HOTSPOT
You have three servers named Server1, Server2, and DO that run Windows Server 2012. IPv6 addresses and
configurations are assigned to all of the servers by using DHCPv6.
The IPv6 routing on Server1 is shown in the following table.
You verify that Server2 can ping the IPv6 address of DC1.
You need to ensure that Server1 can ping the IPv6 address of DC1.
What command should you run on Server1? (To answer,select the appropriate options in the answer area.)
Answer: 
Explanation:
Can someone explain the logic behind the above answer? Thanks 😀
New-NetRoute – we can’t modify existing route, we have to add a new one.
Destination prefix and Interface index – There are already two unique local address (FC::/7, equivalent of private network) routes defined (FDDD:…), both of them are for interface 12, and both of them are /128 meaning that only these two hosts are pingable from Server2 at the moment. To ensure Server2 can ping any host in this private network, one has to add a route to it. fddd:eef8:223b:ea3f/64 is the network id (remember, 64 bits!), fddd:eef8:223b:ea3f:a54f:dca7::/32 is equivalent to fddd:eef8::/32, and is not a valid network id.
Next-Hop – just route it to an interface
Thanks, Jay, but did you mean “To ensure Server1 can ping any host in this private network”? The question is asking about Server1 & not 2. Also, can you provide a more thorough explanation? I understand IPv6 addressing, but not so much routing.
Agreed New-NetRoute is the command to add a new route
There is no such route as FC::/7 in the routing table.
Agreed fddd etc is an internal IPv6 Address that is routable internally only.
The other items need more study and verification.
This is how I worked out the answer:
Sherlock Holmes rule of thumb, eliminate the items that do not apply and you will get the answer no matter how unlikely.
1. New-NetRoute adds a new route
2. The IF – Interface Index is typically 12 based on reading this Microsoft article:
https://technet.microsoft.com/en-us/library/hh826150.aspx
The IF is also shown as 12 on Server2 after deducing the IPv6 address in Step 4
3. The next hop is always shown as :: in the routing table.
4. There is a choice of 2 IPv6 addresses in the answer, one has a 64bit mask, the other one has a 32bit mask,
If you try to find a match for the IPv6 address for DC01 in the routing table for Server2 then the only match for FDDD (internally routable) is the one with 64bit mask ending in ea3f::/64
Enable ipv6 on your NIC, then run cmd as Administrator, type “route print”, go to interfaces list, you will see:
1………………………Software Loopback Interface 1
this is software (virtual) device, not hardware NIC
=> 1 ::1/128
1 ff00::/8
not interesting for us
next type “netsh interface ipv6 isatap set state enable”, retype “route print”, compare with previous, you will obtain somthing like this:
9 Microsoft ISATAP Adapter #3
and new string in active routes, like this:
9 fe80::5efe:192.168.1.119/128
thus
=> 14 fe80…..0.221/128
also virtual device – ISATAP Adapter.
(Why not Teredo address? Because there are no any Global addresses in route table)
In system from qustion only one hardware NIC – interface 12
12 fe80::……………./128
Link-local (automatic) address
12 fe80::/64
12 ff00::/8
link-local subnets
=> not interesting
remain two routes fddd………../128
=> Site-Local Addresses (private)
Why two?
Don’t now, but think next
one – temporary from stateless address auto configuration
and another normal ipv6 address
if type “netsh interface ipv6 set privacy state=disable” temporary ipv6 address will be disabled
Site-local addresses have the following structure:
Interface ID 64 bits => subnet /64
Summary:
1)Command – – New-NetRoute – there is no string for Site-local subnet in route table
2)DestinationPrefix – /64 – for Site-local subnet
3)InterfaceIndex – 12
https://technet.microsoft.com/en-us/library/bb726952.aspx