Jeff Doyle -Vol 1: Chapter 2 Notes, IPV6 basics

IPV6 Rules: Leading 0’s can be omitted.

1 or more contiguous all-0’s can be replaced by ::

::/0 – Default route ; ::/128 – unspecified (used by NDP)

Global unicast address : (001 – first 3 bits => all addresses begin 2xxx::/4 or 3xxx::/4)

Starting addresses: 6bone – 3ffe, RIRs – 2001

Global routing Prefix (48)

Subnet ID (16)

Interface ID (64)

ð 65535 subnets

::1/128 – Loopback address; FF00::/8 – Multicast; FE80::/10 – Link-local unicast; FEC0::/10 – Site-local unicast

Anycast address: can be any global unicast address – represents a service (the override bit is always set to 0 in the NA)

Multicast

Multicast prefix 0xFF (8)

Flags (4)

Scope (4)

Group ID (112) Only last 32 used

Flags: First 3 bits unused; 0 = permanent, well known, 1 = temporary, admin assigned

Scope: 0×0 reserved, 0×1 node-local, 0×2 link-local, 0×5 site-local, 0×8 org-local, 0xE global

 

IPV6 Header: Always 40 octets.

Ver(4)	Traffic Class (8)	Flow Label (20)
Length (20)	Next Header (8)	Hop limit (8)
Source address
Destination Address

 

Extension Headers (Next Header) : Hop-by-hop (0), Routing (43), Fragment (44), ESP (50), AH (51), Destination Options (60), No Next Headers (59)

* Hard rule: If hop-hop is used, it should directly follow IPV6 header.

- NDP’s PnP Features: Router discovery, prefix discovery, parameter discover, address auto-config, address resolution (L2->L3), next-hop discovery (router or local n/w), Neighbor unreachability detection, Duplicate address discovery, Redirects.

ICMPv6 (protocol val = 58) is used for NDP. NDP messages are always link-local in scope and hop-limit is set to 255

RA: type 0, code 134, Source = Originator, Dest = unicast/ FF02::1 (all nodes m/c)

M – Managed address – stateful (DHCPv6) /stateless

O – Other stateful options

Router Lifetime: set to 0 if the router is not a default gateway

Reachable time: Instructs the host of neighbor reachability duration

Retransmit time: Instructs host of NS messages retransmit interval

Options: Link-layer i/f address, MTU, prefix info

—-

RS: type 0 , code 133, Source = Originator/ ::/128(no ip yet), Dest = FF02::2 (all routers )

——–

NS: type 0, code 135, Source = originator/ ::/128 (DaD), Dest = unicast/ Solicited-node m/c

—-

NA: type0, code 136, Source = originator, Dest = unicast/ FF02::1(announce new IP)

R- Router, S-solicited, O- override
—-
Redirect: type 0. code 137, source= router sending the redirect, Dest = unicast

Target = Better next hop, Dest = dest n/w for which target is the better next-hop

Options: set using TLVs ; Values = src-link address, target-link address, prefix-info, redirected header, MTU etc.

NDP Cisco configurable options:

ipv6 unicast-routing : automatically send RA on b/c media

ipv6 nd ra interval etc to influence the default settings

Address Auto-configuration: Prefix + mac-to-eui64 0xFFFE is inserted in the middle of the 48 bit mac and the 7^th bit U/L is flipped to 1 (Universal)

Duplicate Address Detection:

1. New address is classified “tentative”
2. NS -> Dest = Solicited-node m/c address : FF02:0:0:0:0:1:FF::/104

Src = ::/128, target = new address

1. Conflict => NA to NS requestor

Neighbor address resolution: DNS query -> <- response with /128 bit address, identifies if it is a link-local address or not (in which case it sends it to the router – known from RA).

1. looks up neighbor cache, if absent
2. enters the address, marks it INCOMPLETE
3. sends a NS to the solicited node m/c of the target
4. If there is no NA for 3 NS queries, resolution fails. Else the neighbor cache is updated, status : REACHABLE

Privacy addresses: RFC 3401 – to prevent users from being tracked, pseudo random i/f ID

Neighbor cache states: INCOMPLETE, REACHABLE, STALE (reachability time expired), PROBE (to re-establish reachability) sent after a DELAY

Neighbor Unreachability Detection: Two way confirmation – Either upper layer hints or NS in response to a NA or RA (with “s” set)