CORRECTION TO PRIOR LECTURES:
RFC Requirements for IPv6 Address Representation
- Leading 0s MUST be removed
- This - 2001 : 0db8 : 0000 : 0001 : 0f2a : 4fff : fea3 : 00b1
- Becomes - 2001 : db8 : 0 : 1 : f2a : 4fff : fea3 : b1
- :: MUST be used to shorten the longest string of all-0 quartets
- If there is only ONE all-0 quartet, don’t use ‘::’
- This - 2001 : 0000 : 0000 : 0000 : 0f2a : 0000 : 0000 : 00b1
- Becomes - 2001 :: f2a : 0 : 0 : b1
- If there are two equal-length choices for the :: , use :: to the shorten the one on the LEFT
- This - 2001 : 0db8 : 0000 : 0000 : 0f2a : 0000 : 0000 : 00b1
- Becomes - 2001 : db8 :: f2a : 0 : 0 : b1
- Hexadecimal characters ‘a’, ‘b’, ‘c’, ‘d’, ‘e’, and ‘f’ MUST be written using lower-case, NOT upper case A B C D E F
IPv6 HEADER
Length is ALWAYS 40 bytes (Fixed Header)
Version (4 bits)
- Indicates version of IP used
- Fixed value of ‘6’ (0b0110) to indicate IPv6
Traffic Class (8 bits)
- Used for QoS (Quality of Service) to indicate high-priority traffic
- Example: IP phone traffic, live video calls, etc.
Flow Label (20 bits)
- Identifies specific traffic “flows” (communication between Source and Destination)
Payload Length (16 bits)
- Indicates the LENGTH of the PAYLOAD (the encapsulation LAYER 4 SEGMENT) in bytes
- The length of the IPv6 header, itself, isn’t included, because it’s ALWAYS 40 bytes
Next Header (8 bits)
- Indicates the TYPE of the ‘next header’ (header of the encapsulated SEGMENT)
- Example: TCP or UDP
- Same function as the IPv4 header’s ‘Protocol’ field
Hop Limit (8 bits)
- Value in this field decrements by 1 every time a ROUTER forwards it. If it reaches ‘0’, the PACKET is discarded (similar to IPv4 TTL field )
Source Address (128 bits)
- Packet’s SOURCE address
Destination Address (128 bits)
- Packet’s DESTINATION address
SOLICITED-NODE MULTICAST ADDRESS
- An IPv6 SOLICITED-NODE Multicast Address is calculated from a UNICAST ADDRESS
How to generate a SOLICITED-NODE Multicast Address
Note the automatically joined group addresses for this IPv6 Interface
NEIGHBOR DISCOVERY PROTOCOL (NDP)
-
NEIGHBOR DISCOVERY PROTOCOL (NDP) is a PROTOCOL used with IPv6
-
It has various functions and one of those functions is to replace ARP, which is no longer used in IPv6
-
The ARP-like function of NDP uses ICMPv6 and SOLICITED-MODE Multicast Addresses to learn the MAC ADDRESS of other HOSTS (ARP in IPv4 uses Broadcast Messages)
-
TWO MESSAGES types are used:
-
- NEIGHBOR SOLICITATION (NS)
- ICMPv6 Type 135
-
- NEIGHBOR ADVERTISEMENT (NA)
- ICMPv6 Type 136
-
IPv6 NEIGHBOR TABLE
-
Another function of NDP allows HOSTS to automatically discover ROUTERS on the LOCAL NETWORK
-
TWO MESSAGES are used for this process:
-
ROUTER SOLICITATION (RS)
- ICMPv6 Type 133
- Sent to Multicast Address
FF02::2
(All Routers) - Asks ALL ROUTERS on the Local Link to identify themselves
- Sent when an INTERFACE is enabled / HOST is connected to the NETWORK
-
ROUTER ADVERTISEMENT (RA)
- ICMPv6 Type 134
- Sent to Multicast Address
FF02::1
(All Nodes) - The ROUTER announces its presence, as well as other information about the link
- These messages are sent in response to RS messages
- They are also sent periodically, even if the ROUTER hasn’t received an RS
-
SLAAC
- Stands for STATELESS ADDRESS AUTO-CONFIGURATION
- HOSTS use the RS / RA messages to learn the IPv6 Prefix of the LOCAL LINK (ie: 2000:db8:: /64) and then automatically generate an IPv6 Address
- Using the
ipv6 address prefix / prefix-length eui-64
command, you need to manually enter the prefix - Using the
ipv6 address autoconfig
command, you DON’T need to enter the prefix. The device uses NDP to learn the prefix used on the local link - The device will use EUI-64 to generate the INTERFACE ID or it will be randomly generated (depending on the device / maker)
DUPLICATE ADDRESS DETECTION (DAD)
- One final point about NDP!
- Duplicate Address Detection (DAD) allows HOSTS to check if other devices on the Local Link are using the same IPv6 Address
- Any time an IPv6-enabled interface initializes (
no shutdown
command) or an IPv6 ADDRESS is configured on an INTERFACE (by any method: manual, SLAAC, etc.) it performs DAD - DAD uses TWO MESSAGES you learned earlier : NS and NA
- The HOST will send an NS to its own IPv6 ADDRESS.
- If it doesn’t get a reply, it KNOWS the ADDRESS is unique
- If it DOES get a reply, it means ANOTHER HOST on the NETWORK is already using that ADDRESS
IPv6 STATIC ROUTING
- IPv6 ROUTING works the same as IPv4 ROUTING
- However, the TWO processes are separate on the ROUTER, and the TWO routing tables are separate, as well.
- IPv4 ROUTING is enabled BY DEFAULT
- IPv6 ROUTING is disabled BY DEFAULT
- MUST BE ENABLED with the
ipv6 unicast-routing
command
- MUST BE ENABLED with the
- If IPv6 ROUTING is disabled, the ROUTER will be able to SEND and RECEIVE IPv6 traffic, but will not route IPv6 traffic (ie: will NOT FORWARD it between NETWORKS)
- A CONNECTED NETWORK ROUTE is automatically added for EACH CONNECTED NETWORK
- A LOCAL HOST ROUTE is automatically added for each ADDRESS configured on the ROUTER
- Routes for Link-Local ADDRESSES are not added to the ROUTING TABLE
Everything is configured similar to normal static routes in IPv4
[AD] = Administrative Distance. You NEED this value in order to configure a STATIC ROUTE
DIRECTLY ATTACHED Static Route:
- Only the EXIT INTERFACE is specified
ipv6 route destination / prefix-length exit-interface
- Example :
~~R1(config)# ipv6 route 2001:db8:0:3:: /64 g0/0~~
RECURSIVE Static Route:
- Only the Next-Hop is specified
ipv6 route destination / prefix-length next-hop
- Example:
R1(config)# ipv6 route 2001:db8:0:3::/64 2001:db8:0:12::2
FULLY SPECIFIED Static Route:
- Both the Exit Interface and Next Hop are specified
ipv6 route destination / prefix-length exit-interface next-hop
- Example:
R1(config)# ipv6 route 2001:db8:0:3::/64 g0/0 2001:db8:0:12::2
(NOTE THAT THESE ROUTES ARE ALL RECURSIVE : They specify the Next-Hop)
NETWORK ROUTE:
R1(config)# ipv6 route 2001:db8:0::/64 2001:db8:0:12::2
This is a route to R3/PC2 NETWORK via R2’s G0/0 INTERFACE
(We did this in Day 32’s Lab)
HOST ROUTE:
R2(config)# ipv6 route 2001:db8:0:1::100/128 2001:db8:0:12::1
R2(config)# ipv6 route 2001:db8:0:3::100/128 2001:db8:0:23::2
This is a route from R2 to PC1 and PC2 using the “next hop” ADDRESSES of R1 and R3 G0/0 INTERFACES
Note the /128 prefix. This is how SPECIFIC IPv6 ADDRESSES are written
DEFAULT ROUTE:
R3(config)# ipv6 route ::/0 2001:db8:0:23::1
::/0 is the IPv6 equivalent of 0.0.0.0/0 in IPv4
FLOATING STATIC ROUTES:
- Require you to increase the [AD] number HIGHER than the currently used NETWORK IGP AD value
LINK-LOCAL NEXT HOPS:
You HAVE to specify the INTERFACE name when using Link-Local Next-Hops
This is EXACTLY like a FULLY-SPECIFIED STATIC ROUTE