同一个网段的两个 ip 无法互相 ping 通，可能是什么原因呢

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This topic created in 1390 days ago, the information mentioned may be changed or developed.

我有两台虚拟机

cdp: 192.168.64.5

ubuntu@cdp:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:8c:10:91 brd ff:ff:ff:ff:ff:ff inet 192.168.64.5/24 brd 192.168.64.255 scope global dynamic enp0s1 valid_lft 78881sec preferred_lft 78881sec inet6 fd96:bec8:dc5e:d1c1:5054:ff:fe8c:1091/64 scope global dynamic mngtmpaddr noprefixroute valid_lft 2591889sec preferred_lft 604689sec inet6 fe80::5054:ff:fe8c:1091/64 scope link valid_lft forever preferred_lft forever 3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default link/ether 02:42:ee:b9:4f:99 brd ff:ff:ff:ff:ff:ff inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0 valid_lft forever preferred_lft forever

ubuntu@cdp:~$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.64.1 0.0.0.0 UG 100 0 0 enp0s1 172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0 192.168.64.0 0.0.0.0 255.255.255.0 U 0 0 0 enp0s1 192.168.64.1 0.0.0.0 255.255.255.255 UH 100 0 0 enp0s1

lab: 192.168.64.6

ubuntu@lab:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:eb:e8:7b brd ff:ff:ff:ff:ff:ff inet 192.168.64.6/24 brd 192.168.64.255 scope global dynamic enp0s1 valid_lft 78849sec preferred_lft 78849sec inet6 fd96:bec8:dc5e:d1c1:5054:ff:feeb:e87b/64 scope global dynamic mngtmpaddr noprefixroute valid_lft 2591990sec preferred_lft 604790sec inet6 fe80::5054:ff:feeb:e87b/64 scope link valid_lft forever preferred_lft forever 3: dum0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 4a:c8:c0:64:e9:97 brd ff:ff:ff:ff:ff:ff inet 192.168.64.10/24 brd 192.168.64.255 scope global dum0 valid_lft forever preferred_lft forever inet6 fe80::48c8:c0ff:fe64:e997/64 scope link valid_lft forever preferred_lft forever

ubuntu@lab:~$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.64.1 0.0.0.0 UG 100 0 0 enp0s1 192.168.64.0 0.0.0.0 255.255.255.0 U 0 0 0 dum0 192.168.64.0 0.0.0.0 255.255.255.0 U 0 0 0 enp0s1 192.168.64.1 0.0.0.0 255.255.255.255 UH 100 0 0 enp0s1

然后我的主机 ip 是 192.168.64.1 。两台虚拟机是可以与主机互相连通的，但是两台虚拟机之间无法联通，出现 ping 超时的情况

而且，从两台虚拟机 ping 公网 ip ，比如百度，是可以通的。我用 arp 命令查看了一下，发现两台虚拟机都获取到了对方的 mac 地址

ubuntu@cdp:~$ arp -a _gateway (192.168.64.1) at f6:d4:88:98:8c:64 [ether] on enp0s1 ? (192.168.64.6) at 52:54:00:eb:e8:7b [ether] on enp0s1

而且，两台机器的 iptables 没有拦截的规则

Supplement 1 Jul 22, 2022

比较奇怪的是，我在某一天是可以互相 ping 通的。然后，最近几天发现就 ping 不通了

Supplement 2 Jul 22, 2022

按照 @riverskyfang 同学的方法，down 了一个虚拟网卡，就好了

13 replies 2022-07-23 04:28:39 +08:00

Phiiiil

Jul 22, 2022

cat /proc/sys/net/ipv4/icmp_echo_ignore_all

看看两台虚拟机是否关闭了 ping

pocketz

Jul 22, 2022

路由追踪什么结果？

DarkCat123

Jul 22, 2022

192.168.64.1 是一台什么机器？自己的 linux 服务器的话，是不是没有开转发。
`echo "1" > /proc/sys/net/ipv4/ip_forward`

NeoZephyr

Jul 22, 2022

@Phiiiil 并没有啊

```
ubuntu@lab:~$ cat /proc/sys/net/ipv4/icmp_echo_ignore_all
0
```

```
ubuntu@cdp:~$ cat /proc/sys/net/ipv4/icmp_echo_ignore_all
0
```

NeoZephyr

Jul 22, 2022

@pocketz 是 traceroute 吗

ubuntu@cdp:~$ traceroute 192.168.64.6
traceroute to 192.168.64.6 (192.168.64.6), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *

NeoZephyr

Jul 22, 2022

@DarkCat123

192.168.64.1 是我的 macOS 主机，192.168.64.5 和 192.168.64.6 是我主机上的两个虚拟机

riverskyfang

Jul 22, 2022

ifconfig dum0 down

nothingistrue

Jul 22, 2022

网关 192.168.64.1 ，是从你的宿主机上虚拟的网关，跟真是路由器网关可能会有区别，具体不能只看虚拟机上的网络配置，要看宿主机上的虚拟化配置。

NeoZephyr

Jul 22, 2022

@riverskyfang

wow! 可以了！这是为什么？因为 ip 冲突吗，我是为了测试，所以才自己加了一个虚拟网卡

ubuntu@lab:~$ sudo ip link set dum0 down
ubuntu@lab:~$
ubuntu@lab:~$
ubuntu@lab:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 52:54:00:eb:e8:7b brd ff:ff:ff:ff:ff:ff
inet 192.168.64.6/24 brd 192.168.64.255 scope global dynamic enp0s1
valid_lft 74516sec preferred_lft 74516sec
inet6 fd96:bec8:dc5e:d1c1:5054:ff:feeb:e87b/64 scope global dynamic mngtmpaddr noprefixroute
valid_lft 2591986sec preferred_lft 604786sec
inet6 fe80::5054:ff:feeb:e87b/64 scope link
valid_lft forever preferred_lft forever
3: dum0: <BROADCAST,NOARP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
link/ether 4a:c8:c0:64:e9:97 brd ff:ff:ff:ff:ff:ff
ubuntu@lab:~$
ubuntu@lab:~$
ubuntu@lab:~$
ubuntu@lab:~$ ping 192.168.64.5
PING 192.168.64.5 (192.168.64.5) 56(84) bytes of data.
64 bytes from 192.168.64.5: icmp_seq=1 ttl=64 time=4.84 ms
64 bytes from 192.168.64.5: icmp_seq=2 ttl=64 time=0.601 ms
^C
--- 192.168.64.5 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1022ms
rtt min/avg/max/mdev = 0.601/2.722/4.844/2.121 ms

riverskyfang

Jul 22, 2022

@NeoZephyr
lab 这台机器上的 192.168.64.0 子网包从 dum0 出去了，你已经贴了你的路由

NeoZephyr

Jul 22, 2022

@riverskyfang 嗯，是的

所以说 dum0 这个网卡有问题，没有工作，对吧

huobazi

Jul 22, 2022

目标主机可以禁 Ping 的

raysonx

Jul 23, 2022 via iPad

@NeoZephyr dummy interface 有点类似于 loopback ，你可以设置为 /32 掩码来做本地测试