```bash ip netns add ns1 ip netns add ns2 ip link a v1 type veth peer name v1_r ip link a v2 type veth peer name v2_r ip a ip l s v1 netns ns1 ip l s v2 netns ns2 ip a ip netns exec ns1 ifconfig -a ip netns exec ns2 ifconfig -a ip netns exec ns1 ifconfig v1 up ip netns exec ns1 ip a a 10.10.10.2/24 dev v1 ip netns exec ns1 ifconfig ip netns exec ns1 ifconfig lo up ip netns exec ns1 ping -c 2 10.10.10.2 ip netns exec ns1 route -n ip netns exec ns1 route add -net 10.10.20.0/24 gw 10.10.10.1 ip netns exec ns1 route -n ip netns exec ns2 ip l s v2 up ip netns exec ns2 ip a a 10.10.20.2/24 dev v2 ip netns exec ns2 ifconfig ip netns exec ns2 ifconfig lo up ip netns exec ns2 ping -c 2 10.10.20.2 ip netns exec ns2 route -n ip netns exec ns2 route add -net 10.10.10.0/24 gw 10.10.20.1 ip netns exec ns2 route -n ip a a 10.10.10.1/24 dev v1_r ip a a 10.10.20.1/24 dev v2_r ip l s v1_r up ip l s v2_r up ip netns exec ns1 ping -c 2 10.10.20.1 ip netns exec ns1 ping -c 2 10.10.20.2 ip netns exec ns2 ping -c 2 10.10.10.1 ip netns exec ns2 ping -c 2 10.10.10.2 ip netns exec ns1 ip tunnel add tunl1 mode ipip local 10.10.10.2 remote 10.10.20.2 ip netns exec ns1 ip l s tunl1 up ip netns exec ns1 ip a a 10.10.100.10/24 peer 10.10.200.10/24 dev tunl1 ip netns exec ns1 ip a ip netns exec ns2 ip tunnel add tunl2 mode ipip local 10.10.20.2 remote 10.10.10.2 ip netns exec ns2 ip l s tunl2 up ip netns exec ns2 ip a a 10.10.200.10/24 peer 10.10.100.10/24 dev tunl2 ip netns exec ns2 ip a ```