© 2006 Cisco Systems, Inc. All rights reserved.IP6FD v2.0—2-1 IPv6 Operations Defining and...
-
Upload
macie-rustan -
Category
Documents
-
view
219 -
download
2
Transcript of © 2006 Cisco Systems, Inc. All rights reserved.IP6FD v2.0—2-1 IPv6 Operations Defining and...
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-1
IPv6 Operations
Defining and Configuring Neighbor Discovery
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-2
ICMPv6
ICMPv6 is similar to ICMPv4:• Provides diagnostic and error messages
• Used for path MTU discovery
ICMPv6 Type ICMPv6 Code
ICMPv6 Data
Checksum
IPv6 Basic Header
ICMPv6 Packet
Next Header = 58 ICMPv6 Packet
ICMPv6 Packet
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-3
MTU = 1300
Path MTU Discovery
MTU = 1500
MTU = 1500
MTU = 1400
Packet with MTU = 1500
ICMP error: packet too big Use MTU = 1400
Packet with MTU = 1400
ICMP error: packet too big Use MTU = 1300
Packet with MTU = 1300
Path MTU = 1300
Source Destination
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-4
Maximum Transmission Unit
• IPv4
– MTU >= 68 octets
• IPv6
– MTU >= 1280 octets
– Path MTU used
Frame Header Frame TrailerIPv6 Packet
Minimum MTU = 1280 Octets
Link-Layer Frame
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-5
IPv6 over Data Link Layers
IPv6 is defined for most data link layers:• Ethernet
• PPP
• FDDI
• Token Ring
• HDLC
• Nonbroadcast multiaccess
• ATM
• Frame Relay
• IEEE 1394
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-6
IPv6 over Ethernet
IPv6 has a specific Ethernet protocol ID that is different from the protocol ID in IPv4.
Destination Ethernet Address
IPv6 Header and Payload0x86DDSource
Ethernet Address
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-7
000000X0
02
00 90 27
00 90 27
90 27
17 FC 0F
17 FC 0F
FF FE
Modified EUI-64 Format
A modified EUI-64 address is formed by inserting "FFFE" and “complementing” a bit identifying the uniqueness of the MAC address.
where X =1 = universally unique
0 = locally uniqueX = 1
Ethernet MAC Address (48 Bits)
64-Bit Version
U/L Bit
Modified EUI-64 Address
00 90 27
17 FC 0F
17 FC 0FFF FE
FF FE
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-8
Neighbor Discovery
• Neighbor discovery:
– Queries for duplicate address detection
– Determines the link layer address of a neighbor on the same link
– Finds neighbor routers on link
• Achieved by using ICMPv6 with IPv6 multicast
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-9
Solicited-Node Multicast Address
Solicited-node address:• Multicast address with a link-local scope
• Formed by a prefix and the rightmost 24 bits of every unicast and anycast address
Prefix
0 Lower 24
Interface ID
FF02
128 Bits
FF
24 Bits
IPv6 Address
Solicited-Node Multicast Address0001
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-10
FF02 0000 0000 0000 0000 0001
33 33
FF17 FC0F
17 FC 0FFF
Multicast Mapping over Ethernet
IPv6 Solicited-Node Multicast Address
Corresponding Ethernet Address
Multicast Prefix for Ethernet
Multicast
2001 0DB8 1001 000F 02C0 10FF FC0FIPv6 Address FE 17
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-11
Duplicate Address Detection
ICMP type = 135 Src = 0 (::) Dst = solicited-node multicast of A Data = link-layer address of A Query = What is your link address?
DAD uses neighbor solicitation to verify the existence of an address to be configured.
BA
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-12
ICMP type = 136 Src = B Dst = A Data = link-layer address of B
ICMP type = 135 Src = A Dst = solicited-node multicast of B Data = link-layer address of A Query = What is your link address?
A and B can now exchange
packets on this link.
Neighbor Discovery: Neighbor Solicitation
BA
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-13
Neighbor Discovery: Neighbor Solicitation (Cont.)
Neighbor Advertisement Message• R: router flag, indicates sender is a router
• S: solicited flag, indicates message sent in response to a neighbor solicitation
• O: override flag, indicates advertisement should override existing neighbor cache entry
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-14
Neighbor Discovery: Autoconfiguration
Autoconfiguration• Stateless
– Uses neighbor discovery router advertisements
• Stateful
– Uses DHCPv6 service
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-15
Routers send periodic router advertisements to the all-nodes multicast address.
Router advertisement packet definitions:
ICMP type = 134
Src = router link-local address
Dst = all-nodes multicast address
Data = options, prefix, lifetime, autoconfiguration flag
Router Advertisement
Neighbor Discovery: Router Advertisements
RouterAdvertisement
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-16
Neighbor Discovery Parameters
Router advertisements:• Default router
• IPv6 network prefix
• Lifetime of advertisementAutoconfiguring IPv6 Hosts
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-17
Neighbor Discovery Parameters (Cont.)
Router advertisements:• Default router
• IPv6 network prefix
• Lifetime of advertisementAutoconfiguring IPv6 Hosts
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-18
Neighbor Discovery: Router Solicitations
At boot time, nodes send router solicitations to promptly receive router advertisements.
Router solicitation packet definitions:
ICMP type = 133
Src = unspecified address
Dst = all-routers multicast address
RouterAdvertisement
Router Solicitation
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-19
Stateless Autoconfiguration
Router solicitations are sent by booting nodes to request router advertisement for configuring the interfaces.
1. Router Solicitation:
ICMP type = 133
Src = ::
Dst = all-routers multicastaddress
Query = Please send router advertisement
2. Routeradvertisement
1. Routersolicitation
2. Router Advertisement:
ICMP type = 134
Src = router link-local address
Dst = all-nodes multicast address
Data = options, prefix, lifetime, autoconfiguration flag
2. Routeradvertisement
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-20
Router advertisement packet definitions:
ICMP type = 134
Src = Router link-local address
Dst = All-nodes multicast address
Data = Two prefixes:
Current prefix (to be deprecated) with short lifetime
New prefix (to be used) with normal lifetime
Renumbering
Renumbering is achieved by modifying the router advertisement to announce the old prefix with a short lifetime and the new prefix.
RouterAdvertisement
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-21
Value of Autoconfiguration
• IPv6 address autoconfiguration enables “plug-and-play.”
• Nodes may be deployed without a DHCPv6 server:
– Mobile devices (phones, PDAs, autos)
– Home electronics (TVs, DVRs, appliances)
– Field telemetry (oil pipeline gauges)
• Autoconfiguration enables massive deployment (millions) of IPv6 nodes.
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-22
ipv6 nd prefix <prefix> | default [ [<valid-lifetime> <preferred-lifetime>] | [at <valid-date> <preferred-date>] [off-link] [no-autoconfig] ]
router(config-if)#
• Used to modify prefix advertisement parameters on an interface from their default values.
Cisco IOS Neighbor Discovery Command Syntax
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-23
LAN2: 2001:db8:c18:2::/64
LAN1: 2001:db8:c18:1::/64
Router Advertisement
Ethernet1
Ethernet0
Ethernet0
interface Ethernet0 ipv6 address 2001:db8:c18:1::2/64 ipv6 nd prefix 2001:db8:c18:1::/64 2000 1800
interface Ethernet1 ipv6 address 2001:db8:c18:2::1/64 ipv6 nd prefix 2001:db8:c18:2::/64 2000 1800
interface Ethernet0 ipv6 address 2001:db8:c18:1::1/64 ipv6 nd prefix 2001:db8:c18:1::/64 2000 1800
Router2
Router1
Cisco IOS Command for Overriding the Neighbor Discovery Defaults
Router Advertisement
IPv6 Internet
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-24
LAN1: 2001:db8:c18:1::/64
LAN2: 2001:db8:c18:2::/64
Ethernet0
Ethernet1
Ethernet0
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 2000 1800
interface Ethernet1 ipv6 nd prefix 2001:db8:c18:2::/64 2000 1800
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 2000 1800
Router2
Router1
Cisco IOS Command for Overriding the Neighbor Discovery Defaults (Cont.)
Router Advertisement
Router Advertisement
IPv6 Internet
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-25
LAN1: 2001:db8:c18:1::/64
LAN2: 2001:db8:c18:2::/64
Ethernet0
Ethernet1
Ethernet0
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 43200 43200 ipv6 nd ra lifetime 100
interface Ethernet1 ipv6 nd prefix 2001:db8:c18:2::/64 43200 43200
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 43200 43200
Router2
Router1
Cisco IOS Neighbor Discovery Lifetimes
Router Advertisement
Router Advertisement
IPv6 Internet
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-26
Network Prefix: 2001:db8:c18:1::/64
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 43200 43200
Host Configuration:Autoconfiguring IPv6 Hosts preferred address 2001:db8:c18:1:260:8ff:fede:8fbe
Router Configuration before Renumbering:
Router Advertisements
Cisco IOS Network Prefix Renumbering Scenario
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-27
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 43200 0 ipv6 nd prefix 2001:db8:c18:2::/64 43200 43200
New Network Prefix: 2001:db8:c18:2::/64Deprecated Prefix: 2001:db8:c18:1::/64
Host Configuration:
Autoconfiguring IPv6 Hosts
deprecated address 2001:db8:c18:1:260:8ff:fede:8fbepreferred address 2001:db8:c18:2:260:8ff:fede:8fbe
Router Configuration after Renumbering:
Router Advertisements
interface Ethernet0 ipv6 nd prefix 2001:db8:c18:1::/64 at Jul 31 2002 23:59 Jul 1 2002 23:59 ipv6 nd prefix 2001:sb8:c18:2::/64 43200 43200
Cisco IOS Network Prefix Renumbering Scenario (Cont.)
or:
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-28
Summary
• ICMP messages are used for many IPv6 functions, including path MTU discovery, neighbor discovery, and router discovery. ICMPv6 is an integral part of IPv6 but looks similar to a Layer 4 protocol, much like TCP or UDP.
• Path MTU is performed by nodes in an effort to determine the largest packet size they can send to a given destination. It is based on a process of sending large packets and listening for ICMPv6 error messages.
• Neighbor discovery is a critical process that allows neighbors to determine the link-layer address associated with a given IPv6 address. It also allows hosts to receive prefix information to configure a global-scope address and find the default router.
• Before a node can use an address, it must test it for uniqueness on the link. DAD is a process by which a node with a "tentative" address that it would like to use determines if that address is already in use.
• Autoconfiguration provides a type of network “plug-and-play,” easily supporting millions of transient nodes and enabling a network environment with support for mobile phones, field sensors, and home appliances.
• Cisco routers are IPv6-ready and are configured for IPv6 functions on a global and per-interface basis, depending on the function being enabled.
© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-29