> For the complete documentation index, see [llms.txt](https://docs.console.zenlayer.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.console.zenlayer.com/welcome/elastic-compute/get-started/manage-instances/bind-an-elastic-ipv4-address.md).

# Bind an Elastic IPv4 Address

You can bind up to 4 elastic IPv4 addresses to a private IPv4.

## Procedures

1. Click the instance name to go to instance **Details** > **Information** > **Network interface**.
2. Select the private IPv4 you want to bind elastic IPv4 and go to **Actions** > **Bind Elastic IPv4**.

   <figure><img src="/files/wjBu0vB9lmSaflwjb85S" alt=""><figcaption></figcaption></figure>
3. Select a desired elastic IPv4 and click **Confirm** to bind. If no desired elastic IPv4, click **New Elastic IPv4** to create a new IPv4.\
   See [**Create an Elastic IPv4**](/welcome/elastic-compute/get-started/manage-networking/create-an-elastic-ipv4.md) for detailed steps.

   <div align="left"><figure><img src="/files/csRjhiQY0s0NsH7cOd3f" alt="" width="444"><figcaption></figcaption></figure></div>

{% hint style="info" %} <mark style="color:blue;">**Note**</mark>

<mark style="color:blue;">You can also go to</mark> <mark style="color:blue;">**Elastic IPv4**</mark> <mark style="color:blue;">></mark> <mark style="color:blue;">**Actions**</mark> <mark style="color:blue;">></mark> <mark style="color:blue;">**Bind Private IPv4**</mark> <mark style="color:blue;">to bind the elastic IPv4.</mark>

<img src="/files/0N4G8OGcbhhJj7VO69DD" alt="" data-size="original">
{% endhint %}

## Bypass Mode Configuration Guide

### 1. Scope and Prerequisites

#### 1.1 Applicable Scenarios

* **Single network interface (NIC) only**
* Supports multiple IPs (up to 254)
* All IPs must be in **Bypass mode**

#### 1.2 Supported Operating Systems

* Ubuntu: 20.04 / 22.04 / 24.04
* Debian: 10 / 11 / 12
* CentOS: 7 / 9
* Rocky Linux: 8.10 / 9.6

#### 1.3 Important Notes

* **A reboot is required after running the script**, otherwise the configuration will not take effect
* Mixed modes are not supported (Bypass Mode + NAT Mode)

### 2. Operation Steps

{% tabs %}
{% tab title="Console" %}

1. Create Command:

Path:

> Console → Orchestration Service → Commands → Create Commands

copy and add the following script and create command.

{% code expandable="true" %}

```shellscript
#!/bin/sh -e
# Task Description:
#   Used for initializing configuration in single NIC EIP full Bypass mode scenarios.
#   Supports from 1 public IP up to 254 public IPs.
#   Execute this task after external resource environment is ready.
#   Adapted for ubuntu20.04, 22.04, 24.04, debian10, 11, 12, centos7, centos9, rocky9.6, rocky8.10 (10 systems)

# ===== Global Variable Definitions =====
TASK_NAME=single_nic_bypass_init

META_CURL="curl -sf"
META_URL="http://169.254.169.254/latest/meta-data/network/interfaces/macs"

NIC_NAME=eth0
PRI_GW4=
PRI_IP4=
PRI_PREFIX=

SYSTEM=

DEFAULT_PUB_EIP4=
ALL_PUB_EIP4s=

NAME_SERVER1=8.8.8.8
NAME_SERVER2=1.1.1.1
# =======================

CheckSupportedOS() {
    if [ ! -f /etc/os-release ]; then
        echo "Error: Unsupported system: /etc/os-release not found"
        exit 1
    fi

    . /etc/os-release

    if [ "$ID" = "ubuntu" ]; then
        if [ "$VERSION_ID" = "20.04" ] || [ "$VERSION_ID" = "22.04" ] || [ "$VERSION_ID" = "24.04" ]; then
            echo "Supported OS: Ubuntu $VERSION_ID"
            SYSTEM=ubuntu
            return 0
        else
            echo "Error: Unsupported Ubuntu version: $VERSION_ID"
            exit 1
        fi
    elif [ "$ID" = "debian" ]; then
        if [ "$VERSION_ID" = "11" ] || [ "$VERSION_ID" = "10" ] || [ "$VERSION_ID" = "12" ]; then
            echo "Supported OS: Debian $VERSION_ID"
            SYSTEM=debian
            return 0
        else
            echo "Unsupported Debian version: $VERSION_ID"
            exit 1
        fi
    elif [ "$ID" = "centos" ] || [ "$ID" = "rhel" ]; then
        if [ "$VERSION_ID" = "7" ] && [ -f /etc/centos-release ]; then
            echo "Supported OS: CentOS $VERSION_ID"
            SYSTEM=centos
            return 0
        elif [ "$VERSION_ID" = "9" ] && [ -f /etc/centos-release ]; then
            echo "Supported OS: CentOS $VERSION_ID"
            SYSTEM=centos
            return 0
        else
            echo "Unsupported CentOS/RHEL version: $VERSION_ID"
            exit 1
        fi
    elif [ "$ID" = "rocky" ]; then
        if [ "$VERSION_ID" = "9.6" ] || [ "$VERSION_ID" = "8.10" ]; then
            echo "Supported OS: rocky $VERSION_ID"
            SYSTEM=rocky
            return 0
        else
            echo "Unsupported rocky version: $VERSION_ID"
            exit 1
        fi
    else
        echo "Unsupported OS: $ID $VERSION_ID"
        exit 1
    fi
}

ConfigUbuntuNetwork() {
    cat > /etc/netplan/50-cloud-init.yaml << EOF
network:
    version: 2
    ethernets:
        eth0:
            addresses:
                - ${PRI_IP4}/${PRI_PREFIX}
EOF

    for EIP in $ALL_PUB_EIP4s; do
        echo "                - ${EIP}/32" >> /etc/netplan/50-cloud-init.yaml
    done

    cat >> /etc/netplan/50-cloud-init.yaml << EOF
            nameservers:
                addresses:
                - ${NAME_SERVER1}
                - ${NAME_SERVER2}
EOF
    # Default route
    cat >> /etc/netplan/50-cloud-init.yaml << EOF
            routes:
                - to: default
                  via: ${PRI_GW4}
                  from: ${DEFAULT_PUB_EIP4}
EOF
}

ConfigCentOSNetwork() {
    rm -f /etc/sysconfig/network-scripts/ifcfg-eth0*
    cat << EOF > /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
IPADDR=${PRI_IP4}
PREFIX=${PRI_PREFIX}
EOF

index=0

    for EIP in $ALL_PUB_EIP4s; do
        cat << EOF > /etc/sysconfig/network-scripts/ifcfg-eth0:$index
DEVICE=eth0:$index
BOOTPROTO=static
ONBOOT=yes
IPADDR=${EIP}
PREFIX=32
EOF
        index=$((index+1))
    done

    # Default route
    cat << EOF > /etc/sysconfig/network-scripts/route-eth0
default via ${PRI_GW4} dev eth0 src ${DEFAULT_PUB_EIP4}
EOF
    # Disable DHCP on eth2
    cat << EOF > /etc/sysconfig/network-scripts/ifcfg-eth2
DEVICE=eth2
BOOTPROTO=none
ONBOOT=yes
EOF
}

ConfigDebianNetwork() {
    cat > /etc/network/interfaces.d/50-cloud-init << EOF

auto lo
iface lo inet loopback
    dns-nameservers ${NAME_SERVER1} ${NAME_SERVER2}

auto eth0
iface eth0 inet static
    address ${PRI_IP4}/${PRI_PREFIX}

auto eth0:0
iface eth0:0 inet static
    address ${DEFAULT_PUB_EIP4}/32
    up ip route add default via ${PRI_GW4} dev eth0 src ${DEFAULT_PUB_EIP4}
    down ip route del default via ${PRI_GW4} dev eth0 src ${DEFAULT_PUB_EIP4}
EOF

    index=1

    for EIP in $ALL_PUB_EIP4s; do
        if [ "$EIP" = "$DEFAULT_PUB_EIP4" ]; then
            continue
        fi
        cat >> /etc/network/interfaces.d/50-cloud-init << EOF

auto eth0:$index
iface eth0:$index inet static
    address ${EIP}/32
EOF
       index=$((index+1))
    done
}

FetchMetaData() {
    pri_macs=$($META_CURL $META_URL/ | sed 's/\///g')

    nic_count=$(echo "$pri_macs" | wc -w | tr -d ' ')
    if [ "$nic_count" -ne 1 ]; then
        echo "[ERR] Expected exactly one nic, got $nic_count: $pri_macs" >&2
        exit 4
    fi

    PRI_IP4=$($META_CURL $META_URL/$pri_macs/primary-ip-address)
    pri_subnet_cidr=$($META_CURL $META_URL/$pri_macs/subnet-cidr-block)
    PRI_PREFIX=$(echo "$pri_subnet_cidr" | cut -d'/' -f2)
    PRI_GW4=$($META_CURL $META_URL/$pri_macs/gateway)
    DEFAULT_PUB_EIP4=$($META_CURL $META_URL/$pri_macs/public-ipv4)
    ALL_PUB_EIP4s=$($META_CURL $META_URL/$pri_macs/public-ipv4s | sed 's/\[//;s/\]//;s/"//g;s/,/ /g')

    if [ -z "$pri_macs" ] || [ -z "$PRI_IP4" ] || [ -z "$pri_subnet_cidr" ] || [ -z "$PRI_PREFIX" ] || [ -z "$PRI_GW4" ] || [ -z "$DEFAULT_PUB_EIP4" ] || [ -z "$ALL_PUB_EIP4s" ]; then
        echo "[ERR] Missing metadata, check EC2 metadata service." >&2
        exit 3
    fi

    echo "  Private MacAddr:     $pri_macs"
    echo "  Private IPv4:        $PRI_IP4"
    echo "  Private Prefix:      $PRI_PREFIX"
    echo "  Private GWv4:        $PRI_GW4"
    echo "  ALl Public IPv4:     $ALL_PUB_EIP4s"
    echo "  Default Public IPv4: $DEFAULT_PUB_EIP4"
}

ConfigNetwork() {
    # Disable RPF (Reverse Path Filtering)
    if ! grep -q "net.ipv4.conf.all.rp_filter=0" /etc/sysctl.conf; then
        echo "net.ipv4.conf.all.rp_filter=0" | tee -a /etc/sysctl.conf > /dev/null
        sysctl -p /etc/sysctl.conf
    fi

    # Disable cloud-init network configuration
    echo "network: {config: disabled}" > /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg

    if [ "$SYSTEM" = "ubuntu" ]; then
        ConfigUbuntuNetwork
    elif [ "$SYSTEM" = "centos" ]; then
        ConfigCentOSNetwork
    elif [ "$SYSTEM" = "debian" ]; then
        if [ "$VERSION_ID" = "11" ] || [ "$VERSION_ID" = "10" ]; then
            ConfigDebianNetwork
        elif [ "$VERSION_ID" = "12" ]; then
            ConfigUbuntuNetwork
        else
            echo "Unsupported Debian version: $VERSION_ID"
            exit 1
        fi
    elif [ "$SYSTEM" = "rocky" ]; then
        ConfigCentOSNetwork
    else
        echo "Unsupported OS for network config: $SYSTEM"
        exit 1
    fi
}

echo "1. Check OS..."
CheckSupportedOS

echo

echo "2. FetchMetaData..."
FetchMetaData

echo

echo "3. Configuring networks..."
ConfigNetwork

echo

echo
echo "Done."

sync
```

{% endcode %}

2. Run Command:

Path:

> Console → Elastic Compute → Elastic Compute Instance List → Actions → Operations → Run command → Select the command→ Confirm

Run the created command.

3. Reboot the Instance

After execution, **you must manually reboot the instance**.

4. Add Additional IPs (Optional)

To attach more IPs, repeat:

* Bind IP
* Run command
* Reboot instance
  {% endtab %}

{% tab title="API" %}

1. Create Compute Instance

Create an instance following the standard process.

2. Create and Bind EIP

* Create an Elastic IP
* Bind it to the instance in **Bypass mode**

3. Run Command via API

Call the API to run the command:

API Documentation:\
<https://docs.console.zenlayer.com/api-reference/security/zos/command/createcommand>

Use the script provided following.

{% code expandable="true" %}

```shellscript
#!/bin/sh -e
# Task Description:
#   Used for initializing configuration in single NIC EIP full Bypass mode scenarios.
#   Supports from 1 public IP up to 254 public IPs.
#   Execute this task after external resource environment is ready.
#   Adapted for ubuntu20.04, 22.04, 24.04, debian10, 11, 12, centos7, centos9, rocky9.6, rocky8.10 (10 systems)

# ===== Global Variable Definitions =====
TASK_NAME=single_nic_bypass_init

META_CURL="curl -sf"
META_URL="http://169.254.169.254/latest/meta-data/network/interfaces/macs"

NIC_NAME=eth0
PRI_GW4=
PRI_IP4=
PRI_PREFIX=

SYSTEM=

DEFAULT_PUB_EIP4=
ALL_PUB_EIP4s=

NAME_SERVER1=8.8.8.8
NAME_SERVER2=1.1.1.1
# =======================

CheckSupportedOS() {
    if [ ! -f /etc/os-release ]; then
        echo "Error: Unsupported system: /etc/os-release not found"
        exit 1
    fi

    . /etc/os-release

    if [ "$ID" = "ubuntu" ]; then
        if [ "$VERSION_ID" = "20.04" ] || [ "$VERSION_ID" = "22.04" ] || [ "$VERSION_ID" = "24.04" ]; then
            echo "Supported OS: Ubuntu $VERSION_ID"
            SYSTEM=ubuntu
            return 0
        else
            echo "Error: Unsupported Ubuntu version: $VERSION_ID"
            exit 1
        fi
    elif [ "$ID" = "debian" ]; then
        if [ "$VERSION_ID" = "11" ] || [ "$VERSION_ID" = "10" ] || [ "$VERSION_ID" = "12" ]; then
            echo "Supported OS: Debian $VERSION_ID"
            SYSTEM=debian
            return 0
        else
            echo "Unsupported Debian version: $VERSION_ID"
            exit 1
        fi
    elif [ "$ID" = "centos" ] || [ "$ID" = "rhel" ]; then
        if [ "$VERSION_ID" = "7" ] && [ -f /etc/centos-release ]; then
            echo "Supported OS: CentOS $VERSION_ID"
            SYSTEM=centos
            return 0
        elif [ "$VERSION_ID" = "9" ] && [ -f /etc/centos-release ]; then
            echo "Supported OS: CentOS $VERSION_ID"
            SYSTEM=centos
            return 0
        else
            echo "Unsupported CentOS/RHEL version: $VERSION_ID"
            exit 1
        fi
    elif [ "$ID" = "rocky" ]; then
        if [ "$VERSION_ID" = "9.6" ] || [ "$VERSION_ID" = "8.10" ]; then
            echo "Supported OS: rocky $VERSION_ID"
            SYSTEM=rocky
            return 0
        else
            echo "Unsupported rocky version: $VERSION_ID"
            exit 1
        fi
    else
        echo "Unsupported OS: $ID $VERSION_ID"
        exit 1
    fi
}

ConfigUbuntuNetwork() {
    cat > /etc/netplan/50-cloud-init.yaml << EOF
network:
    version: 2
    ethernets:
        eth0:
            addresses:
                - ${PRI_IP4}/${PRI_PREFIX}
EOF

    for EIP in $ALL_PUB_EIP4s; do
        echo "                - ${EIP}/32" >> /etc/netplan/50-cloud-init.yaml
    done

    cat >> /etc/netplan/50-cloud-init.yaml << EOF
            nameservers:
                addresses:
                - ${NAME_SERVER1}
                - ${NAME_SERVER2}
EOF
    # Default route
    cat >> /etc/netplan/50-cloud-init.yaml << EOF
            routes:
                - to: default
                  via: ${PRI_GW4}
                  from: ${DEFAULT_PUB_EIP4}
EOF
}

ConfigCentOSNetwork() {
    rm -f /etc/sysconfig/network-scripts/ifcfg-eth0*
    cat << EOF > /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
IPADDR=${PRI_IP4}
PREFIX=${PRI_PREFIX}
EOF

index=0

    for EIP in $ALL_PUB_EIP4s; do
        cat << EOF > /etc/sysconfig/network-scripts/ifcfg-eth0:$index
DEVICE=eth0:$index
BOOTPROTO=static
ONBOOT=yes
IPADDR=${EIP}
PREFIX=32
EOF
        index=$((index+1))
    done

    # Default route
    cat << EOF > /etc/sysconfig/network-scripts/route-eth0
default via ${PRI_GW4} dev eth0 src ${DEFAULT_PUB_EIP4}
EOF
    # Disable DHCP on eth2
    cat << EOF > /etc/sysconfig/network-scripts/ifcfg-eth2
DEVICE=eth2
BOOTPROTO=none
ONBOOT=yes
EOF
}

ConfigDebianNetwork() {
    cat > /etc/network/interfaces.d/50-cloud-init << EOF

auto lo
iface lo inet loopback
    dns-nameservers ${NAME_SERVER1} ${NAME_SERVER2}

auto eth0
iface eth0 inet static
    address ${PRI_IP4}/${PRI_PREFIX}

auto eth0:0
iface eth0:0 inet static
    address ${DEFAULT_PUB_EIP4}/32
    up ip route add default via ${PRI_GW4} dev eth0 src ${DEFAULT_PUB_EIP4}
    down ip route del default via ${PRI_GW4} dev eth0 src ${DEFAULT_PUB_EIP4}
EOF

    index=1

    for EIP in $ALL_PUB_EIP4s; do
        if [ "$EIP" = "$DEFAULT_PUB_EIP4" ]; then
            continue
        fi
        cat >> /etc/network/interfaces.d/50-cloud-init << EOF

auto eth0:$index
iface eth0:$index inet static
    address ${EIP}/32
EOF
       index=$((index+1))
    done
}

FetchMetaData() {
    pri_macs=$($META_CURL $META_URL/ | sed 's/\///g')

    nic_count=$(echo "$pri_macs" | wc -w | tr -d ' ')
    if [ "$nic_count" -ne 1 ]; then
        echo "[ERR] Expected exactly one nic, got $nic_count: $pri_macs" >&2
        exit 4
    fi

    PRI_IP4=$($META_CURL $META_URL/$pri_macs/primary-ip-address)
    pri_subnet_cidr=$($META_CURL $META_URL/$pri_macs/subnet-cidr-block)
    PRI_PREFIX=$(echo "$pri_subnet_cidr" | cut -d'/' -f2)
    PRI_GW4=$($META_CURL $META_URL/$pri_macs/gateway)
    DEFAULT_PUB_EIP4=$($META_CURL $META_URL/$pri_macs/public-ipv4)
    ALL_PUB_EIP4s=$($META_CURL $META_URL/$pri_macs/public-ipv4s | sed 's/\[//;s/\]//;s/"//g;s/,/ /g')

    if [ -z "$pri_macs" ] || [ -z "$PRI_IP4" ] || [ -z "$pri_subnet_cidr" ] || [ -z "$PRI_PREFIX" ] || [ -z "$PRI_GW4" ] || [ -z "$DEFAULT_PUB_EIP4" ] || [ -z "$ALL_PUB_EIP4s" ]; then
        echo "[ERR] Missing metadata, check EC2 metadata service." >&2
        exit 3
    fi

    echo "  Private MacAddr:     $pri_macs"
    echo "  Private IPv4:        $PRI_IP4"
    echo "  Private Prefix:      $PRI_PREFIX"
    echo "  Private GWv4:        $PRI_GW4"
    echo "  ALl Public IPv4:     $ALL_PUB_EIP4s"
    echo "  Default Public IPv4: $DEFAULT_PUB_EIP4"
}

ConfigNetwork() {
    # Disable RPF (Reverse Path Filtering)
    if ! grep -q "net.ipv4.conf.all.rp_filter=0" /etc/sysctl.conf; then
        echo "net.ipv4.conf.all.rp_filter=0" | tee -a /etc/sysctl.conf > /dev/null
        sysctl -p /etc/sysctl.conf
    fi

    # Disable cloud-init network configuration
    echo "network: {config: disabled}" > /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg

    if [ "$SYSTEM" = "ubuntu" ]; then
        ConfigUbuntuNetwork
    elif [ "$SYSTEM" = "centos" ]; then
        ConfigCentOSNetwork
    elif [ "$SYSTEM" = "debian" ]; then
        if [ "$VERSION_ID" = "11" ] || [ "$VERSION_ID" = "10" ]; then
            ConfigDebianNetwork
        elif [ "$VERSION_ID" = "12" ]; then
            ConfigUbuntuNetwork
        else
            echo "Unsupported Debian version: $VERSION_ID"
            exit 1
        fi
    elif [ "$SYSTEM" = "rocky" ]; then
        ConfigCentOSNetwork
    else
        echo "Unsupported OS for network config: $SYSTEM"
        exit 1
    fi
}

echo "1. Check OS..."
CheckSupportedOS

echo

echo "2. FetchMetaData..."
FetchMetaData

echo

echo "3. Configuring networks..."
ConfigNetwork

echo

echo
echo "Done."

sync
```

{% endcode %}

4. Reboot the Instance

Call the API to reboot the instance to apply the configuration.

5. Add Additional IPs (Optional)

To attach more IPs, repeat:

* Bind IP
* Run command
* Reboot instance
  {% endtab %}
  {% endtabs %}

### 3. Troubleshooting

#### 3.1 Configuration Not Taking Effect

* Cause: Instance not rebooted
* Solution: Reboot the instance

#### 3.2 Configuration Failure

* Ensure all IPs are in Bypass mode
* Verify the OS is within the supported list