ipv6 operations
DESCRIPTION
IPv6 Operations. Defining and Configuring Neighbor Discovery. ICMPv6. Next Header = 58 ICMPv6 Packet . ICMPv6 is similar to ICMPv4: Provides diagnostic and error messages Used for path MTU discovery. IPv6 Basic Header. ICMPv6 Packet. ICMPv6 Packet. ICMPv6 Type. ICMPv6 Code. Checksum. - PowerPoint PPT PresentationTRANSCRIPT
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© 2006 Cisco Systems, Inc. All rights reserved. IP6FD v2.0—2-1
IPv6 Operations
Defining and Configuring Neighbor Discovery
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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
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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
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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
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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
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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
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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 unique0 = 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
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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
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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
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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
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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
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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
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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
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Neighbor Discovery: Autoconfiguration
Autoconfiguration• Stateless
– Uses neighbor discovery router advertisements• Stateful
– Uses DHCPv6 service
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Routers send periodic router advertisements to the all-nodes multicast address.
Router advertisement packet definitions:ICMP type = 134Src = router link-local addressDst = all-nodes multicast addressData = options, prefix, lifetime, autoconfiguration flag
Router Advertisement
Neighbor Discovery: Router Advertisements
RouterAdvertisement
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Neighbor Discovery Parameters
Router advertisements:• Default router• IPv6 network prefix• Lifetime of advertisement
Autoconfiguring IPv6 Hosts
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Neighbor Discovery Parameters (Cont.)
Router advertisements:• Default router• IPv6 network prefix• Lifetime of advertisement
Autoconfiguring IPv6 Hosts
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Neighbor Discovery: Router Solicitations
At boot time, nodes send router solicitations to promptly receive router advertisements.
Router solicitation packet definitions:ICMP type = 133Src = unspecified addressDst = all-routers multicast address
RouterAdvertisement
Router Solicitation
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Stateless Autoconfiguration
Router solicitations are sent by booting nodes to request router advertisement for configuring the interfaces.
1. Router Solicitation:ICMP type = 133Src = ::Dst = all-routers multicastaddressQuery = Please send router advertisement
2. Routeradvertisement
1. Routersolicitation
2. Router Advertisement:ICMP type = 134Src = router link-local addressDst = all-nodes multicast addressData = options, prefix, lifetime, autoconfiguration flag
2. Routeradvertisement
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Router advertisement packet definitions:ICMP type = 134Src = Router link-local addressDst = All-nodes multicast addressData = Two prefixes:
Current prefix (to be deprecated) with short lifetimeNew 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
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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.
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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
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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
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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
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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
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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
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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:
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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.
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