| 1 | |
| 2 |
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| 3 | ===================
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| 4 | IPVLAN Driver HOWTO
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| 5 | ===================
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| 6 |
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| 7 | Initial Release:
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| 8 | Mahesh Bandewar <maheshb AT google.com>
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| 9 |
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| 10 | 1. Introduction:
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| 11 | ================
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| 12 | This is conceptually very similar to the macvlan driver with one major
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| 13 | exception of using L3 for mux-ing /demux-ing among slaves. This property makes
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| 14 | the master device share the L2 with its slave devices. I have developed this
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| 15 | driver in conjunction with network namespaces and not sure if there is use case
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| 16 | outside of it.
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| 17 |
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| 18 |
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| 19 | 2. Building and Installation:
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| 20 | =============================
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| 21 |
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| 22 | In order to build the driver, please select the config item CONFIG_IPVLAN.
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| 23 | The driver can be built into the kernel (CONFIG_IPVLAN=y) or as a module
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| 24 | (CONFIG_IPVLAN=m).
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| 25 |
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| 26 |
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| 27 | 3. Configuration:
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| 28 | =================
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| 29 |
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| 30 | There are no module parameters for this driver and it can be configured
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| 31 | using IProute2/ip utility.
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| 32 | ::
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| 33 |
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| 34 | ip link add link <master> name <slave> type ipvlan [ mode MODE ] [ FLAGS ]
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| 35 | where
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| 36 | MODE: l3 (default) | l3s | l2
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| 37 | FLAGS: bridge (default) | private | vepa
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| 38 |
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| 39 | e.g.
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| 40 |
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| 41 | (a) Following will create IPvlan link with eth0 as master in
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| 42 | L3 bridge mode::
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| 43 |
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| 44 | bash# ip link add link eth0 name ipvl0 type ipvlan
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| 45 | (b) This command will create IPvlan link in L2 bridge mode::
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| 46 |
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| 47 | bash# ip link add link eth0 name ipvl0 type ipvlan mode l2 bridge
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| 48 |
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| 49 | (c) This command will create an IPvlan device in L2 private mode::
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| 50 |
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| 51 | bash# ip link add link eth0 name ipvlan type ipvlan mode l2 private
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| 52 |
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| 53 | (d) This command will create an IPvlan device in L2 vepa mode::
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| 54 |
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| 55 | bash# ip link add link eth0 name ipvlan type ipvlan mode l2 vepa
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| 56 |
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| 57 |
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| 58 | 4. Operating modes:
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| 59 | ===================
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| 60 |
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| 61 | IPvlan has two modes of operation - L2 and L3. For a given master device,
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| 62 | you can select one of these two modes and all slaves on that master will
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| 63 | operate in the same (selected) mode. The RX mode is almost identical except
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| 64 | that in L3 mode the slaves won't receive any multicast / broadcast traffic.
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| 65 | L3 mode is more restrictive since routing is controlled from the other (mostly)
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| 66 | default namespace.
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| 67 |
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| 68 | 4.1 L2 mode:
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| 69 | ------------
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| 70 |
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| 71 | In this mode TX processing happens on the stack instance attached to the
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| 72 | slave device and packets are switched and queued to the master device to send
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| 73 | out. In this mode the slaves will RX/TX multicast and broadcast (if applicable)
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| 74 | as well.
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| 75 |
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| 76 | 4.2 L3 mode:
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| 77 | ------------
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| 78 |
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| 79 | In this mode TX processing up to L3 happens on the stack instance attached
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| 80 | to the slave device and packets are switched to the stack instance of the
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| 81 | master device for the L2 processing and routing from that instance will be
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| 82 | used before packets are queued on the outbound device. In this mode the slaves
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| 83 | will not receive nor can send multicast / broadcast traffic.
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| 84 |
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| 85 | 4.3 L3S mode:
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| 86 | -------------
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| 87 |
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| 88 | This is very similar to the L3 mode except that iptables (conn-tracking)
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| 89 | works in this mode and hence it is L3-symmetric (L3s). This will have slightly less
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| 90 | performance but that shouldn't matter since you are choosing this mode over plain-L3
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| 91 | mode to make conn-tracking work.
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| 92 |
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| 93 | 5. Mode flags:
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| 94 | ==============
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| 95 |
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| 96 | At this time following mode flags are available
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| 97 |
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| 98 | 5.1 bridge:
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| 99 | -----------
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| 100 | This is the default option. To configure the IPvlan port in this mode,
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| 101 | user can choose to either add this option on the command-line or don't specify
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| 102 | anything. This is the traditional mode where slaves can cross-talk among
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| 103 | themselves apart from talking through the master device.
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| 104 |
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| 105 | 5.2 private:
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| 106 | ------------
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| 107 | If this option is added to the command-line, the port is set in private
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| 108 | mode. i.e. port won't allow cross communication between slaves.
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| 109 |
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| 110 | 5.3 vepa:
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| 111 | ---------
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| 112 | If this is added to the command-line, the port is set in VEPA mode.
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| 113 | i.e. port will offload switching functionality to the external entity as
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| 114 | described in 802.1Qbg
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| 115 | Note: VEPA mode in IPvlan has limitations. IPvlan uses the mac-address of the
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| 116 | master-device, so the packets which are emitted in this mode for the adjacent
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| 117 | neighbor will have source and destination mac same. This will make the switch /
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| 118 | router send the redirect message.
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| 119 |
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| 120 | 6. What to choose (macvlan vs. ipvlan)?
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| 121 | =======================================
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| 122 |
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| 123 | These two devices are very similar in many regards and the specific use
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| 124 | case could very well define which device to choose. if one of the following
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| 125 | situations defines your use case then you can choose to use ipvlan:
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| 126 |
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| 127 |
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| 128 | (a) The Linux host that is connected to the external switch / router has
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| 129 | policy configured that allows only one mac per port.
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| 130 | (b) No of virtual devices created on a master exceed the mac capacity and
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| 131 | puts the NIC in promiscuous mode and degraded performance is a concern.
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| 132 | (c) If the slave device is to be put into the hostile / untrusted network
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| 133 | namespace where L2 on the slave could be changed / misused.
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| 134 |
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| 135 |
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| 136 | 6. Example configuration:
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| 137 | =========================
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| 138 |
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| 139 | ::
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| 140 |
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| 141 | +=============================================================+
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| 142 | | Host: host1 |
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| 143 | | |
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| 144 | | +----------------------+ +----------------------+ |
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| 145 | | | NS:ns0 | | NS:ns1 | |
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| 146 | | | | | | |
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| 147 | | | | | | |
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| 148 | | | ipvl0 | | ipvl1 | |
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| 149 | | +----------#-----------+ +-----------#----------+ |
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| 150 | | # # |
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| 151 | | ################################ |
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| 152 | | # eth0 |
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| 153 | +==============================#==============================+
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| 154 |
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| 155 |
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| 156 | (a) Create two network namespaces - ns0, ns1::
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| 157 |
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| 158 | ip netns add ns0
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| 159 | ip netns add ns1
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| 160 |
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| 161 | (b) Create two ipvlan slaves on eth0 (master device)::
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| 162 |
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| 163 | ip link add link eth0 ipvl0 type ipvlan mode l2
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| 164 | ip link add link eth0 ipvl1 type ipvlan mode l2
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| 165 |
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| 166 | (c) Assign slaves to the respective network namespaces::
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| 167 |
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| 168 | ip link set dev ipvl0 netns ns0
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| 169 | ip link set dev ipvl1 netns ns1
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| 170 |
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| 171 | (d) Now switch to the namespace (ns0 or ns1) to configure the slave devices
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| 172 |
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| 173 | - For ns0::
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| 174 |
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| 175 | (1) ip netns exec ns0 bash
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| 176 | (2) ip link set dev ipvl0 up
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| 177 | (3) ip link set dev lo up
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| 178 | (4) ip -4 addr add 127.0.0.1 dev lo
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| 179 | (5) ip -4 addr add $IPADDR dev ipvl0
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| 180 | (6) ip -4 route add default via $ROUTER dev ipvl0
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| 181 |
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| 182 | - For ns1::
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| 183 |
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| 184 | (1) ip netns exec ns1 bash
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| 185 | (2) ip link set dev ipvl1 up
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| 186 | (3) ip link set dev lo up
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| 187 | (4) ip -4 addr add 127.0.0.1 dev lo
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| 188 | (5) ip -4 addr add $IPADDR dev ipvl1
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| 189 | (6) ip -4 route add default via $ROUTER dev ipvl1
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