---
title: "About Relay Agent Filters"
canonical: "https://docs.infoblox.com/space/nios85/35848923/About%20Relay%20Agent%20Filters"
format: markdown
---
The NIOS appliance can filter an address request by the circuit ID and remote ID of a requesting host. The filter instructs the appliance either to grant or deny an address request if the requesting host matches the filter. For information about the DHCP relay agent option, see *<span style="color: #0000ff">[About](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[the](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[DHCP](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[Relay](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[Agent](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[Option](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[(Option](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)*<span style="color: #0000ff">[82)](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35946818/About+IPv4+DHCP+Options#AboutIPv4DHCPOptions-bookmark2275)</span>*.  
Option 82 assists the agent in forwarding address assignments across the proper circuit. When a relay agent receives a DHCPDISCOVER message, it can add one or two agent IDs (circuit ID or remote ID) in the DHCP option 82 suboption fields to the message, as illustrated in <span style="color: #0000ff">[*Figure 31.5*](https://infoblox-docs.atlassian.net/wiki/spaces/nios85draft/pages/26477992)</span>. If the agent ID strings match those defined in a relay agent filter applied to a DHCP address range, the appliance either assigns addresses from that range or denies the request based on the configured parameters.   
  
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*Figure* *31.5* *Relay* *Agent* *Filtering*

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To apply a relay agent filter to an address range:

1. Define a relay agent filter. For information, see <span style="color: #0000ff">[*Defining Relay Agent Filters*](https://infoblox-docs.atlassian.net/wiki/spaces/nios85draft/pages/26477992)</span><span style="color: #0000ff">*.*</span>
2. Apply the filter to a DHCP address range or range template, and specify that if the circuit ID or remote ID of a requesting host matches the filter definition, the appliance either grants or denies the address assignment. For information, see *<span style="color: #0000ff">[Applying](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[Filters](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[to](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[DHCP](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[Objects](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[.](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)
3. Define the access privileges of limited-access admin group for relay agent filters. For information, see *<span style="color: #0000ff">[Managing](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35481385)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35481385)*<span style="color: #0000ff">[Administrators](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35481385)</span>*.

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Defining Relay Agent Filters

To define a relay agent filter:

1. From the **Data** **Management** tab, select the **DHCP** tab -> **Filters** tab, and then expand the Toolbar and click **Add** -> **IPv4** **Relay** **Agent** **Filter**.  
or  
From any panel in the **DHCP** tab, expand the Toolbar and click **Add** -> **IPv4** **Relay** **Agent** **Filter**.
2. In the *Add* *IPv4* *Relay* *Agent* *Filter* wizard, complete the following:
  - **Name**: Enter a meaningful name for the filter. For example, you can enter the IP address or the name of the router acting as the relay agent. The name must be unique within a specific network.
  - **Comment**: Enter useful information about the filter.

3. Click **Next** to define the relay agent ID type. If you apply both ID types, the relay agent must provide both identifiers when submitting a DHCP address request.

  Select one of the following for both **Circuit** **ID** <span style="color: #3e3f40">and</span>**<span style="color: #3e3f40"> </span>** **Remote** **ID:**

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4. Click **Next** to enter values for required extensible attributes or add optional extensible attributes. For information, see *<span style="color: #0000ff">[Using](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35448912/Managing+Extensible+Attributes#Using Extensible Attributes)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35448912/Managing+Extensible+Attributes#Using Extensible Attributes)*<span style="color: #0000ff">[Extensible](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35448912/Managing+Extensible+Attributes#Using Extensible Attributes)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35448912/Managing+Extensible+Attributes#Using Extensible Attributes)*<span style="color: #0000ff">[Attributes](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35448912/Managing+Extensible+Attributes#Using Extensible Attributes)</span>*[.](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35448912/Managing+Extensible+Attributes#Using Extensible Attributes)

5. Save the configuration and click **Restart** if it appears at the top of the screen.

After you define a relay agent filter, you can assign it to a DHCP range. The appliance responds t> Macro (anchor)

o address requests based on the filter criteria. For information, see *<span style="color: #0000ff">[Applying](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[Filters](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[to](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[DHCP](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*[ ](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)*<span style="color: #0000ff">[Objects](https://infoblox-docs.atlassian.net/wiki/spaces/nios85/pages/35849428)</span>*.