【IPv6】IPV6 SLAAC地址分配过程及抓包分析

IPv6 SLAAC（无状态自动配置）

       主机可以通过RA（Router-Advertisement）消息ICMP type134中携带的前缀得到地址的前缀部分，同时通过该接口自动生成接口ID部分，从而得到一个完整的128位的IPV6地址，该消息默认情况下每200S发送一次。当然主机（或路由器）也可以主动发送RS（Router Solicit）消息ICMP Type=133来主动请求该前缀。

IPv6 SLAAC地址分配过程抓包分析

PC RS报文获取地址前缀，Type类型133

        为配置接口，主机需要前缀信息（类似于IPV4地址的网络部分），因此它会发送一条路由器请求（RouterSolicitation，RS）消息。该消息以组播方式发送给所有路由器。这实际上是一种ICMP消息，并用编号进行标识。PC发送RS(Router Solicitation)给到本地节点，所有路由器组播地址FF02::2，源地址和目的地址如下红色字体。

 Internet Protocol Version 6, Src: fe80::6d87:f0b:1be3:9972, Dst: ff02::2
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 16
    Next Header: ICMPv6 (58)
    Hop Limit: 255
    Source Address: fe80::6d87:f0b:1be3:9972
    Destination Address: ff02::2

Frame 335: 70 bytes on wire (560 bits), 70 bytes captured (560 bits)
Ethernet II, Src: 26:fc:27:b4:a6:a1 (26:fc:27:b4:a6:a1), Dst: IPv6mcast_02 (33:33:00:00:00:02)
Internet Protocol Version 6, Src: fe80::6d87:f0b:1be3:9972, Dst: ff02::2
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 16
    Next Header: ICMPv6 (58)
    Hop Limit: 255
    Source Address: fe80::6d87:f0b:1be3:9972
    Destination Address: ff02::2
Internet Control Message Protocol v6
    Type: Router Solicitation (133)
    Code: 0
    Checksum: 0x54f4 [correct]
    [Checksum Status: Good]
    Reserved: 00000000
    ICMPv6 Option (Source link-layer address : 26:fc:27:b4:a6:a1)
        Type: Source link-layer address (1)
        Length: 1 (8 bytes)
        Link-layer address: 26:fc:27:b4:a6:a1 (26:fc:27:b4:a6:a1)

路由设备回复RA，Type类型134

       路由器使用一条路由器通告（Router-Advertisement，RA）消息进行应答，其中包含请求的前级信息。RA消息也是组播分组，被发送到表示所有节点的组播地址，其ICMP类型为134。RA消息是定期发送的，但主机发送RS消息后，可立即得到响应，因此无需等待下一条定期发送的RA消息，就能获得所需的信息。

Frame 336: 158 bytes on wire (1264 bits), 158 bytes captured (1264 bits)
Ethernet II, Src: 96:ab:fd:96:d0:7d (96:ab:fd:96:d0:7d), Dst: 26:fc:27:b4:a6:a1 (26:fc:27:b4:a6:a1)
Internet Protocol Version 6, Src: fe80::a9f1:df9b:a5f6:b82d, Dst: fe80::6d87:f0b:1be3:9972
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 104
    Next Header: ICMPv6 (58)
    Hop Limit: 255
    Source Address: fe80::a9f1:df9b:a5f6:b82d
    Destination Address: fe80::6d87:f0b:1be3:9972
Internet Control Message Protocol v6
    Type: Router Advertisement (134)
    Code: 0
    Checksum: 0x23f9 [correct]
    [Checksum Status: Good]
    Cur hop limit: 255
    Flags: 0x40, Other configuration, Prf (Default Router Preference): Medium
    Router lifetime (s): 65535
    Reachable time (ms): 0
    Retrans timer (ms): 0
    ICMPv6 Option (Source link-layer address : 96:ab:fd:96:d0:7d)
        Type: Source link-layer address (1)
        Length: 1 (8 bytes)
        Link-layer address: 96:ab:fd:96:d0:7d (96:ab:fd:96:d0:7d)
    ICMPv6 Option (MTU : 1500)
        Type: MTU (5)
        Length: 1 (8 bytes)
        Reserved
        MTU: 1500
    ICMPv6 Option (Prefix information : 2408:8456:3204:dd45::/64)
        Type: Prefix information (3)
        Length: 4 (32 bytes)
        Prefix Length: 64
        Flag: 0xc0, On-link flag(L), Autonomous address-configuration flag(A)
        Valid Lifetime: Infinity (4294967295)
        Preferred Lifetime: Infinity (4294967295)
        Reserved
        Prefix: 2408:8456:3204:dd45::
    ICMPv6 Option (Recursive DNS Server fe80::94ab:fdff:fe93:cd7a fe80::94ab:fdff:fe93:cd7a)
        Type: Recursive DNS Server (25)
        Length: 5 (40 bytes)
        Reserved
        Lifetime: Infinity (4294967295)
        Recursive DNS Servers: fe80::94ab:fdff:fe93:cd7a
        Recursive DNS Servers: fe80::94ab:fdff:fe93:cd7a

路由分配地址发送NS,消息类型Type=135,PC回复NA,消息类型Type=136

NS ，Type=135，分配地址2408:8456:3204:dd45:a5c2:1725:60cf:de87

 Internet Protocol Version 6, Src: fe80::a9f1:df9b:a5f6:b82d, Dst: ff02::1:ffcf:de87
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 32
    Next Header: ICMPv6 (58)
    Hop Limit: 255
    Source Address: fe80::a9f1:df9b:a5f6:b82d
    Destination Address: ff02::1:ffcf:de87

Frame 341: 86 bytes on wire (688 bits), 86 bytes captured (688 bits)
Ethernet II, Src: 96:ab:fd:96:d0:7d (96:ab:fd:96:d0:7d), Dst: IPv6mcast_ff:cf:de:87 (33:33:ff:cf:de:87)
Internet Protocol Version 6, Src: fe80::a9f1:df9b:a5f6:b82d, Dst: ff02::1:ffcf:de87
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 32
    Next Header: ICMPv6 (58)
    Hop Limit: 255
    Source Address: fe80::a9f1:df9b:a5f6:b82d
    Destination Address: ff02::1:ffcf:de87
Internet Control Message Protocol v6
    Type: Neighbor Solicitation (135)
    Code: 0
    Checksum: 0x9b6d [correct]
    [Checksum Status: Good]
    Reserved: 00000000
    Target Address: 2408:8456:3204:dd45:a5c2:1725:60cf:de87
    ICMPv6 Option (Source link-layer address : 96:ab:fd:96:d0:7d)
        Type: Source link-layer address (1)
        Length: 1 (8 bytes)
        Link-layer address: 96:ab:fd:96:d0:7d (96:ab:fd:96:d0:7d)

NA，Type=136，PC回复使用地址2408:8456:3204:dd45:a5c2:1725:60cf:de87

Internet Protocol Version 6, Src: 2408:8456:3204:dd45:a5c2:1725:60cf:de87, Dst: fe80::a9f1:df9b:a5f6:b82d
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 32
    Next Header: ICMPv6 (58)
    Hop Limit: 255
    Source Address: 2408:8456:3204:dd45:a5c2:1725:60cf:de87
    Destination Address: fe80::a9f1:df9b:a5f6:b82d
Internet Control Message Protocol v6
    Type: Neighbor Advertisement (136)
    Code: 0
    Checksum: 0xd24f [correct]
    [Checksum Status: Good]
    Flags: 0x60000000, Solicited, Override
        0... .... .... .... .... .... .... .... = Router: Not set
        .1.. .... .... .... .... .... .... .... = Solicited: Set
        ..1. .... .... .... .... .... .... .... = Override: Set
        ...0 0000 0000 0000 0000 0000 0000 0000 = Reserved: 0
    Target Address: 2408:8456:3204:dd45:a5c2:1725:60cf:de87
    ICMPv6 Option (Target link-layer address : 26:fc:27:b4:a6:a1)
        Type: Target link-layer address (2)
        Length: 1 (8 bytes)
        Link-layer address: 26:fc:27:b4:a6:a1 (26:fc:27:b4:a6:a1)

地址分配过程

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