以下是问题的简要概述。我无法与同一子网内的 Linux 网络命名空间通信。我在无头服务器上运行 Ubuntu 14.04.1 LTS。我已经对此进行了大约一周的故障排除，因此提前感谢您的回复。
从头开始：（底部有 tcpdump）
我有两个物理接口em1和em2。我创建了两个桥接器br0和br1。第一个桥接器br0包含我的外部接口em1。第二个桥接器br1包含我的内部接口em2和veth0（链接到如下所示的veth1网络命名空间中）。vpn
cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# Bridge setup
auto br0 em1
iface br0 inet dhcp
bridge_ports em1
auto br1 em2 veth0
iface br1 inet static
address 10.0.0.1
network 10.0.0.0
netmask 255.255.255.0
broadcast 10.0.0.255
bridge_ports em2 veth0
# pre and post up
pre-up ip link add name veth0 type veth peer name veth1
pre-up ip netns add vpn
pre-up ip link set veth1 netns vpn
post-up ip netns exec vpn ip link set dev lo up
post-up ip netns exec vpn ip link set dev veth1 up
post-up ip netns exec vpn ip addr add 10.0.0.254/24 broadcast 10.0.0.255 dev veth1
post-up ip netns exec vpn ip route add default via 10.0.0.1
我使用此服务器进行路由。这是我的 nat.sh，每次启动都会运行。
echo -e "\n\nLoading simple rc.firewall-iptables version $FWVER..\n"
DEPMOD=/sbin/depmod
MODPROBE=/sbin/modprobe
EXTIF="br0"
INTIF="br1"
#INTIF2="eth0"
echo " External Interface: $EXTIF"
echo " Internal Interface: $INTIF"
#======================================================================
#== No editing beyond this line is required for initial MASQ testing ==
echo -en " loading modules: "
echo " - Verifying that all kernel modules are ok"
$DEPMOD -a
echo "----------------------------------------------------------------------"
echo -en "ip_tables, "
$MODPROBE ip_tables
echo -en "nf_conntrack, "
$MODPROBE nf_conntrack
echo -en "nf_conntrack_ftp, "
$MODPROBE nf_conntrack_ftp
echo -en "nf_conntrack_irc, "
$MODPROBE nf_conntrack_irc
echo -en "iptable_nat, "
$MODPROBE iptable_nat
echo -en "nf_nat_ftp, "
$MODPROBE nf_nat_ftp
echo "----------------------------------------------------------------------"
echo -e " Done loading modules.\n"
echo " Enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward
echo " Enabling DynamicAddr.."
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
echo " Clearing any existing rules and setting default policy.."
iptables-restore <<-EOF
*nat
-A POSTROUTING -o "$EXTIF" -j MASQUERADE
COMMIT
*filter
:INPUT ACCEPT [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
-A FORWARD -i "$EXTIF" -o "$INTIF" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -i "$INTIF" -o "$EXTIF" -j ACCEPT
-A FORWARD -j LOG
COMMIT
EOF
echo -e "\nrc.firewall-iptables v$FWVER done.\n"
网络上的所有设备都有来自此服务器的地址，并且位于同一子网中。所有设备都能够完美地相互通信。我唯一的问题是，没有任何设备能够访问veth1网络命名空间vpn，尽管它像其他所有设备一样具有来自服务器的地址和子网，甚至可以 ping google。
例如，从我的笔记本电脑输入地址10.0.0.4。该命令ping 10.0.0.1有效，并且ping 10.0.0.3（我的 Xbox）有效。但ping 10.0.0.254不起作用，即使它与其他所有东西都在同一个网络上。
以下是一些附加信息：
sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1
cat /proc/sys/net/ipv4/ip_forward
1
ifconfig
br0 Link encap:Ethernet HWaddr 00:1e:67:ad:9e:1d
inet addr:71.95.217.302 Bcast:255.255.255.255 Mask:255.255.254.0
inet6 addr: fe80::21e:67ff:fead:9e1d/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:57249 errors:0 dropped:0 overruns:0 frame:0
TX packets:17297 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:13724815 (13.7 MB) TX bytes:2606039 (2.6 MB)
br1 Link encap:Ethernet HWaddr 00:1e:67:ad:9e:1e
inet addr:10.0.0.1 Bcast:10.0.0.255 Mask:255.255.255.0
inet6 addr: fe80::21e:67ff:fead:9e1e/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:17716 errors:0 dropped:0 overruns:0 frame:0
TX packets:18625 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2382424 (2.3 MB) TX bytes:11990075 (11.9 MB)
em1 Link encap:Ethernet HWaddr 00:1e:67:ad:9e:1d
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:58804 errors:0 dropped:0 overruns:0 frame:0
TX packets:17304 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:14632304 (14.6 MB) TX bytes:2606465 (2.6 MB)
Memory:b1200000-b1280000
em2 Link encap:Ethernet HWaddr 00:1e:67:ad:9e:1e
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:17636 errors:0 dropped:0 overruns:0 frame:0
TX packets:20125 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2639201 (2.6 MB) TX bytes:12086082 (12.0 MB)
Memory:b1100000-b1180000
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:65536 Metric:1
RX packets:4775 errors:0 dropped:0 overruns:0 frame:0
TX packets:4775 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:939016 (939.0 KB) TX bytes:939016 (939.0 KB)
veth0 Link encap:Ethernet HWaddr 4e:99:98:cc:48:6d
inet6 addr: fe80::4c99:98ff:fecc:486d/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:75 errors:0 dropped:0 overruns:0 frame:0
TX packets:1902 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:6799 (6.7 KB) TX bytes:140261 (140.2 KB)
brctl show br0
bridge name bridge id STP enabled interfaces
br0 8000.001e67ad9e1d no em1
brctl show br1
bridge name bridge id STP enabled interfaces
br1 8000.001e67ad9e1e no em2
veth0
ip route
default via 71.95.216.1 dev br0
10.0.0.0/24 dev br1 proto kernel scope link src 10.0.0.1
71.95.216.0/23 dev br0 proto kernel scope link src 71.95.217.302
route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 71-95-216-1.sta 0.0.0.0 UG 0 0 0 br0
10.0.0.0 * 255.255.255.0 U 0 0 0 br1
71.95.216.0 * 255.255.254.0 U 0 0 0 br0
ip netns exec vpn ifconfig
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:65536 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:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
veth1 Link encap:Ethernet HWaddr 3e:0a:b5:c6:f4:07
inet addr:10.0.0.254 Bcast:10.0.0.255 Mask:255.255.255.0
inet6 addr: fe80::3c0a:b5ff:fec6:f407/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1987 errors:0 dropped:0 overruns:0 frame:0
TX packets:75 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:146530 (146.5 KB) TX bytes:6799 (6.7 KB)
ip netns exec vpn ip route
default via 10.0.0.1 dev veth1
10.0.0.0/24 dev veth1 proto kernel scope link src 10.0.0.254
ip netns exec vpn route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 10.0.0.1 0.0.0.0 UG 0 0 0 veth1
10.0.0.0 * 255.255.255.0 U 0 0 0 veth1
我在运行 a 时执行了ping 10.0.0.254from ，然后从 tcpdump 输出文件中查找。您可以在此处查看整个 tcpdump（不长）10.0.0.4tcpdump -v -i br1 > file10.0.0.254http://pastebin.com/raw.php?i=Rs9dpw4V。
21:07:55.648413 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 10.0.0.254 tell 10.0.0.4, length 46
21:07:55.648448 ARP, Ethernet (len 6), IPv4 (len 4), Reply 10.0.0.254 is-at 3e:0a:b5:c6:f4:07 (oui Unknown), length 28
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 0, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 1, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 2, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 3, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 4, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 5, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 6, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 7, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 8, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 9, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 10, length 64
10.0.0.4 > 10.0.0.254: ICMP echo request, id 11630, seq 11, length 64
如果有任何缺失的信息，请告诉我。
编辑：
iptables -L -nv
Chain INPUT (policy ACCEPT 33M packets, 45G bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 17439 packets, 3112K bytes)
pkts bytes target prot opt in out source destination
2640K 3411M ACCEPT all -- br0 br1 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
2470K 464M ACCEPT all -- br1 br0 0.0.0.0/0 0.0.0.0/0
17439 3112K LOG all -- * * 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4
Chain OUTPUT (policy ACCEPT 21M packets, 35G bytes)
pkts bytes target prot opt in out source destination
iptables -t nat -L -nv
Chain PREROUTING (policy ACCEPT 280K packets, 30M bytes)
pkts bytes target prot opt in out source destination
Chain INPUT (policy ACCEPT 187K packets, 22M bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 198K packets, 13M bytes)
pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 58488 packets, 3569K bytes)
pkts bytes target prot opt in out source destination
222K 15M MASQUERADE all -- * br0 0.0.0.0/0 0.0.0.0/0
ip netns exec vpn arping -I veth1 -c 3 10.0.0.2
ARPING 10.0.0.2
60 bytes from 90:72:40:05:79:87 (10.0.0.2): index=0 time=1.001 sec
60 bytes from 90:72:40:05:79:87 (10.0.0.2): index=1 time=1.001 sec
60 bytes from 90:72:40:05:79:87 (10.0.0.2): index=2 time=1.001 sec
--- 10.0.0.2 statistics ---
arping -I br1 -c 3 10.0.0.254
ARPING 10.0.0.254
42 bytes from 3e:0a:b5:c6:f4:07 (10.0.0.254): index=0 time=1.001 sec
42 bytes from 3e:0a:b5:c6:f4:07 (10.0.0.254): index=1 time=1.001 sec
42 bytes from 3e:0a:b5:c6:f4:07 (10.0.0.254): index=2 time=1.001 sec
--- 10.0.0.254 statistics ---
3 packets transmitted, 3 packets received, 0% unanswered (0 extra)
答案1
我假设如果你这样做的话sudo iptables -L | grep policy它看起来会是这样的：
Chain INPUT (policy ACCEPT)
Chain FORWARD (policy DROP)
Chain OUTPUT (policy ACCEPT)
如果您只是这样做iptables --policy FORWARD ACCEPT。您的问题将得到解决。但是，如果服务器没有正确设置 iptables，则可能会很危险。因此，您可能需要参考这帮助您开始使用 iptables 的精彩指南。