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nguns
Asked: 2020-04-03 04:27:39 +0800 CST

GRE 隧道之间的 Centos7 上未转发数据包

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如图所示，我已经在 centos 机器和各个 centos 机器上的相应路由表之间配置了 GRE 隧道：

I dont have enough reputation to post images

Router1--------gre1---------Transit-Router---------gre2--------Router2

10.2.32.0/24--Router1--10.0.0.1---gre1---10.0.0.2--Transit-Router--11.0.0.2---gre2--11.0.0.1--Router2--10.4.32.0 /24

我能够从 Router-1 ping 到 gre1 隧道的另一端：

worker]# ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=1.43 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.472 ms
64 bytes from 10.0.0.2: icmp_seq=3 ttl=64 time=0.291 ms
64 bytes from 10.0.0.2: icmp_seq=4 ttl=64 time=0.319 ms

流量通过 GRE 隧道到达 Transit Router（由 tcpdump proto gre 验证）

从 Router-2 ping 到 gre2 隧道另一端：

worker]# ping 11.0.0.2
PING 11.0.0.2 (11.0.0.2) 56(84) bytes of data.
64 bytes from 11.0.0.2: icmp_seq=1 ttl=64 time=1.10 ms
64 bytes from 11.0.0.2: icmp_seq=2 ttl=64 time=0.392 ms
64 bytes from 11.0.0.2: icmp_seq=3 ttl=64 time=0.369 ms
64 bytes from 11.0.0.2: icmp_seq=4 ttl=64 time=0.258 ms

此流量也在隧道上流动

在中转路由器上，我可以在添加路由条目后 ping 路由器 1 和路由器 2 的私有地址： 中转路由器：

[root@vmc-centos conf]# ping 10.2.32.1
PING 10.2.32.1 (10.2.32.1) 56(84) bytes of data.
64 bytes from 10.2.32.1: icmp_seq=1 ttl=64 time=0.589 ms
64 bytes from 10.2.32.1: icmp_seq=2 ttl=64 time=0.380 ms
64 bytes from 10.2.32.1: icmp_seq=3 ttl=64 time=0.383 ms

路由器 1：

worker]# tcpdump -i any proto gre -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
04:54:36.684864 IP 10.206.83.3 > 10.206.90.103: GREv0, length 88: IP 10.0.0.2 > 10.2.32.1: ICMP echo request, id 20445, seq 34, length 64
04:54:36.684951 IP 10.206.90.103 > 10.206.83.3: GREv0, length 88: IP 10.2.32.1 > 10.0.0.2: ICMP echo reply, id 20445, seq 34, length 64
04:54:37.684776 IP 10.206.83.3 > 10.206.90.103: GREv0, length 88: IP 10.0.0.2 > 10.2.32.1: ICMP echo request, id 20445, seq 35, length 64

中转路由器：

[root@vmc-centos conf]# ping 10.4.32.1
PING 10.4.32.1 (10.4.32.1) 56(84) bytes of data.
64 bytes from 10.4.32.1: icmp_seq=1 ttl=64 time=0.553 ms
64 bytes from 10.4.32.1: icmp_seq=2 ttl=64 time=0.325 ms
64 bytes from 10.4.32.1: icmp_seq=3 ttl=64 time=0.354 ms

路由器 2：

worker]# sudo tcpdump -i any proto gre -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
04:56:57.549823 IP 10.206.83.3 > 10.206.86.199: GREv0, length 88: IP 11.0.0.2 > 10.4.32.1: ICMP echo request, id 20690, seq 24, length 64
04:56:57.549896 IP 10.206.86.199 > 10.206.83.3: GREv0, length 88: IP 10.4.32.1 > 11.0.0.2: ICMP echo reply, id 20690, seq 24, length 64

但是现在当我尝试从路由器 1 到达路由器 2（10.4.32.1）的专用网络时，数据包到达中转路由器但没有从那里转发到路由器 2：路由器 1：

worker]# ping 10.4.32.1
PING 10.4.32.1 (10.4.32.1) 56(84) bytes of data.

中转路由器：

[root@vmc-centos conf]# tcpdump -i any proto gre -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
04:59:06.382024 IP 10.206.90.103 > 10.206.83.3: GREv0, length 88: IP 10.0.0.1 > 10.4.32.1: ICMP echo request, id 36131, seq 40, length 64
04:59:07.382007 IP 10.206.90.103 > 10.206.83.3: GREv0, length 88: IP 10.0.0.1 > 10.4.32.1: ICMP echo request, id 36131, seq 41, length 64

路由器 2：

[root@wdc-10-206-86-199 worker]# sudo tcpdump -i any proto gre -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes

在所有机器上启用路由转发：

[root@vmc-centos conf]# sudo sysctl -p
net.ipv4.ip_forward = 1

中转路由器上的 iptables：

[root@vmc-centos ~]# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     gre  --  anywhere             anywhere            
ACCEPT     gre  --  anywhere             anywhere            

Chain FORWARD (policy DROP)
target     prot opt source               destination         
DOCKER-USER  all  --  anywhere             anywhere            
DOCKER-ISOLATION-STAGE-1  all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
DOCKER     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere            

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     gre  --  anywhere             anywhere            

Chain DOCKER (1 references)
target     prot opt source               destination         

Chain DOCKER-ISOLATION-STAGE-1 (1 references)
target     prot opt source               destination         
DOCKER-ISOLATION-STAGE-2  all  --  anywhere             anywhere            
RETURN     all  --  anywhere             anywhere            

Chain DOCKER-ISOLATION-STAGE-2 (1 references)
target     prot opt source               destination         
DROP       all  --  anywhere             anywhere            
RETURN     all  --  anywhere             anywhere            

Chain DOCKER-USER (1 references)
target     prot opt source               destination         
RETURN     all  --  anywhere             anywhere

注意：我之前已经尝试过，数据包正在到达另一个专用网络。现在我尝试另一种设置，我缺少一些配置。

linux centos networking gre

1 个回答

  1. Best Answer

    Docker 守护进程似乎正在转发机器上运行。默认情况下，为了隔离不同网桥和宿主机上的容器，Docker 会在 iptables 中的转发链上安装一个默认的 DROP 策略。Docker 守护程序中有一个设置不这样做。在 .iptables 中将 iptables 设置为 false /etc/docker/daemon.json。请参阅Docker 和 iptables

    如果您将默认策略更改为接受，那将起作用。

    iptables --policy FORWARD ACCEPT

    但是，当您（或 docker 的软件包升级，或重新启动）重新启动 Docker 守护程序时，如果您没有更改 docker 守护程序的设置，默认策略将再次更改为 DROP。

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