Linux IPv6 address configuration的思考

默认情况下，现在常用的Linux发型版本都支持IPV6，且同时激活。

此时，如果网络中有一个IPV6的网络设备正在执行ND操作，发送RS消息，linux机器自动回应RA消息，同时，该接口使用IPV6的autoconfiguration功能，自行配置上IPV6地址。

如果该Linux interface收到多个网段的IPV6 RS消息，则，同步会配置上多个IPV6地址。

如：

[asr@Fedora-30-103 ~]$ ifconfig
em1       Link encap:Ethernet  HWaddr 00:15:17:8C:43:B8
inet addr:10.74.30.103  Bcast:10.74.30.255  Mask:255.255.255.0
inet6 addr: 10:74:30:0:215:17ff:fe8c:43b8/64 Scope:Global
inet6 addr: fe80::215:17ff:fe8c:43b8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:470 errors:0 dropped:0 overruns:0 frame:0
TX packets:275 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:58057 (56.6 KiB)  TX bytes:49415 (48.2 KiB)
Interrupt:18 Memory:b8820000-b8840000

em2       Link encap:Ethernet  HWaddr 00:15:17:8C:43:B9
inet addr:40.0.0.2  Bcast:40.0.0.255  Mask:255.255.255.0
inet6 addr: 2003::215:17ff:fe8c:43b9/64 Scope:Global
inet6 addr: fe80::215:17ff:fe8c:43b9/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:19 errors:0 dropped:0 overruns:0 frame:0
TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5514 (5.3 KiB)  TX bytes:6355 (6.2 KiB)
Interrupt:19 Memory:b8800000-b8820000

lo        Link encap:Local Loopback
inet addr:127.0.0.1  Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING  MTU:16436  Metric:1
RX packets:30 errors:0 dropped:0 overruns:0 frame:0
TX packets:30 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1952 (1.9 KiB)  TX bytes:1952 (1.9 KiB)

p6p1      Link encap:Ethernet  HWaddr 00:15:17:CB:6D:FC
UP BROADCAST MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
Interrupt:16 Memory:b8c60000-b8c80000

p6p2      Link encap:Ethernet  HWaddr 00:15:17:CB:6D:FD
inet addr:9.2.1.1  Bcast:9.2.1.255  Mask:255.255.255.0
          inet6 addr: 2001::215:17ff:fecb:6dfd/64 Scope:Global
inet6 addr: 2002::215:17ff:fecb:6dfd/64 Scope:Global
inet6 addr: 2003::215:17ff:fecb:6dfd/64 Scope:Global
inet6 addr: fe80::215:17ff:fecb:6dfd/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:176 errors:0 dropped:0 overruns:0 frame:0
TX packets:59 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:23261 (22.7 KiB)  TX bytes:11173 (10.9 KiB)
Interrupt:17 Memory:b8c20000-b8c40000

p6p3      Link encap:Ethernet  HWaddr 00:15:17:CB:6D:FE
inet addr:5.1.1.11  Bcast:5.1.1.255  Mask:255.255.255.0
inet6 addr: 2003::215:17ff:fecb:6dfe/64 Scope:Global
inet6 addr: fe80::215:17ff:fecb:6dfe/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:13 errors:0 dropped:0 overruns:0 frame:0
TX packets:25 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2613 (2.5 KiB)  TX bytes:5854 (5.7 KiB)
Interrupt:17 Memory:b8b60000-b8b80000

p6p4      Link encap:Ethernet  HWaddr 00:15:17:CB:6D:FF
inet addr:9.4.1.1  Bcast:9.4.1.255  Mask:255.255.255.0
inet6 addr: fe80::215:17ff:fecb:6dff/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:22 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b)  TX bytes:5574 (5.4 KiB)
Interrupt:18 Memory:b8b20000-b8b40000

virbr0    Link encap:Ethernet  HWaddr 66:6B:A9:7D:1C:C2
inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:17 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b)  TX bytes:4294 (4.1 KiB)

[asr@Fedora-30-103 ~]$

此时，Linux的路由表将变得非常复杂，夹杂着静态路由在一起，让人眼花缭乱。

[asr@Fedora-30-103 ~]$ ip -6 route show
10:74:30::/64 dev em1  proto kernel  metric 256  expires 2147157sec
2001::/64 dev p6p2  proto kernel  metric 256  expires 2147157sec
2002::/64 dev p6p2  proto kernel  metric 256  expires 2147157sec
2003::/64 dev p6p2  proto kernel  metric 256  expires 2147157sec
2003::/64 dev em2  proto kernel  metric 256  expires 2147157sec
2003::/64 dev p6p3  proto kernel  metric 256  expires 2147157sec
unreachable fe80::/64 dev lo  proto kernel  metric 256  error -101
fe80::/64 dev p6p2  proto kernel  metric 256
fe80::/64 dev em1  proto kernel  metric 256
fe80::/64 dev em2  proto kernel  metric 256
fe80::/64 dev p6p3  proto kernel  metric 256
fe80::/64 dev p6p4  proto kernel  metric 256
default via fe80::1edf:fff:feb1:f991 dev p6p2  proto kernel  metric 1024  expires 1765sec hoplimit 64
default via fe80::1edf:fff:feb1:f991 dev em2  proto kernel  metric 1024  expires 1765sec hoplimit 64
default via fe80::1edf:fff:feb1:f991 dev p6p3  proto kernel  metric 1024  expires 1765sec hoplimit 64
default via fe80::21e:beff:fef3:fbe0 dev em1  proto kernel  metric 1024  expires 1605sec hoplimit 64
default via fe80::1edf:fff:feb1:f992 dev p6p2  proto kernel  metric 1024  expires 1607sec hoplimit 64
default via fe80::224:97ff:fe6a:fe23 dev p6p2  proto kernel  metric 1024  expires 1721sec hoplimit 64
default via fe80::224:97ff:fe6a:fe24 dev p6p2  proto kernel  metric 1024  expires 1728sec hoplimit 64
[asr@Fedora-30-103 ~]$

此时，一种方法就是禁用Linux interface的自动配置功能，第二种就是明确网络中的IPV6地址分配，不用把Linux机器中的多个interface放在同一个网段中。

慎重！

否则，路由表一混乱，ping包收到后，回复的echo response将无法原路送回，导致ping永远不成功。