A network engineer must implement an IPv6 configuration on the vlan 2000 interface to create a routable locally-unique unicast address that is blocked from being advertised to the internet. Which configuration must the engineer apply?
A.
interface vlan 2000 ipv6 address ff00:0000:aaaa::1234:2343/64
B.
interface vlan 2000 ipv6 address fd00::1234:2343/64
C.
interface vlan 2000 ipv6 address fe80:0000:aaaa::1234:2343/64
D.
interface vlan 2000 ipv6 address fc00:0000:aaaa::a15d:1234:2343:8aca/64
fc00 : 0000 : aaaa :: a15d : 1234 : 2343 : 8aca
1st 2nd 3rd 5th 6th 7th 8th
I separated in this way to show you that it´is missing the 4th hextet. Guess where it must be?
D is correct man.
I would disagree that D is correct. Looking at the address, if, :: is considered has been shortened already, therefore, bringing it back to its normal addressing it would have 9 octets instead of 8.
The RFC doesn't matter if the CCNA 200-301 Official Cert Guide says otherwise, and it does. It says a double colon can only be used for "two ore more quartets of all 0s". No other sources matter when this is the authority for the CCNA exam. See CCNA 200-301 Official Cert Guide, Volume 1, Chapter 22, page 531 for that exact quote, towards the bottom of that page.
Yes it can be used to abbreviate a single set of zeroes, but the standards do recommend shortening the left most set of zeroes if two sets of equal sizes are available within the address. So the one in option D does not satisfy this recommendation.
Option B uses fd00::/64, which is within the ULA range. This address prefix ensures that the network is not supposed to be routed outside of the local network, thus inherently blocking advertisement to the internet.
Option D uses fc00::/8, which is also part of the ULA space but includes the full interface ID, making it valid for a local address. However, the address in option B (fd00::/64) is more commonly used and directly aligns with the standard for ULA configuration for privacy and ease of use.
In IPv6, “unique local” addresses (ULAs) are the correct choice for an internal-only, routable address that is not advertised on the global Internet. The ULA space is fc00::/7, which typically shows up as addresses beginning with fc or fd. Among the options given:
• ff00::… is a multicast address (not a unicast host address).
• fe80::… is a link-local address (only valid on the local link and not routable across subnets).
• fc00::… or fd00::… belong to the Unique Local Address space (fc00::/7). These are routable within a site but not globally advertised.
Because the question explicitly wants a “locally-unique unicast address that is blocked from being advertised to the internet,” the best-fit ULA is typically in the fd00::/8 range (option B), which is why
interface vlan 2000
ipv6 address fd00::1234:2343/64
is the correct solution.
B is correct. While D falls within the block, that subnet is not currently used. Keep in mind that weird thing about Unique Local addresses: The address block FC00::/7 is actually split into two equally sized halves, fc00::/8 and fd00::/8.fc00::/8, is currently not defined, so while it falls under the Unique Local prefix, it's actually not in use. Currently, only fd00::/8 is used and considered legitimate to assign to an interface.
Y'all forgetting a key characteristic about ipv6 unique local address which is super relavant here: the 40 bits following "fc" or "fd" MUST be RANDOMLY GENERATED so B is incorrect
D is correct and yes :: can be used to abbreviate a single set of "0000"
I just tested on lab. It seems that the address fc00 : 0000 : aaaa :: a15d : 1234 : 2343 : 8aca is legitimate and the command "do show int" shows the interface use the ip without any error . I vote for D.
I just run answer B to the same interface and command "show ipv6 interface brief" shows the two address. I changed my mind. I will choose answer B because B seems to be a more formal answer according to the discussion.
Options A, C, and D do not provide a ULA address. Option D includes an address from the Unique Local Address (ULA) range but also includes a global routing prefix (fc00::/7), which is not typically used for ULAs and may lead to confusion or potential routing issues. Therefore, option B is the correct choice for creating a routable locally-unique unicast address that is not advertised to the Internet.
To create a locally-unique unicast IPv6 address that is not routable on the internet, the engineer should use a Unique Local Address (ULA), which falls within the fc00::/7 prefix. Therefore, option D is the correct choice:
D. interface vlan 2000 ipv6 address fc00:0000:aaaa::a15d:1234:2343:8aca/64
Diretly from CISCO book:
NOTE Just to be completely exact, IANA actually reserves prefix FC00::/7, and not
FD00::/8, for these addresses. FC00::/7 includes all addresses that begin with hex FC and
FD. However, an RFC (4193) requires the eighth bit of these addresses to be set to 1, which
means that in practice today, the unique local addresses all begin with their first two digits
as FD
Agree and upvoting. Per RFC 4193 Section 3.1, "...[zero] my be defined in the future," and Section 3.2.2; Line Item 6 regarding setting the "L" bit to 1, hence the FD. Though the prefix starts w/ FC, application is done using FD.
D is correct, the '::' == 0000. that makes it 16 bytes which is 128bits
furthermore, it can only be unique-local because it has to be routable within the network(like private ipv4 addresses).
one more thing, fc00::/7 is the only one that would be correct as well, cuz thats the start of a unique-local address
The answer to this question is D
Here's why:
ff00::: These addresses are reserved for multicast purposes and cannot be used for unicast routing. So, option A is incorrect.
fd00::: These addresses are unique local addresses (ULA) but are globally routable. So, option B is incorrect.
fe80::: These addresses are link-local addresses and cannot be routed outside the local link. So, option C is incorrect.
fc00::: These addresses are unique local addresses (ULA) with a globally unique interface identifier (GUID). They are not advertised to the internet by default due to the privacy extension mechanism, while still being routable within the local network. This matches the requirements of the scenario.
Option 'b' is correct.
Wow - a lot of confusion here!
Options 'b' and 'd' are technically correct - it has nothing to do with IPv6 address length.
It's just a matter of which one is "more correct"?
ULA is defined as FC00::/7, *however* FC00::/8 is not defined, only FD00::/8 is.
For this reason, the answer is 'b'.
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