# DHCP snooping

### 1. Summary

This page is for configuring DHCP snooping.

### 2. Top page

This is the top page of DHCP Snooping.

#### 2.1. Display Binding Database

- Clicking the "Next" button will display a page where you can check the information of DHCP clients registered in thebinding database.

- If the system-wide DHCP snooping feature is disabled, the "Next" button cannot be pressed.

#### 2.2. System settings

- Displays the DHCP snooping settings in the system.

- The table items are explained below.

  - DHCP snooping function for the entire system

    - Displays whether or not DHCP snooping is enabled for the entire system.

  - MAC address verification

    - Displays whether or not to enable forwarding DHCP packets with Option 82 information via untrusted ports.

    - MAC address verification processcompares the source MAC address for packets received via an untrustedport with the client hardware address and discards corresponding DHCPpackets if the addresses do not match.

  - DHCP packets receiving rate limit

    - The setting for the number of DHCP packets that can be received per second is displayed.

  - Option 82 function

    - Shows whether Option 82 information is to be assigned, inspected, or deleted.

  - Forward packets with Option 82

    - Displays whether or not to enable forwarding of DHCP packets with Option 82 information on the Untrusted port.

  - Output to SYSLOG

    - Displays whether the reason for discarding DHCP packets is output to SYSLOG.

- Pressing the "Settings" button will bring up a page where you can configure the system settings.

#### 2.3. VLAN interface settings

- Displays the DHCP snooping function setting for each VLAN interface.

- The table items are explained below.

  - VLAN ID

    - VLAN ID is displayed.

  - DHCP snooping function

    - Displays whether the DHCP snooping function is enabled for the corresponding VLAN ID.

  - Remote ID

    - Displays the string assigned to the Option 82 remote ID.

  - Circuit ID

    - Displays information assigned to the Option 82 circuit ID.

- Press the "Setting" button to access a page where you can change the settings of the selected VLAN.

- Press the "Specify all" button to configure the settings for all VLAN interfaces with the check box selected.

- Press the "Return to defaults" button to initialize the settings for all VLAN interfaces with the check box selected.

#### 2.4. Interface settings

- Displays the DHCP snooping function setting for each interface.

- The table items are explained below.

  - Port

    - Displays the name of port for which the settings is to be changed.

  - Port type

    - Displays whether the corresponding port is trusted or untrusted.

  - Subscriber ID

    - Displays the string assigned to the Option 82 subscriber ID.

- Press the "Setting" button to display the page for configuring the selected interface.

- Press the "Specify all" button to configure the settings for all interfaces with the check box selected.

- Press the "Return to defaults" button to initialize the settings for all interfaces with the check box selected.

### 3. Display Binding Database page

This page displays information about DHCP clients registered in the binding database.

#### 3.1. Binding database

- Displays information on DHCP clients registered in the binding database.

- Up to 256 items will be displayed.

- You can search neighbor information from the "Search" box.

  - Press to execute the search.

  - Press to clear the search.

  - You can use regular expressions shown below in search keywords.

  - Lowercase and capital letters are treated the same for keywords.

    Syntax | Explanation
    --- | ---
    A | The character "A"
    ABC | The characters "ABC"
    [ABC] | One character, either "A", "B" or "C"
    [A-C] | One character between "A" and "C"
    [^ABC] | An arbitrary character that is neither "A", "B" or "C"
    . | An arbitrary character
    A+ | At least one "A" character
    A* | At least zero "A" characters
    A? | Zero or one "A" character
    ^A | A string that begins with "A"
    A$ | A string that ends with "A"
    ABC|DEF|GHI | "ABC", "DEF" or "GHI"
    A{2} | Two "A" characters (AA)
    A{2,} | Two or more "A" characters (AA, AAA, AAAA…​)
    A{2,3} | Two to three "A" characters (AA, AAA)
    \b | Word breaks, such as spaces
    \B | Any character besides \b
    \d | An arbitrary number (same as [0-9])
    \D | Any character besides numbers (same as [^0-9])
    \s | Single breaking character
    \S | Any single character besides \s
    \w | Alphanumeric characters including underlines (same as [A-Za-z0-9_])
    \W | Any character besides \w

  - Press to update information to the latest information.

  - The number of search results to display at one time can be selected by pressing "Display number" on the "Select" menu.

  - Press the sort switch to sort by each item.

    - With default settings, results are sorted in ascending order of the VLAN ID.

    - Press the sort switch again to toggle between ascending and descending order.

### 4. System settings page

This page is for configuring DHCP snooping in the system.
Enter the settings, and then press the "Confirm" button.
If there are no mistakes in the input content of the confirmation screen, press the "OK" button.

#### 4.1. System settings

- DHCP snooping function for the entire system

  - Selects whether to enable / disable the DHCP snooping function for the entire system.

- MAC address verification

  - Selects whether to enable / disable the MAC address verification on the Untrusted port.

- DHCP packets receiving rate limit

  - Enters the number of DHCP packets that can be received per second.

- Option 82 function

  - Selects whether to enable / disable Option 82 information assignment, inspection, and deletion.

- Forward packets with Option 82

  - Selects whether to enable / disable forwarding packets with Option 82 on the Untrusted port.

- Output to SYSLOG

  - Selects whether to enable / disable output to SYSLOG.

### 5. VLAN Interface settings page

This page is for configuring DHCP snooping on the VLAN interface.
You can also change the detailed settings by pressing the "Advanced settings" button.
Enter the settings, and then press the "Confirm" button.
If there are no mistakes in the input content of the confirmation screen, press the "OK" button.

#### 5.1. VLAN interface settings

- VLAN ID

  - Displays the VLAN ID for which the setting is to be changed.

- DHCP snooping function

  - Selects whether to enable/disable the DHCP snooping function for the corresponding VLAN ID.

- Remote ID

  - Enters the character string to be assigned to Option 82 remote ID.

  - Enter up to 63 single-byte alphanumeric characters/symbols, excluding the ? symbol.

- Circuit ID

  - Enters the character string to be assigned to Option 82 circuit ID.

  - Enter up to 63 single-byte alphanumeric characters/symbols, excluding the ? symbol.

### 6. Interface settings page

This page is for setting DHCP snooping on the interface.
You can also change the detailed settings by pressing the "Advanced settings" button.
Enter the settings, and then press the "Confirm" button.
If there are no mistakes in the input content of the confirmation screen, press the "OK" button.

#### 6.1. Interface settings

- Port

  - Displays the port name to configure the settings.

- DHCP snooping function

  - Port type

- Subscriber ID

  - Enters the character string to be assigned to Option 82 subscriber ID.

  - Enter up to 50 single-byte alphanumeric characters/symbols, excluding the ? symbol.

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