最后的突破-> 参见沙克下面的结果提供了一些线索
你好，我在家有以下设置：
互联网 - NAS (Ubuntu 16.04.4 LTS) - LAN (华硕 N56U WiFi) - 家庭用户。 NAS 连接使用PPPOE（ppp0，电缆）连接到 Internet，同时将 eth0（192.168.0.1，电缆）连接到 LAN。华硕 N56U 使用静态 IP 192.168.0.2/255.255.255.0 和 DNS 192.168.0.1 连接到 NAS。
一切正常：
NAS 和家庭用户访问 Internet，同时 Internet 访问 NAS。
我还有另一个极其相似的路由器（华硕 RT-AC66U），它只需与华硕 N56U 交换，同时保持同样简单的设置不起作用:(。我的意思是任何触摸尽管我的个人网站仍然可以通过 LAN 访问，但互联网已停止运行。
我在 NAS 上尝试了这个命令（108.177.119.94 是 www.google.ro）：
sudo tcpdump -AX -vnni eth0 -c 2 dst 108.177.119.94
在路由器上运行它时（我可以通过telnet访问它们）：
ping -c 2 108.177.119.94
我得到了 N56U 的这个：
09:00:47.036839 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
192.168.0.2 > 108.177.119.94: ICMP echo request, id 63814, seq 0, length 64
0x0000: 4500 0054 0000 4000 4001 95ef c0a8 0002 E..T..@.@.......
0x0010: 6cb1 775e 0800 d64a f946 0000 7cd9 ab94 l.w^...J.F..|...
0x0020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0030: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0050: 0000 0000 ....
09:00:48.044176 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
192.168.0.2 > 108.177.119.94: ICMP echo request, id 63814, seq 1, length 64
0x0000: 4500 0054 0000 4000 4001 95ef c0a8 0002 E..T..@.@.......
0x0010: 6cb1 775e 0800 95eb f946 0001 ad37 bb94 l.w^.....F...7..
0x0020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0030: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0050: 0000 0000 ....
对于 AC66U（有问题的）：
09:07:16.655875 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
192.168.0.2 > 108.177.119.94: ICMP echo request, id 27906, seq 0, length 64
0x0000: 4500 0054 0000 4000 4001 95ef c0a8 0002 E..T..@.@.......
0x0010: 6cb1 775e 0800 638c 6d02 0000 de6b 4905 l.w^..c.m....kI.
0x0020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0030: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0050: 0000 0000 ....
09:07:17.668123 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
192.168.0.2 > 108.177.119.94: ICMP echo request, id 27906, seq 1, length 64
0x0000: 4500 0054 0000 4000 4001 95ef c0a8 0002 E..T..@.@.......
0x0010: 6cb1 775e 0800 7e18 6d02 0001 b4de 5805 l.w^..~.m.....X.
0x0020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0030: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x0050: 0000 0000 ....
有了 N56U，我明白了（使用tcp转储) 请求从 eth0 通过 ppp0 传输到 Internet 并返回；对于 AC66U，我看到的就是上面的结果（请求由 eth0 接收，然后什么也没有）。
可能是什么问题？
编辑4 （下面我指出了一个可能存在的问题）
查看上述结果（已保存为 *.pcap 文件）的另一种方法是沙克（仅第 1 帧）。
对于 N56U 我得到：
$tshark -r n56u-eth0-dst.pcap -V
Frame 1: 98 bytes on wire (784 bits), 98 bytes captured (784 bits)
Encapsulation type: Ethernet (1)
Arrival Time: May 5, 2018 09:00:47.036839000 EEST
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1525500047.036839000 seconds
[Time delta from previous captured frame: 0.000000000 seconds]
[Time delta from previous displayed frame: 0.000000000 seconds]
[Time since reference or first frame: 0.000000000 seconds]
Frame Number: 1
Frame Length: 98 bytes (784 bits)
Capture Length: 98 bytes (784 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ethertype:ip:icmp:data]
Ethernet II, Src: Motorola_1b:ed:f2 (98:0c:a5:1b:ed:f2), Dst: AsrockIn_7c:28:bf (d0:50:99:7c:28:bf)
Destination: AsrockIn_7c:28:bf (d0:50:99:7c:28:bf)
Address: AsrockIn_7c:28:bf (d0:50:99:7c:28:bf)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: Motorola_1b:ed:f2 (98:0c:a5:1b:ed:f2)
Address: Motorola_1b:ed:f2 (98:0c:a5:1b:ed:f2)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 192.168.0.2, Dst: 108.177.119.94
0100 .... = Version: 4
.... 0101 = Header Length: 20 bytes (5)
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
0000 00.. = Differentiated Services Codepoint: Default (0)
.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
Total Length: 84
Identification: 0x0000 (0)
Flags: 0x02 (Don't Fragment)
0... .... = Reserved bit: Not set
.1.. .... = Don't fragment: Set
..0. .... = More fragments: Not set
Fragment offset: 0
Time to live: 64
Protocol: ICMP (1)
Header checksum: 0x95ef [validation disabled]
[Header checksum status: Unverified]
Source: 192.168.0.2
Destination: 108.177.119.94
[Source GeoIP: Unknown]
[Destination GeoIP: United States, AS15169 Google Inc., Mountain View, CA, 37.419201, -122.057404]
[Destination GeoIP Country: United States]
[Destination GeoIP AS Number: AS15169 Google Inc.]
[Destination GeoIP City: Mountain View, CA]
[Destination GeoIP Latitude: 37.419201]
[Destination GeoIP Longitude: -122.057404]
Internet Control Message Protocol
Type: 8 (Echo (ping) request)
Code: 0
Checksum: 0xd64a [correct]
[Checksum Status: Good]
Identifier (BE): 63814 (0xf946)
Identifier (LE): 18169 (0x46f9)
Sequence number (BE): 0 (0x0000)
Sequence number (LE): 0 (0x0000)
Data (56 bytes)
0000 7c d9 ab 94 00 00 00 00 00 00 00 00 00 00 00 00 |...............
0010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0030 00 00 00 00 00 00 00 00 ........
Data: 7cd9ab940000000000000000000000000000000000000000...
[Length: 56]
对于 AC66U 我得到：
$tshark -r ac66u-eth0-dst.pcap -V
Frame 1: 98 bytes on wire (784 bits), 98 bytes captured (784 bits)
Encapsulation type: Ethernet (1)
Arrival Time: May 5, 2018 09:07:16.655875000 EEST
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1525500436.655875000 seconds
[Time delta from previous captured frame: 0.000000000 seconds]
[Time delta from previous displayed frame: 0.000000000 seconds]
[Time since reference or first frame: 0.000000000 seconds]
Frame Number: 1
Frame Length: 98 bytes (784 bits)
Capture Length: 98 bytes (784 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ethertype:ip:icmp:data]
Ethernet II, Src: AsustekC_cb:20:d0 (2c:56:dc:cb:20:d0), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Destination: Broadcast (ff:ff:ff:ff:ff:ff)
Address: Broadcast (ff:ff:ff:ff:ff:ff)
.... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
.... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
Source: AsustekC_cb:20:d0 (2c:56:dc:cb:20:d0)
Address: AsustekC_cb:20:d0 (2c:56:dc:cb:20:d0)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 192.168.0.2, Dst: 108.177.119.94
0100 .... = Version: 4
.... 0101 = Header Length: 20 bytes (5)
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
0000 00.. = Differentiated Services Codepoint: Default (0)
.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
Total Length: 84
Identification: 0x0000 (0)
Flags: 0x02 (Don't Fragment)
0... .... = Reserved bit: Not set
.1.. .... = Don't fragment: Set
..0. .... = More fragments: Not set
Fragment offset: 0
Time to live: 64
Protocol: ICMP (1)
Header checksum: 0x95ef [validation disabled]
[Header checksum status: Unverified]
Source: 192.168.0.2
Destination: 108.177.119.94
[Source GeoIP: Unknown]
[Destination GeoIP: United States, AS15169 Google Inc., Mountain View, CA, 37.419201, -122.057404]
[Destination GeoIP Country: United States]
[Destination GeoIP AS Number: AS15169 Google Inc.]
[Destination GeoIP City: Mountain View, CA]
[Destination GeoIP Latitude: 37.419201]
[Destination GeoIP Longitude: -122.057404]
Internet Control Message Protocol
Type: 8 (Echo (ping) request)
Code: 0
Checksum: 0x638c [correct]
[Checksum Status: Good]
Identifier (BE): 27906 (0x6d02)
Identifier (LE): 621 (0x026d)
Sequence number (BE): 0 (0x0000)
Sequence number (LE): 0 (0x0000)
Data (56 bytes)
0000 de 6b 49 05 00 00 00 00 00 00 00 00 00 00 00 00 .kI.............
0010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0030 00 00 00 00 00 00 00 00 ........
Data: de6b49050000000000000000000000000000000000000000...
[Length: 56]
我猜这个部分（对于AC66U）：
Destination: Broadcast (ff:ff:ff:ff:ff:ff)
可能表明有问题？有什么线索吗？