我用 Arch Linux 设置了一个简单的网关：
GATEWAY# ifconfig eth0 172.27.210.221 netmask 255.255.255.0
GATEWAY# ifconfig wlan0 10.8.221.221 netmask 255.255.0.0
GATEWAY# iwconfig wlan0 essid OpenWifi
GATEWAY# echo 1 > /proc/sys/net/ipv4/ip_forward
这是网关上的实际路由表：
DESTINATION GATEWAY GENMASK FLAGS METRIC REF USE IFACE
10.8.0.0 0.0.0.0 255.255.0.0 U 0 0 0 wlan0
172.27.210.0 0.0.0.0 255.255.255.0 U 202 0 0 eth0
我在所有接口上禁用了 rp_filter。
eth0 连接到我无法访问的交换机。当一切正常时，该接口将配置为访问互联网。wlan0 连接到开放的网络基础设施。
我有一台基于 Arch Linux 的客户端电脑，连接到同一个无线网络，设置如下：
CLIENT# iwconfig wlan0 essid OpenWifi
CLIENT# ifconfig wlan0 10.8.221.222 netmask 255.255.0.0
CLIENT# route add default gw 10.8.221.221 wlan0
现在，我知道要共享 Internet 连接，我需要添加默认路由并在网关计算机上设置 NAT。但我想我应该能够从我的客户端 ping 网关的 eth0 接口，而无需任何其他配置：
CLIENT# ping 172.27.210.221
问题是，我没有收到任何回复。
网关 wlan0 接口上的 tcpdump 显示 ICMP 请求传入，并且从 172.27.210.221 到 10.8.221.222 的回复，但实际上我没有在客户端上收到任何回复（我使用客户端上的 tcpdump 确认了这一点）。
如果我将此设置复制到两台虚拟机上，仅使用以太网接口，则完全没有问题。您知道可能是什么问题吗？这可能与无线网络有关吗？
更新 1
以下是从客户端 10.8.221.222 ping 网关 172.27.210.221 时，客户端和网关上 iwconfig wlan0、iptables -nvL 和 tcpdump -npe 的输出：
网关：
iwconfig wlp2s0b1
wlp2s0b1 IEEE 802.11 ESSID:"OpenWifi"
Mode:Managed Frequency:2.437 GHz Access Point: xxxxxxxxxxxx
Bit Rate=54 Mb/s Tx-Power=11 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=70/70 Signal level=-29 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:79 Invalid misc:772 Missed beacon:0
iptables -nvL
Chain INPUT (policy ACCEPT 172K packets, 22M bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 1132 packets, 95328 bytes)
pkts bytes target prot opt in out source destination
tcpdump -npe 'icmp'
03:29:23.876193 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 1, length 64
03:29:23.876277 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 1, length 64
03:29:24.893768 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 2, length 64
03:29:24.893842 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 2, length 64
03:29:25.908918 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 3, length 64
03:29:25.908999 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 3, length 64
03:29:26.920903 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 4, length 64
03:29:26.920969 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 4, length 64
03:29:27.933499 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 5, length 64
03:29:27.933618 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 5, length 64
03:29:28.944583 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 6, length 64
03:29:28.944650 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 6, length 64
03:29:29.958243 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 7, length 64
03:29:29.958323 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 7, length 64
03:29:30.971649 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 8, length 64
03:29:30.971744 yyyyyyyyyyyyyy > xxxxxxxxxxxxxx, ethertype IPv4 (0x0800), length 98: 172.27.210.221 > 10.8.221.222: ICMP echo reply, id 13006, seq 8, length 64
客户：
iwconfig wlp1s0
wlp1s0 IEEE 802.11 ESSID:"OpenWifi"
Mode:Managed Frequency:2.412 GHz Access Point: xxxxxxxxxxxx
Bit Rate=1 Mb/s Tx-Power=11 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:on
Link Quality=54/70 Signal level=-56 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:1 Invalid misc:26 Missed beacon:0
iptables -nvL
Chain INPUT (policy ACCEPT 1665 packets, 149K bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 765 packets, 64260 bytes)
pkts bytes target prot opt in out source destination
tcpdump -npe 'icmp'
12:29:30.950270 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 1, length 64
12:29:31.968238 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 2, length 64
12:29:32.981538 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 3, length 64
12:29:33.994868 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 4, length 64
12:29:35.008223 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 5, length 64
12:29:36.021575 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 6, length 64
12:29:37.034884 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 7, length 64
12:29:38.048205 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 8, length 64
12:29:39.061533 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 9, length 64
12:29:40.074884 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 10, length 64
12:29:41.088206 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 11, length 64
12:29:42.101534 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 12, length 64
12:29:43.114876 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 13, length 64
12:29:44.128193 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 14, length 64
12:29:45.141535 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 15, length 64
12:29:46.154870 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 16, length 64
12:29:47.168208 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 17, length 64
12:29:48.181573 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 18, length 64
12:29:49.194868 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 19, length 64
12:29:50.208171 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 20, length 64
12:29:51.221531 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 21, length 64
12:29:52.234870 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 22, length 64
12:29:53.248185 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 23, length 64
12:29:54.261521 xxxxxxxxxxxxxx > yyyyyyyyyyyyyy, ethertype IPv4 (0x0800), length 98: 10.8.221.222 > 172.27.210.221: ICMP echo request, id 13006, seq 24, length 64
答案1
您所描述的方法应该有效。
尝试禁用 iptables 并再次尝试 ping。