Exam 300-410 topic 1 question 72 discussion

Correct answer is A. Please note that A1, A2, B1 and B2 are Customer routers, therefore they have no idea of VRF.

I was skeptical if A was correct, but after I labbed, indeed is A. CE routers do not need to configure VRF, however, if VRF was configured, it works as well.

A is correct

A Explanation A1 and A2 routers do not know they belong to VRF A. The two interfaces of ISP (which are connected to A1 & A2) should be configured like this (we only show the configure of one interface): ISP router: interface g0/0 description ISP->To_CustomerA ip vrf forwarding A ip address 172.31.100.2 255.255.255.0 router ospf 100 vrf A network 172.31.200.2 0.0.0.255 area 0

Its A: A1 interface fa0/0 description To->ISP ip add 172.31.100.1 255.255.255.0 no shut ! router ospf 100 net 172.31.100.1 0.0.0.255 area 0 A2 interface fa0/0 description To->ISP ip add 172.31.200.1 255.255.255.0 no shut ! router ospf 100 net 172.31.200.1 0.0.0.255 area 0

Answer "A", because we need to perform the configuration on the customer edges, and not on the ISP.

Answer B and C are very similar but answer B has wrong IP address on router A2, answer C has the correct configuration for VRF lite to work.

As the stament says VRF is fully configured on ISP, customerr routers just have to do is the necesary routing to communicate each other.

A is correct, the ISP configures the VRF-lite not the customer

A is the correct answer. Firstly, VRF is not configured on the client side that is already completed on the ISP router. Secondly, in the available answers none mentioned the creation of the VRF.

Hello. The question clearly mentions that "The ISP router is FULLY CONFIGURED ... " , not the customer routers... Therefore, the correct answer is A because it doesn't contain any VRF info ( Customers are unaware of the VRF concept ) , and it has the correct IPs. Other than that, all the "vrf-related" answers are incorrect, because they don't mention anywhere the VRF-related creation commands .

The question stated the they need too make use of the VRF lite Feature what implies that VRF Forwarding needs too be used. There is also a type error in the answers See : https://itexamanswers.net/question/refer-to-the-exhibit-the-isp-router-is-fully-configured-for-customer-a-and-customer-b-using-the-vrf-lite-feature-what-is-the-minimum-configuration-required-for-customer-a-to-communicate-between-rout

The question stated the they need too make use of the VRF lite Feature what implies that VRF Forwarding needs too be used. There is also a type error in the answers See : https://itexamanswers.net/question/refer-to-the-exhibit-the-isp-router-is-fully-configured-for-customer-a-and-customer-b-using-the-vrf-lite-feature-what-is-the-minimum-configuration-required-for-customer-a-to-communicate-between-rout

It’s clearly that A is correct answer, after assign vrf you setup ospf for routing in the vrf.

A1 and A2 are CE, no VRFs there.

i agree with A, since A1 and A2 are CE they dont need vrf config, its only necesary in Pe, in this case in ISP router

This is the only config which would work A1 interface fa0/0 description To->ISP ip vrf forwarding A ip add 172.31.100.1 255.255.255.0 no shut ! router ospf 100 net 172.31.100.1 0.0.0.255 area 0 A2 interface fa0/0 description To->ISP ip vrf forwarding A ip add 172.31.200.1 255.255.255.0 no shut ! router ospf 100 net 172.31.200.1 0.0.0.255 area 0