[TOC]
### **目标**
模拟calico的跨主机容器网络通信，架构图如下：
### **步骤**
首先，根据上一篇文章的步骤配置好Pod与主机之间的通信。
然后，在104主机上执行以下命令：
```
$ modprobe -v ipip
$ ip link set tunl0 up
$ ip link set tunl0 mtu 1440
$ ip addr add 172.26.104.0/32 dev tunl0 broadcast 172.26.104.0
$ ip route add blackhole 172.26.104.0/24 proto bird
$ ip route add 172.26.105.0/24 via 192.168.2.105 dev tunl0 onlink
```
在105主机上执行以下命令：
```
$ modprobe -v ipip
$ ip link set tunl0 up
$ ip link set tunl0 mtu 1440
$ ip addr add 172.26.105.0/32 dev tunl0 broadcast 172.26.105.0
$ ip route add blackhole 172.26.105.0/24 proto bird
$ ip route add 172.26.104.0/24 via 192.168.2.104 dev tunl0 onlink
```
### **验证**
然后，我们查看主机的路由与网卡情况，104主机的如下：
```
$ ip route show
default via 192.168.2.2 dev ens33 proto static metric 100
blackhole 172.26.104.0/24 proto bird
172.26.104.1 dev cali0001 scope link
172.26.105.0/24 via 192.168.2.105 dev tunl0 onlink
192.168.2.0/24 dev ens33 proto kernel scope link src 192.168.2.104 metric 100
$ ip addr show
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
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:6e:a5:50 brd ff:ff:ff:ff:ff:ff
inet 192.168.2.104/24 brd 192.168.2.255 scope global noprefixroute ens33
valid_lft forever preferred_lft forever
4: cali0001@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1440 qdisc noqueue state UP group default qlen 1000
link/ether 72:15:53:e5:21:ae brd ff:ff:ff:ff:ff:ff link-netnsid 0
6: tunl0@NONE: <NOARP,UP,LOWER_UP> mtu 1440 qdisc noqueue state UNKNOWN group default qlen 1000
link/ipip 0.0.0.0 brd 0.0.0.0
inet 172.26.104.0/32 brd 172.26.104.0 scope global tunl0
valid_lft forever preferred_lft forever
```
然后，我们验证一下，从104的pod1 ping一下105的pod1，在104上执行
```
$ ip netns exec pod1 ping -c 1 172.26.105.1
PING 172.26.105.1 (172.26.105.1) 56(84) bytes of data.
64 bytes from 172.26.105.1: icmp_seq=1 ttl=62 time=3.21 ms
--- 172.26.105.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 3.217/3.217/3.217/0.000 ms
```
### **Q&A**
**Q：IPIP的大致原理是什么？**
A：
**Q：onlink和scope link有什么区别？**
A：
### **参考**
* http://www.asznl.com/post/83
* http://www.asznl.com/post/85
