# DHCP Relay through GRE-Bridge

```{eval-rst}
| Testdate: 2023-05-11
| Version: 1.4-rolling-202305100734
```

This simple structure shows how to configure a DHCP Relay over a GRE Bridge
interface.

## Topology

The topology has 3 VyOS routers and one client. Between the DHCP Server and
the DHCP Relay is a GRE tunnel. The `transport` VyOS represent a large
Network.

```{image} _include/topology.webp
:alt: Ansible Example topology image
```


## Configuration

First, we configure the transport network and the Tunnel interface.

Transport:

```{literalinclude} _include/transport.conf
:language: none
```

DHCP-Server

```{literalinclude} _include/dhcp-server.conf
:language: none
:lines: 1-8
```

DHCP-Relay

```{literalinclude} _include/dhcp-relay.conf
:language: none
:lines: 1-8
```

After this, we need the DHCP-Server and Relay configuration.
To get a testable result, we just have one IP in the DHCP range.
Expand it as you need it.

DHCP-Server

```{literalinclude} _include/dhcp-server.conf
:language: none
:lines: 9-13
```

DHCP-Relay

```{literalinclude} _include/dhcp-relay.conf
:language: none
:lines: 9-10
```


## Test the result

Ping the Client from the DHCP Server.

```none
vyos@dhcp-server:~$ ping 192.168.0.30 count 4
PING 192.168.0.30 (192.168.0.30) 56(84) bytes of data.
64 bytes from 192.168.0.30: icmp_seq=1 ttl=63 time=1.02 ms
64 bytes from 192.168.0.30: icmp_seq=2 ttl=63 time=1.06 ms
64 bytes from 192.168.0.30: icmp_seq=3 ttl=63 time=1.21 ms
64 bytes from 192.168.0.30: icmp_seq=4 ttl=63 time=1.16 ms

--- 192.168.0.30 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 1.016/1.112/1.214/0.077 ms
```

And show all DHCP Leases

```none
vyos@dhcp-server:~$ show dhcp server leases
IP Address    MAC address        State    Lease start          Lease expiration     Remaining    Pool        Hostname
------------  -----------------  -------  -------------------  -------------------  -----------  ----------  ----------
192.168.0.30  00:50:79:66:68:05  active   2023/05/11 13:08:50  2023/05/12 13:08:50  23:59:16     DHCPTun100  VPCS
```