Chapter 23 - IPv6 Addressing and Subnetting Flashcards
What are Global Unicast IPv6 addresses?
- Work like public IPv4 addresses in that;
- An organization registers for an IPv6 address block. This is assigned as a global routing prefix
- Only the organization registered against this block of IPv6 addresses can use them
- Originally made of of any address that begins with a 2 or a 3. Now any address that is not reserved for other purposes.
What are Unique Local IPv6 addresses?
- Works like private IPv4 addresses in that;
- Organizations don’t have to register to use these addresses
- Can’t be routed over the internet
- Multiple organizations can use the same addresses. They don’t have to be globally unique but it is best practice to make them this way.
- Any address beginning with FD or FC.
What is a Global Routing Prefix?
- A reserved block of IPv6 addresses that only the registered organization can use
- Can be subnetted into smaller networks (as with IPv4 blocks)
- All addresses in a particular block will begin with the same global routing prefix
What prefixes are reserved for which types of IPV6 addresses?
- Global Unicast - Originally anything beginning with 2 or 3. Now it is anything that has not been reserved for another purpose.
- Unique Local - Anything beginning with FD or FC
- Multicast - Anything beginning with FF
- Link Local - Anything beginning with FE80
What three parts are Global Unicast addresses comprised of? What extra part is added for Unique Local?
- Similar to IPv4, IPv6 addresses have a:
- Global Routing Prefix (similar to the IPv4 network part which cannot be changed for addresses in the same subnet)
- (For Unique Local only) Global ID
- Subnet (The same as the IPv4 subnet part. Bits can be borrowed from the host)
- Interface ID (The same as the IPv4 Host part)
What is another name for the Subnet ID?
Subnet Router Anycast Address
Like an IPv4 network address, this should not be applied to any host.
What is the name of the IPv6 specific built-in dynamic IP address assignment method?
SLAAC - Stateless Address Autoconfiguration
What rules must Unique Local addresses follow?
- Use FD or FC as the first two hex digits
- Chooses a unique global ID that is;
- Global ID is whatever is leftover after adding the Interface ID length, FD length (8 bits), and Subnet ID length together. For
example if the Interface ID is 64 bits and the Subnet ID is 16 bits, the Global ID will be 40 bits.
True or False. It is not necessary to make your Unique Local address Global ID unique.
True and False. It is not necessary because Unique Local addresses are not publicly routable, however, it is good practice to try to make them unique in case, for example, your company merged with another.
What is a Link Local address?
- Automatically generated on any IPv6 enabled interface
- Any address that starts with FE80::/10, however, the standard states that you should only ever see FE8. All host bits should be 0s.
- Dynamically Generated using EUI-64 per interface
- Only used for communication within a broadcast domain (link).
- Traffic with a dst of a link local address will not be forwarded by routers
- Used in OSPFv3, NDP, and Static routes with an outgoing interface
For example if PC1 pinged PC2s Global Unicast address, it could reach it by using the link local address of multiple routers as next hops. PC1 could also ping R1s link local address (as they are on the same link) but could not ping R2s link local address since R1 wouldn’t forward it.
What are common uses for Link Local addresses?
- Routing Protocol Peerings - OSPFv3 uses link local addresses to form neighbor adjacencies and send LSAs
- Next hop addresses for static routes
- NDP in general. If a Neighbor has not been discovered yet then the dst will be solicited node multicast but the src will be the sender’s link local. The responder will then use the original sender’s link local as dst and its own link local as src.
