Namespaces 08 - Connecting two network namespaces (ns1, ns2) - with two veth pairs and a standard Linux bridge

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 [1] NET namespace - Connecting two network namespaces (ns1, ns2) - with two veth pairs and
                     a standard Linux bridge
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     +------------------+                 +-------------------------------+                 +------------------+
     | ns1        veth1 |======cable======| veth1-br   bridge0   veth2-br |======cable======| veth2        ns2 |
     +------------------+                 +-------------------------------+                 +------------------+
       namespace "ns1"                           host system (bridge)                          namespace "ns2"

    The first  Ethernet cable (between namespace "ns1" and the Linux bridge "bridge0"): veth1====veth1-br
    The second Ethernet cable (between namespace "ns2" and the Linux bridge "bridge0"): veth2====veth2-br

    [1.1] - Remove the network namespaces "ns1" and "ns2" (if they exist).
    [1.2] - Create two network (NET) namespaces, "ns1" and "ns2".
    ----------------------------------------------------------------------------------------------------------------
    [1.1]# ip netns del ns1 &>/dev/null
    [1.1]# ip netns del ns2 &>/dev/null
    [1.2]# ip netns add ns1
    [1.2]# ip netns add ns2
    ----------------------------------------------------------------------------------------------------------------

    [1.3] - On the host system, create an Ethernet switch/bridge named "bridge0".
            Note: the package "bridge-utils" has to be installed; it is what administers the Linux bridge.
    [1.4] - Turn the Spanning Tree Protocol (STP) off on the Ethernet switch "bridge0".
    [1.5] - On the host system, bring the Ethernet switch "bridge0" up.
    ----------------------------------------------------------------------------------------------------------------
    [1.3]# brctl addbr bridge0
    [1.4]# brctl stp bridge0 off
    [1.5]# ip link set dev bridge0 up
    ----------------------------------------------------------------------------------------------------------------

    [1.6]TERM1 - In network namespace "ns1", exec the command "bash".
    [1.7]TERM2 - In network namespace "ns2", exec the command "bash".
    ----------------------------------------------------------------------------------------------------------------
    [1.6]TERM1# ip netns exec ns1 bash
    [1.7]TERM2# ip netns exec ns2 bash
    ----------------------------------------------------------------------------------------------------------------

    [1.8]  - Create a pair of virtual Ethernet devices, which stand for a network cable with two RJ45
             plugs, then put one end (veth1) into namespace "ns1" and the other end
             (veth1-br) into the Ethernet switch "bridge0".
    [1.9]  - Put the virtual Ethernet adapter "veth1" into network namespace "ns1".
    [1.10] - Connect the virtual Ethernet adapter "veth1-br" to the Ethernet switch "bridge0".

    [1.11] - Create a pair of virtual Ethernet devices, which stand for a network cable with two RJ45
             plugs, then put one end (veth2) into namespace "ns2" and the other end
             (veth2-br) into the Ethernet switch "bridge0".
    [1.12] - Put the virtual Ethernet adapter "veth2" into network namespace "ns2".
    [1.13] - Connect the virtual Ethernet adapter "veth2-br" to the Ethernet switch "bridge0".
    ----------------------------------------------------------------------------------------------------------------
    [1.8] # ip link add veth1 type veth peer name veth1-br
    [1.9] # ip link set veth1 netns ns1
    [1.10]# brctl addif bridge0 veth1-br

    [1.11]# ip link add veth2 type veth peer name veth2-br
    [1.12]# ip link set veth2 netns ns2
    [1.13]# brctl addif bridge0 veth2-br
    ----------------------------------------------------------------------------------------------------------------

    [1.14] - Bring the network adapter "veth1" up in namespace "ns1" and give it the address "10.0.0.1".
    [1.15] - Bring the network adapter/port "veth1-br" up on the standard Linux bridge "bridge0".

    [1.16] - Bring the network adapter "veth2" up in namespace "ns2" and give it the address "10.0.0.2".
    [1.17] - Bring the network adapter/port "veth2-br" up on the standard Linux bridge "bridge0".

    [1.18] - From network namespace "ns1", test that namespace "ns2" answers.
    [1.19] - From network namespace "ns2", test that namespace "ns1" answers.
    ----------------------------------------------------------------------------------------------------------------
    [1.14]# ip netns exec ns1 ifconfig veth1 10.0.0.1/24 up
    [1.15]# ip link set dev veth1-br up

    [1.16]# ip netns exec ns2 ifconfig veth2 10.0.0.2/24 up
    [1.17]# ip link set dev veth2-br up

    [1.18]# ip netns exec ns1 ping 10.0.0.2
    [1.19]# ip netns exec ns2 ping 10.0.0.1
    ----------------------------------------------------------------------------------------------------------------

$ # ip link add bridge0 type bridge stp_state 0
$ # ip link set bridge0 up
$ # ip link set veth1-br master bridge0
$ # ip link set veth2-br master bridge0
$ # bridge link show