IPv6

Question 1

Name the benefits of IPv6

Answer 1

• Larger address space
• Simplified header, easier implementation
• Better Auto-config
• Better flow associativity

Question 2

How are IPv6 addresses formatted?

Answer 2

Leading zeros can be removed
Largest group may be omitted (::)
Port: [2001:db8::1]:80

Question 3

How large are address subnets for IPv6?

Answer 3

First N bits: global routing prefix
Next 64 - N bits: subnet ID
Last 64 bits: Interface ID

Question 4

Name the 4 address scopes and the 4 Uniqueness levels of IPv6 addresses

Answer 4

Unicast: 1-1
Multicast: 1-all
Anycast: 1- 1 (in group)
Broadcast: unused

Global-Unique Address: globally addressable
Local-Unique Address: locally addressable; part of fc00::/7
Link-Local Address: addressable on the link; globally unique. Part of fe80::/10 subnet
Site-Local Address: unused

Question 5

How are Multicast addresses constructed?

Answer 5

First 8 bits are only 1s
Next 4 bits as flag (permanent or transient addr
Next 4 bits as scope
Last 112 bits: GroupID

Question 6

What scopes do exist for IPv6 Multicast addresses?

Answer 6

0000 reserved
0001 Interface local
0010 Link local
1000 Organization local
1110 Global
1111 reserved

Question 7

What IPv6 Multicast addresses are pre-defined?

Answer 7

All nodes MC:
FF01::1 (iface local)
FF02::1 (link local)

All routers MC:
FF01::2 (iface local)
FF02::2 (link local)

Question 8

How does address resolution work in ipv6?

Answer 8

• No ARP but NDP (Neighbour discovery protocol)
• SLAAC (stateless auto configuration)
• Stateful config (router decides if SLAAC should be used)

Question 9

How does SLAAC address generation work?

Answer 9

Fe80::/64 as base
24 bit of iface identifier (first 24 bit of mac) - Invert 2. Bit of first octet (NW byte order - from right!)
Middle 16 bit: ff:fe
Last 24 bit: last 24 bit of MAC address

DAD (duplicate detection)

Question 10

How does SLAAC configuration work?

Answer 10

Generate SLAAC Addr
Hosts join all-nodes mc address
Hosts communicate to routers using all-routers mc address
ICMPv6 router solicitation (from host)
ICMPv6 router advertisement (from all routers) - includes prefixes for site and global

Question 11

How does NDP work?

Answer 11

Neighbor solicitation:

• Ask for MAC address of interface which has the IPv6 addr
• Dst IPv6 addr: ff02:0:0:0:0:1:ff:XX:XXXX.

Question 12

Explain how Router Solicitation and Router Advertisement work

Answer 12

Router Solicitation:
- Sent when iface comes up; Prompt all routers to send a RA

Router Advertisement:

• All-nodes MC addr in fixed interval
• Information: Autoconfig methods (SLAAC, DHCPv6), Prefix info, Route info, MTU on link, Link-Layer address of router)

Question 13

What is the Privacy Extension?

Answer 13

Uses a random 64bit into for host part which is changed regularly

Question 14

What security problem arises with RS/RAs?

Answer 14

Everybody can claim to be a router.

• RA Guard to filter unauthorized RAs
• SEND unter development

Question 15

Explain that possibilities exist to move from IPv4 to IPv6

Answer 15

Dual Stack: All hosts have both protocol until everythink uses IPv4
Tunneling: Encapsulate IPv6 into IPv4
Header translation:
- Stateless IP/ICMP translation
- Defines a class of IPv6 addresses which come from IPv4 addr
- use the ::ffff:0:0:0/96 subnet - ::ffff:0:a.b.c.d
- allows IPv6 only to IPv4 only

Question 16

What is dual-stack lite?

Answer 16

Private IP instead of Public IPv4 & Carrier-Grade NAT
no p2p (gaming, VoIP)

Question 17

How does the 6to4 translation work?

Answer 17

• Local router encapsulates IPv6 into IPv4; transmit to nearest relay
  Source IPv4 addr is embedded in IPv6 addr:
• 6to4 prefix: 2002::/16 & append public IPv4 addr to get 2002:ab:cd::/48
• Address IPv4 packets to 192.88.99.1 (IPv4 Anycast)

Dual stacks on 6to4 relays, 6to4 routers

Question 18

What benefits does the 6to4 translation have?

Answer 18

• Devices behind the gateway can configure an addr inside 2002:ab:cd::/48 subnet
• Gateway encapsulates all IPv6 into IPv4
• All IPv6 pck to 2002:ab:cd::/48 reach the gateway encapsulated in IPv4
• Complete transparency to clients