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05-Pre-requisite-Network-Namespace.md

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Pre-requisite Network Namespaces

In this section, we will take a look at Network Namespaces

Process Namespace

On the container

$ ps aux

On the host

$ ps aux

Network Namespace

$ route

$ arp

Create Network Namespace

$ ip netns add red

$ ip netns add blue
  • List the network namespace
$ ip netns

Exec in Network Namespace

  • List the interfaces on the host
$ ip link
  • Exec inside the network namespace
$ ip netns exec red ip link
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

$ ip netns exec blue ip link
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  • You can try with other options as well. Both works the same.
$ ip -n red link
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

ARP and Routing Table

On the host

$ arp
Address                  HWtype  HWaddress           Flags Mask            Iface
172.17.0.21              ether   02:42:ac:11:00:15   C                     ens3
172.17.0.55              ether   02:42:ac:11:00:37   C                     ens3

On the Network Namespace

$ ip netns exec red arp
Address                  HWtype  HWaddress           Flags Mask            Iface

$ ip netns exec blue arp
Address                  HWtype  HWaddress           Flags Mask            Iface

On the host

$ route

On the Network Namespace

$ ip netns exec red route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

$ ip netns exec blue route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

Virtual Cable

  • To create a virtual cable
$ ip link add veth-red type veth peer name veth-blue
  • To attach with the network namespaces
$ ip link set veth-red netns red

$ ip link set veth-blue netns blue
  • To add an IP address
$ ip -n red addr add 192.168.15.1/24 dev veth-red

$ ip -n blue addr add 192.168.15.2/24 dev veth-blue
  • To turn it up ns interfaces
$ ip -n red link set veth-red up

$ ip -n blue link set veth-blue up
  • Check the reachability
$ ip netns exec red ping 192.168.15.2
PING 192.168.15.2 (192.168.15.2) 56(84) bytes of data.
64 bytes from 192.168.15.2: icmp_seq=1 ttl=64 time=0.035 ms
64 bytes from 192.168.15.2: icmp_seq=2 ttl=64 time=0.046 ms

$ ip netns exec red arp
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.15.2             ether   da:a7:29:c4:5a:45   C                     veth-red

$ ip netns exec blue arp
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.15.1             ether   92:d1:52:38:c8:bc   C                     veth-blue
  • Delete the link.
$ ip -n red link del veth-red

On the host

# Not available
$ arp
Address                  HWtype  HWaddress           Flags Mask            Iface
172.16.0.72              ether   06:fe:61:1a:75:47   C                     ens3
172.17.0.68              ether   02:42:ac:11:00:44   C                     ens3
172.17.0.74              ether   02:42:ac:11:00:4a   C                     ens3
172.17.0.75              ether   02:42:ac:11:00:4b   C                     ens3

Linux Bridge

  • Create a network namespace
$ ip netns add red

$ ip netns add blue
  • To create a internal virtual bridge network, we add a new interface to the host
$ ip link add v-net-0 type bridge
  • Display in the host
$ ip link
8: v-net-0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether fa:fd:d4:9b:33:66 brd ff:ff:ff:ff:ff:ff
  • Currently it's down, so turn it up
$ ip link set dev v-net-0 up
  • To connect network namespace to the bridge. Creating a virtual cabel
$ ip link add veth-red type veth peer name veth-red-br

$ ip link add veth-blue type veth peer name veth-blue-br
  • Set with the network namespaces
$ ip link set veth-red netns red

$ ip link set veth-blue netns blue

$ ip link set veth-red-br master v-net-0

$ ip link set veth-blue-br master v-net-0
  • To add an IP address
$ ip -n red addr add 192.168.15.1/24 dev veth-red

$ ip -n blue addr add 192.168.15.2/24 dev veth-blue
  • To turn it up ns interfaces
$ ip -n red link set veth-red up

$ ip -n blue link set veth-blue up
  • To add an IP address
$ ip addr add 192.168.15.5/24 dev v-net-0
  • Turn it up added interfaces on the host
$ ip link set dev veth-red-br up
$ ip link set dev veth-blue-br up

On the host

$ ping 192.168.15.1

On the ns

$ ip netns exec blue ping 192.168.1.3
Connect: Network is unreachable

$ ip netns exec blue route

$ ip netns exec blue ip route add 192.168.1.0/24 via 192.168.15.5

# Check the IP Address of the host
$ ip a

$ ip netns exec blue ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.

$ iptables -t nat -A POSTROUTING -s 192.168.15.0/24 -j MASQUERADE

$ ip netns exec blue ping 192.168.1.3

$ ip netns exec blue ping 8.8.8.8

$ ip netns exec blue route

$ ip netns exec blue ip route add default via 192.168.15.5

$ ip netns exec blue ping 8.8.8.8
  • Adding port forwarding rule to the iptables
$ iptables -t nat -A PREROUTING --dport 80 --to-destination 192.168.15.2:80 -j DNAT

$ iptables -nvL -t nat