is prefered

Mohammad963

I think we cannot answer this Q without exhibit, the only different is with IP address.... please correct me if I'm wrong

[Removed]Option: A

wouldn't option A or B be correct?

inteldarvidOption: B

team for me is B, because, I prefer use Ip class "C" 192.168.1.0/24 for tunnel of gre. I think we are missing some info in the question to correctly answer this one

HungarianDishOption: A

Agree, it's "A" or "B". tunnel source Loopback0 (or the IP) + destination is the IP of the loopback interface on the other end of the tunnel.

DUBC89xOption: A

Agreeded, but the answer has to be A or B "IP MTU 1400"

SeMo0o0o0Option: B

B is correct The addresses 10.10.2.2 and 10.10.1.1 are more commonly used for loopback addresses, rather than class C range.

RickAO76Option: A

A & B setup correctly. https://community.cisco.com/t5/networking-knowledge-base/how-to-configure-a-gre-tunnel/ta-p/3131970 I "guess for this part of the question, " between two customer sites using loopback to hide internal networks", I would lean towards Class C, instead of Class A. But it's just a guess at this point.

RickAO76

revisited " two customer sites" - leaning to Class A now. 10.* - answer B.

bk989Option: B

Google: "Cisco recommends Class C addresses for small organizations with fewer than 256 hosts. For larger organizations, Cisco recommends Class A or Class B addresses. " Since this is for customer sites I choose Class A (the 10.x.x.x)

ZamanROption: A

A or B? A is my answer

inteldarvidOption: A

https://community.cisco.com/t5/networking-knowledge-base/how-to-configure-a-gre-tunnel/ta-p/3131970

inteldarvidOption: A

sorry option A