我有一個家庭 wifi 網絡，有 2 個 linux 和 1 個 mac 系統。我可以從 mac 和其他方式存取每個 linux，但嘗試從另一個 linux ping 一個 linux 會在兩個系統上出現「目標主機無法存取」錯誤。
可能是什麼原因造成的，以及如何解決？我禁用了兩個 Linux 系統上的所有防火牆：
iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
但這並沒有太大幫助。
細節：
電腦（Ubuntu 16.04）：
ifconfig:
wlp2s0 Link encap:Ethernet HWaddr ac:7b:a1:c5:ea:0e
inet addr:192.168.1.83 Bcast:192.168.1.255 Mask:255.255.255.0
route:
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.254 0.0.0.0 UG 600 0 0 wlp2s0
192.168.1.0 * 255.255.255.0 U 600 0 0 wlp2s0
arp:
Address HWtype HWaddress Flags Mask Iface
192.168.1.254 ether 58:90:43:49:eb:6b C wlp2s0
192.168.1.77 ether 34:02:86:aa:89:85 C wlp2s0
192.168.1.69 ether 18:65:90:dc:04:55 C wlp2s0
筆記型電腦（ubuntu 16.04）：
ifconfig:
wlan0 Link encap:Ethernet HWaddr 34:02:86:aa:89:85
inet addr:192.168.1.77 Bcast:192.168.1.255 Mask:255.255.255.0
route:
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.254 0.0.0.0 UG 600 0 0 wlan0
192.168.1.0 * 255.255.255.0 U 600 0 0 wlan0
arp:
Address HWtype HWaddress Flags Mask Iface
192.168.1.83 ether ac:7b:a1:c5:ea:0e C wlan0
192.168.1.69 ether 18:65:90:dc:04:55 C wlan0
192.168.1.254 ether 58:90:43:49:eb:6b C wlan0
蘋果電腦（10.13.3）：
ifconfig:
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 18:65:90:dc:04:55
inet6 fe80::80f:e846:2fe6:90c5%en0 prefixlen 64 secured scopeid 0x5
inet 192.168.1.69 netmask 0xffffff00 broadcast 192.168.1.255
route:
Destination Gateway Flags Refs Use Netif Expire
default 192.168.1.254 UGSc 105 0 en0
192.168.1 link#5 UCS 4 0 en0
192.168.1.69/32 link#5 UCS 0 0 en0
192.168.1.77 34:2:86:aa:89:85 UHLWI 0 510 en0 1154
192.168.1.83 ac:7b:a1:c5:ea:e UHLWIi 2 55 en0 915
192.168.1.254/32 link#5 UCS 1 0 en0
192.168.1.254 58:90:43:49:eb:6b UHLWIir 39 14075 en0 1169
192.168.1.255 ff:ff:ff:ff:ff:ff UHLWbI 0 2 en0
255.255.255.255/32 link#5 UCS 0 0 en0
從 PC 到 Mac 的 Ping 運作正常：
ping 192.168.1.69
PING 192.168.1.69 (192.168.1.69) 56(84) bytes of data.
64 bytes from 192.168.1.69: icmp_seq=1 ttl=64 time=6.15 ms
從 PC 到筆記型電腦的 Ping 操作不會：
ping 192.168.1.77
PING 192.168.1.77 (192.168.1.77) 56(84) bytes of data.
From 192.168.1.83 icmp_seq=9 Destination Host Unreachable
從筆記型電腦到 Mac 的 Ping 工作正常：
ping 192.168.1.69
PING 192.168.1.69 (192.168.1.69) 56(84) bytes of data.
64 bytes from 192.168.1.69: icmp_seq=1 ttl=64 time=5.89 ms
從筆記型電腦到 PC 的 Ping 操作不會：
ping 192.168.1.83
PING 192.168.1.83 (192.168.1.83) 56(84) bytes of data.
From 192.168.1.77 icmp_seq=2 Destination Host Unreachable
從 mac 到 pc 的 Ping 運作正常：
ping 192.168.1.83
PING 192.168.1.83 (192.168.1.83): 56 data bytes
64 bytes from 192.168.1.83: icmp_seq=0 ttl=64 time=101.836 ms
從 Mac 到筆記型電腦的 Ping 操作也有效：
ping 192.168.1.77
PING 192.168.1.77 (192.168.1.77): 56 data bytes
64 bytes from 192.168.1.77: icmp_seq=0 ttl=64 time=16.749 ms
來自 192.168.1.77 的 Tcpdump 期間telnet 192.168.83 22：
tcpdump -i wlan0 -s 65535 -n host 192.168.1.83
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlan0, link-type EN10MB (Ethernet), capture size 65535 bytes
18:38:53.194490 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 28
18:38:53.410085 ARP, Reply 192.168.1.83 is-at ac:7b:a1:c5:ea:0e, length 46
18:38:53.410100 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7583261 ecr 0,nop,wscale 7], length 0
18:38:54.193729 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7583511 ecr 0,nop,wscale 7], length 0
18:38:56.197662 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7584012 ecr 0,nop,wscale 7], length 0
18:39:00.205734 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7585014 ecr 0,nop,wscale 7], length 0
18:39:08.213738 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7587016 ecr 0,nop,wscale 7], length 0
18:39:24.245736 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7591024 ecr 0,nop,wscale 7], length 0
18:39:29.253720 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 28
18:39:30.253717 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 28
18:39:31.253715 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 28
18:39:56.309737 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 28
18:39:56.321748 ARP, Reply 192.168.1.83 is-at ac:7b:a1:c5:ea:0e, length 46
18:39:56.321762 IP 192.168.1.77.38208 > 192.168.1.83.22: Flags [S], seq 3257644438, win 29200, options [mss 1460,sackOK,TS val 7599040 ecr 0,nop,wscale 7], length 0
同時從192.168.1.83進行tcpdump：
tcpdump -i wlp2s0 -s 65535 -n host 192.168.1.77
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlp2s0, link-type EN10MB (Ethernet), capture size 65535 bytes
18:38:53.341294 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 46
18:38:53.341312 ARP, Reply 192.168.1.83 is-at ac:7b:a1:c5:ea:0e, length 28
18:39:56.316562 ARP, Request who-has 192.168.1.83 tell 192.168.1.77, length 46
18:39:56.316597 ARP, Reply 192.168.1.83 is-at ac:7b:a1:c5:ea:0e, length 28
更新
顯然我缺少一些智能設置英國電信智慧中心。一切都可以在不太複雜的路由器上運作。