IPv6 Flashcards
How many bits are in an IPv6 address?
128
IPv6 address are 128 bits represented in ___ groups of ___ hex characters
8 groups of 4 hex characters
T/F: IPv6 addresses don’t use slash (CIDR) notation for denoting prefix length
F
IPv6 only uses slash notation for prefix length, no more subnet masks
T/F: IPv6 addresses do not use a subnet mask (dotted decimal) whatsoever
T
IPv6 uses slash notation only
T/F: Leading zeroes can be removed from each group of 4 hex digits in an IPv6 address
T
Ex: …:001B:… can be shortened to :1B:
T/F: Any quartet of all 0’s can be shortened with ::
F
This can only be done once per address.
For example ->
2001:0DB8::80:34BD is valid, while
2001::BA::34BD is not valid
Why can’t we shorten consecutive quartets of IPv6 addresses more than once in an IPv6 address?
We wouldn’t know where in the address the bits in between the consecutive quartets lies
What is the typical prefix length for an IPv6 block requested by an enterprise from an ISP
/48
What is the typical subnet prefix length for IPv6
/64
Therefore, an enterprise has 16 bits to use to make subnets with
T/F: Link-Local addresses must be manually added to a router interface
F
They are automatically added when you configure a router interface with an IPv6 address
T/F: Link-Local addresses are automatically added to a router interface when it is assigned an IPv6 address
T
What is the command to enable IPv6 routing on a Cisco router
ipv6 unicast-routing
What is the command to assign an IPv6 address to an interface on a Cisco router
ipv6 address [ipv6]
What is the command to view IPv6 interface configurations
sh ipv6 interface brief
What is EUI-64
Extended Unique Identifier (technically Modified EUI in IPv6)
A method of converting a 48 bit MAC address into a 64-bit interface identifier, which can then become the host portion of a /64 IPv6 address
What are the steps to convert a MAC address to a /64 IPv6 host portion
1) Divide the MAC address in half
1234 5678 90AB -> 1234 56 | 78 90AB
2) Insert FFFE in the middle
1234 56FF FE78 90AB
3) Invert the 7th bit
1034 56FF FE78 90AB
4) Add the result to a network prefix to make a complete IPv6 address
Why do we invert the 7th bit of a MAC in EUI-64
MACs can be either universally assigned or locally assigned. The 7th bit of a mac address determines this. In the context of IPv6 addresses, the meaning of the bit is inverted from a MAC, so we change it to match IPv6/EUI-64
T/F: Global Unicast addresses are globally unique and must be assigned by an internet authority
T
What is the IPv6 global unicast address range
All addresses which aren’t reserved for other purposes
What is a unique local address
A private address for use within a LAN, cannot be used over the internet
T/F: Unique local addresses must be registered with an internet authority
F
What is the unique local address block
FC00:: /7
However, the 8th bit has to be set to 1, so the first two digits must be FD
FD00:: /7
What is the FC00:: /7 block designated for
Unique local addresses. However, since the 8th bit must be set, it will really always be FD00:: /7
T/F: The 40-bit ‘global ID’ for a unique local address should be incrementally assigned, so that if two companies merge networks, they won’t have conflicts
F
The 40-bit ‘global ID’ after the FD should be randomly generated to prevent merge conflicts, since its extremely unlikely that they will have overlapping addresses
What is a link-local address?
An address than is used for communication within a single link (subnet)
T/F: You can use the command ipv6 enable on an interface to enable IPv6 on an interface, and both a link local and unique local address will be generated for it
F
Only a link local address will be generated for the interface
T/F: You can use the command ipv6 enable on an interface to enable IPv6 on an interface, and only a link local address will be generated and assigned to the interface
T
What is the link local address block
FE8:: /10
What are some common uses for link local addresses?
- Routing protocol peerings (OSPFv3)
- Next-hop addresses for static routes
- Neighbor Discovery Protocol (NDP, IPv6’s replacement for ARP)
What are the types of IPv6 address?
1) Global Unicast
2) Link Local
3) Multicast
4) Anycast
T/F: Multicast addresses are used for one-to-many communication. AKA from one source to multiple destinations that have joined a specific multicast group
T
T/F: IPv6 doesn’t use broadcast addresses
T
T/F: For a one-to-all message, IPv6 sends it to a specific multicast address, not a strictly broadcast address
T
What is the IPv6 address for all nodes communication
FF02::1
What is the FF02::1 address reserved for?
All nodes communication
List the IPv6 multicast address scopes
1) Interface Local
2) Link Local
3) Site Local (beyond CCNA)
4) Organization Local (beyond CCNA)
5) Global (beyond CCNA)
T/F: Anycast messaging is a new feature of IPv6 and has no IPv4 direct equivalent
T
Anycast messages are defined as ____ to ______
one to one of many
Anycast messages have _____ possible destinations, and traffic is sent to _________
multiple, only one
T/F: Anycast messages fall within the FE8:: /10 address block
F
Anycast messages have no specific range. Regular unicast addresses may be used
T/F: Anycast messages do not have an assigned block of addresses that must be used
T
What is the command to assign an anycast address to an interface on Cisco devices?
ipv6 address [ip address] anycast
What does the IP address :: mean
The unspecified address
Equivalent to 0.0.0.0, generally used when a device doesn’t know its IPv6 address yet. IPv6 default routes are also configured to ::/0
What is the IPv6 loopback address
::1
What is the IPv6 address ::1
Loopback
T/F: Per RFC 5952, leading 0’s in a hex quartet MUST be shortened
T
T/F: Per RFC 5952, the use of the :: abbreviation MUST be used to its maximum capability
T
However, a :: cannot replace a single field of all 0’s. Instead, use a single 0
2001:db8:0:1:1:1:1:1 is correct, but
2001:db8::1:1:1:1:1 is incorrect
T/F: Per RFC 5952, you may use a :: to replace a single quartet of all 0’s
F
Per RFC 5952, you must replace this with a single 0
T/F: Per RFC 5952, if there are more than 1 groups of simultaneous all 0 quartets, you must use :: to replace the smallest
F
You have to replace the largest of the all zero quartets. IE:
2001:0:0:1:0:0:0:1 -> 2001:0:0:1::1
If they are equal in size, choose the first sequence
2001:0:0:1:0:0:1:1 -> 2001::1:0:0:1:1
T/F: Per RFC 5952, regardless of the size of the all zero quartet groupings, you replace the first with ::
F
The largest should be replaced with ::, however if they are of equal size, then the first should be replaced
EX:
2001:0:0:1:0:0:0:1 -> 2001:0:0:1::1
If they are equal in size, choose the first sequence
2001:0:0:1:0:0:1:1 -> 2001::1:0:0:1:1
T/F: Per RFC 5952, hex characters in IPv6 addresses MUST be represented in lower case
T
All hex chars should be lower case
The IPv6 header is ____ bits long
288
T/F: The IPv6 header is a fixed length
T
T/F: The IPv6 header is variable length
F
The IPv6 header is fixed length
The IPv6 header is ____ bytes long
40
The version field of the IPv6 header is ___ bits long
4
The version field of the IPv6 header is always set to:
6 (0100)
The traffic class field of the IPv6 header is ___ bits long
8
The traffic class field of the IPv6 header is used for:
QoS and traffic prioritization
The flow label field of the IPv6 header is ___ bits long
20
The flow label field of the IPv6 header is used for:
Identifying specific traffic flows (comms between a specific source and a destination)
The payload length field of the IPv6 header is ___ bits long
16
The payload length field of the IPv6 header is used for:
Indicating the length of the L4 segment encapsulated by the packet
This does not include the length of the IPv6 header
T/F: The length of the IPv6 header is included in the payload length
F
Since the header is a fixed size it isn’t included in the payload length field
The next header field of the IPv6 header is ___ bits long
8
The next header field of the IPv6 header is used for:
Indicating the type of the header of the encapsulated L4 segment, for example, TCP or UDP
The hop limit field of the IPv6 header is ___ bits long
8
The source and destination fields of the IPv6 header is ___ bits long
128 bits each
An IPv6 solicited node multicast address is calculated from a fixed prefix plus
The last 6 hex digits of the unicast address that the solicited node address is being generated form
What is the fixed prefix for calculating a solicited node multicast address
ff02::1:ff
ARP is replaced by ___ in IPv6
NDP
NDP uses the _____ protocol to learn the MAC address of other hosts
ICMPv6
What are the two message types of NDP
1) Neighbor Solicitation (NS) = ICMPv6 Type 135
2) Neighbor Advertisement (NA) = ICMPv6 Type 136
NDP Neighbor Solicitation messages use ___
ICMPv6 Type 135
NDP Neighbor Advertisement messages use ___
ICMPv6 Type 136
In an NDP NS message, the destination MAC address is:
A solicited node multicast MAC address
In an NDP NS message, the destination IPv6 address is:
The destination’s solicited-node multicast address
Explain the big difference between an ARP request message and an NDP NS message
An ARP request message is broadcast, and an NDP NS message is multicast. Therefore, the NDP NS message is more efficient.
The IPv6 equivalent of an ARP table is called a:
Neighbor table
What is the command to view an IPv6 neighbor table on a Cisco device
sh ipv6 neighbor
T/F: NDP also provides a facility for automatically discovering routers on the LAN
T
What are the two message types used by NDP’s router discovery functionality
1) Router solicitation (RS)
2) Router advertisement (RA)
NDP RS messages use:
ICMPv6 type 133
NDP RA messages use:
ICMPv6 type 134
NDP RS messages are sent to multicast address:
FF02::2 (all routers)
NDP RA messages are sent to multicast address:
FF02::1 (all nodes)
T/F: NDP RA messages are sent in response to RS messages, but are also periodically sent by a router without having first received an RA message
T
Much like gratuitous ARP
T/F: NDP RA messages are only sent in response to RS messages
F
RA messages are sent periodically, even if an RS message isn’t received
SLAAC stands for:
Stateless Address Auto-configuration
What is the purpose of SLAAC
Automatically determining a unique and routable IPv6 address for a host
T/F: Both SLAAC and DHCPv6 can be used simultaneously
T
T/F: SLAAC and DHCPv6 are not able to be used simultaneously
F
SLAAC and DHCPv6 can be used together
Name a benefit of SLAAC use
Minimal configuration is required on hosts, minimal config on a router (if it exists), and no additional servers
Describe how SLAAC generates an IPv6 address
1) Host sends RS/RA messages to learn the IPv6 prefix of the local link (ie 2001:db8::/64)
2) Host generates an interface identifier that uniquely identifies an interface on a subnet, either by using EUI-64 or random generation, depending on the device/maker
3) An IPv6 address is formed by combining the two
3a) If there are no routers on the net, SLAAC can only generate a link-local address
DAD stands for:
Duplicate Address Detection
T/F: Anytime an IPv6 enabled interface initializes, or an IPv6 address is configured on an interface, it performs DAD
T
T/F: DAD is only performed when an IPv6 device is manually configured
F
DAD is performed anytime an IPv6 enabled interface initializes, or an IPv6 address is configured on an interface
DAD uses these two message types:
NS and NA
Describe how DAD works
1) Host sends an NS to its own IPv6 address
2) If no reply is received, the device knows the address is unique
2a) If a reply is received, then the device knows another host on the net is using the address
T/F: IPv6 routing works the same as IPv4 routing
T
T/F: IPv6 routing works differently than IPv4 routing
F
T/F: IPv6 routes are stored in the same routing table as IPv4 addresses
F
T/F: IPv6 addresses are maintained in a different routing table than IPv6 addresses
T
T/F: Routes for IPv6 link local addresses are added to the routing table
F
Link-local address routes are not added to the routing table
T/F: Routes for IPv6 link local addresses aren’t added to the routing table
T
What is the command for adding an IPv6 static route to a Cisco router
ipv6 route destination/prefix-length {next-hop | exit-interface [next-hop]} [ad]
T/F: In IPv6, you can’t use directly attached static routes if the interface is an Ethernet interface
T
T/F: In IPv6, you can only use a recursive or fully specified static route
T
T/F: To use a link-local address for a next hop, you have to enter a fully configured static route
T
