CIT 384: Network Administration Slide #1

CIT 384: Network Administration

IPv6

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Topics

1. Why IPv6?

2. IPv6 Addressing

3. Stateless autoconfiguration

4. Special Addresses

5. IPv4 to IPv6 Transition

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Why IPv6?

We’re running out of IP addresses– IPv4 lifetime extended by CIDR and NAT.– Only 14% of addresses are unallocated.– At current rate, all addresses used by 2011.

Solutions– Reclamation: reclaim unused/underused spaces.

• We allocate a /8 every few months, so too slow.

• Address space fragmentation increasing rtr table sizes.

– Upgrade to IPv6 with its 128-bit addresses.

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IPv4 to IPv6 Transition

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IPv4 to IPv6 Transition

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Why IPv6?

Security– IPsec is part of IPv6 backported to IPv4.

Mobility– Better support for mobile devices.

QoS– Support for multimedia QoS features.

Header Improvements– No need to recalculate checksum at each hop.

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IPv4 vs IPv6 Addresses

Feature IPv4 IPv6

Size of Address 32 bits 128 bits

Example Address 10.1.1.1 0000:0000:0000:0000:FFFF:FFFF:0A01:0101

Abbreviated Address

- ::FFFF:FFFF:0A01:0101

Localhost 127.0.0.1 ::1/128

Possible Addresses

232 (~4 billion) 2128 (~3.4 x 1038)

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IPv4 and IPv6 Address Composition

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IPv6 Prefixes

Prefix Explanation

2000::/3 All addresses whose first 3 bits are equal to the first 3 bits of 2000

2340:1140::/26 All addresses whose first 26 bits match 2340:1140

2340:1111::/32 All addresses whose first 32 bits match 2340:1111

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Global Route Aggregation

• Grouping by geographic region

• Grouping by ISP within geographic region

• Grouping by customer within ISP

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Global Routes Example

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IPv6 Prefix Assignment Example

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Subnetting IPv6 Addresses

Company 1 is assigned a /48Needs 4 subnetsUses 16 of the 80 provided bits for subnets.

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Subnetting IPv6 Addresses

Possible subnets: 216

Possible hosts/subnet: 264

Allows use of automatic IPv6 address assignment.

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IPv6 Address Format with EUI-64

Autoconfigure IPv6 addr using MAC

EUI-64 = MAC + FFEEUniversal/Local bit: 1=local, 0=burned in MAC

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Stateless Autoconfiguration

Use Neighbor Discovery Protocol (NDP)– Router solicitation (RS) multicast messages– Router responds with IPv6 prefix, router IPv6– IPv6 = IPv6_prefix + EUI-64– Another part of NDP replaces ARP

DHCPv6 is stateful alternative– Works like DHCP for IPv4– Must maintain client state (leases)– Can use stateless DHCP to provide DNS servers

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IPv6 Address Types

Unicast– Unicast addresses like IPv4.

Multicast– Represents a group of devices.

Anycast– Used when message can be sent to any member

of a group but does not need to be sent to all.

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IPv6 Special Addresses

Reserved AddressesAddrs beginning with 00 are reserved.

1/256 of entire address space.

Private AddressesAddrs beginning with FE[8-F] are private

Similar to RFC 1918 IPv4 private addresses.

Loopback Address0:0:0:0:0:0:0:1 is the one and only loopback addr

Unspecified Address0:0:0:0:0:0:0:0 used when a dev does not know own addr

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Private Address Types

Site Local– Scope is an entire site or network.– Local routers will fwd, internet routers will not.– Begin with FE[C-F]

Link Local– Scope is local subnet.– Routers will not fwd link local addresses.– Used for address configuration, resolution, ND.– Begin with FE[8-B]

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Stateless Autoconfiguration Process

1. Host computes its IPv6 link local address.2. Host sends an NDP router solicitation (RS)

Source addr: link local addressDest addr: FF02::2 all-routers multicast

3. Routers reply w/ router advertisement (RA)Reply includes prefix + router IP address

4. Host builds its unicast IP address1. Prefix from RA + EUI-642. Host asks stateless DHCP svr for DNS svr IPs

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IPv6 Routing Protocols

Routing protocol updates– Support for larger IPv6 addresses.

– Use of IPv6 multicast addresses

– Advertise link local IP as next hop.

Protocol Full Name RFC

RIPng RIP next generation 2080

OSPFv3 OSPF version 3 2740

MP-BGP4 Multiprocol BGP-4 2545/4760

EIGRP for IPv6 EIGRP for IPv6 Cisco

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IPv6 Transition

Dual Stacks– Devices that use both IPv4 and IPv6 at once.– Can use both protocols during transition.– Useful for intranets.

Tunneling– Encapsulate IPv6 packets in IPv4 packets.– Manual tunnels can be configured btw routers.– Dynamic 6to4 tunnels can be created as needed

using public 6to4 relay routers.

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IPv6 to IPv4 Tunnel

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NAT-PT

NAT-Protocol Translation– Translates IPv4/6 addresses at boundary.– Dynamically assigns IPv4 addrs to IPv6 nodes.– Needs a pool of IPv4 addresses.– Can use PAT for greater efficiency.

ALGs (Application Level Gateways)– Some protocols embed IPs w/i payload.– NAT-PT must use ALGs for DNS, FTP, etc.

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Transition Problems

• IPv6 is incompatible with IPv4

• Not every site is reachable with IPv6.

• Every site will need some IPv4 addresses.– NAT is going to stay with us for some time.

• Routers don’t support IPv6 in hardware.– Software routing is slower than hardware.

• Home routers/cable modems don’t do IPv6

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Key Topics

IPv6 Addresses– 128-bit addresses: 64-bit network, 64-bit host– Global route aggregation– Site local and link local addresses– Stateless autoconfiguration with EUID-64

IPv4 to IPv6 Transition– Dual Stacks– Tunnels– NAT-PT

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References1. Randy Bush, IPv6 Transition & Operational Reality,

http://www.nanog.org/mtg-0710/presentations/Bush-v6-op-reality.pdf, 2007.

2. Cisco, Cisco Connection Documentation, http://www.cisco.com/univercd/home/home.htm

3. Cisco, Internetworking Basics, http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/introint.htm

4. Silvia Hagan, IPv6 Essentials, O’Reilly, 2002.5. Charles M. Kozierok, The TCP/IP Guide, No Starch Press, 2005.6. IPv4 Address Report, http://www.potaroo.net/tools/ipv4/index.html7. Wendell Odom, CCNA Official Exam Certification Library, 3rd

edition, Cisco Press, 2007.