---
name: "dhcrelay6"
section: "8"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/dhcrelay6"
---

# dhcrelay6(8)

Dynamic Host Configuration Protocol for IPv6 (DHCPv6) relay agent

## NAME

**dhcrelay6** – Dynamic Host Configuration Protocol for IPv6 (DHCPv6) relay agent

## SYNOPSIS

**dhcrelay6** \[**-dlov**\] \[**-E** *enterprise-number*\] \[**-I** *interface-id*\] \[**-R** *remote-id*\] **-i** *interface* *destination* *...*

## DESCRIPTION

The **dhcrelay6** utility provides a means for relaying DHCPv6 requests from a subnet to which no DHCP server is directly connected to one or more DHCPv6 servers on other subnets.

**dhcrelay6** listens for DHCPv6 requests on a given interface. When a query is received, **dhcrelay6** forwards it to the list of DHCP destinations specified on the command line. When a reply is received, it is sent on the network from whence the original request came.

The *destination* might be an address followed by a \`%' and an interface name, or just an interface name (e.g. "2001:db8::1%em0" or "em1"). When no address is specified, **dhcrelay6** will use multicast on the specified interface.

The options are as follows:

- **-d**

  Do not daemonize. If this option is specified, **dhcrelay6** will run in the foreground and log to *stderr*.

- **-E** *enterprise-number*

  Choose the *enterprise-number* that will be used by the Remote-ID option (this only has effect when using **-R**).

- **-I** *interface-id*

  The *interface-id* relay agent information option value that **dhcrelay6** should use on relayed packets. If this option is not specified, it will use the interface name by default.

  Avoid using this option when using Lightweight DHCPv6 Relay Mode (layer 2 relay), otherwise **dhcrelay6** will always send replies back to the client interface, which will break networks with multiple DHCPv6 layer 2 relay agents.

- **-i** *interface*

  The name of the network interface which will receive client DHCPv6 requests. For layer 3 mode at least one IPv6 local, site or global address has to be configured on this interface.

- **-l**

  Use the Lightweight DHCPv6 Relay Agent mode (layer 2 relaying).

- **-o**

  Add the Interface-ID option. This option is activated by default when using layer 2 relaying.

- **-R** *remote-id*

  Enable and add the specified Relay Agent *remote-id* to identify this relay segment.

- **-v**

  Show verbose messages. Implies **-d**.

## EXAMPLES

Relay multicast packets in the current network to a unicast address (the relay must have a global address in em0):

```
# dhcrelay6 -i em0 2001:db8::1000%em0
```

Listen to one subnet and multicast DHCPv6 packets to another (requires at least link-local addresses):

```
# dhcrelay6 -i em0 em1
```

Relay DHCPv6 packets with Interface-ID (option 18) using the input interface as its content:

```
# dhcrelay6 -o -i em0 2001:db8::1000%em0
```

Same thing as before but with a custom Interface-ID:

```
# dhcrelay6 -o -I "OpenBSD Router 1" -i em0 2001:db8::1000%em0
```

Use Lightweight DHCPv6 Relay Agent (layer 2 relay) in a bridged or switched network (no IPv6 address required). Only makes sense when em0 and em1 are configured in a [bridge(4)](/bridge/4.md), since **dhcrelay6** needs to drop the original DHCPv6 packets and send modified ones with Interface-ID option.

```
# dhcrelay6 -l -i em0 em1
```

Identify a segment using Lightweight DHCPv6 Relay Agent (layer 2 relay) with a Remote-ID (option 37) instead of an Interface-ID:

```
# dhcrelay6 -l -R "OpenBSD Router A" -i em0 em1
```

## SEE ALSO

[bridge(4)](/bridge/4.md), [dhcrelay(8)](/dhcrelay/8.md)

## STANDARDS

R. Droms, J. Bound, B. Volz, T. Lemon, C. Perkins, and M. Carney, *Dynamic Host Configuration Protocol for IPv6 (DHCPv6)*, RFC 3315, July 2003.

B. Volz, *Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Relay Agent Remote-ID Option*, RFC 4649, August 2006.

D. Miles, S. Ooghe, W. Dec, S. Krishnan, and A. Kavanagh, *Lightweight DHCPv6 Relay Agent*, RFC 6221, May 2011.

## AUTHORS

[dhcrelay(8)](/dhcrelay/8.md) was written by Ted Lemon ⟨*mellon@fugue.com*⟩ and reworked by Henning Brauer ⟨*henning@openbsd.org*⟩.

IPv6 support was implemented by Rafael Zalamena ⟨*rzalamena@openbsd.org*⟩.