# Ethernet Interfaces in VyOS

> Configure Ethernet interfaces in VyOS: IP addressing, MTU, VLAN, hardware offloading, speed/duplex, and port state monitoring for Yandex Cloud and VK Cloud

Source: https://opennix.org/en/docs/vyos/interfaces/vyos-ethernet/



Ethernet interfaces are the primary type of physical network interface in VyOS.

## Basic Configuration

### IP Addressing

Static IPv4 address:
```
set interfaces ethernet eth0 address 192.168.1.1/24
```

Static IPv6 address:
```
set interfaces ethernet eth0 address 2001:db8::1/64
```

Multiple addresses:
```
set interfaces ethernet eth0 address 192.168.1.1/24
set interfaces ethernet eth0 address 192.168.2.1/24
set interfaces ethernet eth0 address 2001:db8::1/64
```

### DHCP Client

DHCPv4:
```
set interfaces ethernet eth0 address dhcp
```

DHCPv6:
```
set interfaces ethernet eth0 address dhcpv6
```

### Interface Description

```
set interfaces ethernet eth0 description 'Primary LAN Interface'
```

### MAC Address

Changing the MAC address:
```
set interfaces ethernet eth0 mac '00:50:56:00:00:01'
```

## Physical Parameters

### Speed and Duplex

Automatic detection (default):
```
set interfaces ethernet eth0 speed auto
set interfaces ethernet eth0 duplex auto
```

Fixed values:
```
set interfaces ethernet eth0 speed 1000
set interfaces ethernet eth0 duplex full
```

Available speeds:
- `10` - 10 Mbps
- `100` - 100 Mbps
- `1000` - 1 Gbps
- `2500` - 2.5 Gbps
- `5000` - 5 Gbps
- `10000` - 10 Gbps
- `25000` - 25 Gbps
- `40000` - 40 Gbps
- `50000` - 50 Gbps
- `100000` - 100 Gbps
- `auto` - autodetection

Duplex modes:
- `half` - half duplex
- `full` - full duplex
- `auto` - autodetection

### MTU (Maximum Transmission Unit)

```
set interfaces ethernet eth0 mtu 1500
```

Typical MTU values:
- `1500` - standard Ethernet
- `9000` - Jumbo frames (requires hardware support)
- `1492` - for PPPoE (accounts for the 8-byte overhead)

## Flow Control

Data flow control to prevent congestion:

```
set interfaces ethernet eth0 flow-control enable
```

## Offloading (Hardware Acceleration)

### Generic Receive Offload (GRO)

```
set interfaces ethernet eth0 offload gro
```

### Generic Segmentation Offload (GSO)

```
set interfaces ethernet eth0 offload gso
```

### Large Receive Offload (LRO)

```
set interfaces ethernet eth0 offload lro
```

### Scatter-Gather (SG)

```
set interfaces ethernet eth0 offload sg
```

### TCP Segmentation Offload (TSO)

```
set interfaces ethernet eth0 offload tso
```

### UDP Fragmentation Offload (UFO)

```
set interfaces ethernet eth0 offload ufo
```

**Note**: Offload features can improve performance, but in some cases they may cause problems with certain traffic types or when using tunnels.

## Ring Buffer

Configuring the size of the ring buffers to optimize performance:

```
set interfaces ethernet eth0 ring-buffer rx 512
set interfaces ethernet eth0 ring-buffer tx 512
```

Increasing the buffer size can help when handling high loads.

## VLAN (802.1Q)

### Creating a VLAN Interface

```
set interfaces ethernet eth0 vif 100 address 192.168.100.1/24
set interfaces ethernet eth0 vif 100 description 'VLAN 100 - Guests'
```

### Multiple VLANs

```
set interfaces ethernet eth0 vif 10 address 192.168.10.1/24
set interfaces ethernet eth0 vif 10 description 'VLAN 10 - Management'

set interfaces ethernet eth0 vif 20 address 192.168.20.1/24
set interfaces ethernet eth0 vif 20 description 'VLAN 20 - Servers'

set interfaces ethernet eth0 vif 30 address 192.168.30.1/24
set interfaces ethernet eth0 vif 30 description 'VLAN 30 - Workstations'
```

### QinQ (802.1ad)

Double VLAN tagging:

```
set interfaces ethernet eth0 vif-s 100 vif-c 200 address 10.0.0.1/24
```

## Advanced IPv4 Settings

### ARP

ARP cache timeout:
```
set interfaces ethernet eth0 ip arp-cache-timeout 3600
```

Proxy ARP:
```
set interfaces ethernet eth0 ip enable-proxy-arp
```

ARP announce:
```
set interfaces ethernet eth0 ip enable-arp-announce
```

ARP ignore:
```
set interfaces ethernet eth0 ip enable-arp-ignore
```

### Source Validation

Source address validation to prevent spoofing:

```
set interfaces ethernet eth0 ip source-validation strict
```

Modes:
- `strict` - strict mode (RFC 3704)
- `loose` - loose mode
- `disable` - disabled

### Disable Forwarding

Disabling IP forwarding on the interface:
```
set interfaces ethernet eth0 ip disable-forwarding
```

## Advanced IPv6 Settings

### Autoconfiguration (SLAAC)

```
set interfaces ethernet eth0 ipv6 address autoconf
```

### Duplicate Address Detection (DAD)

Number of attempts to detect duplicate addresses:
```
set interfaces ethernet eth0 ipv6 dup-addr-detect-transmits 1
```

### Disabling IPv6

```
set interfaces ethernet eth0 ipv6 disable
```

### Disable Forwarding

```
set interfaces ethernet eth0 ipv6 disable-forwarding
```

## DHCP Options

### DHCPv4 Client

Client ID:
```
set interfaces ethernet eth0 dhcp-options client-id 'my-client-id'
```

Hostname:
```
set interfaces ethernet eth0 dhcp-options host-name 'vyos-router'
```

Vendor class ID:
```
set interfaces ethernet eth0 dhcp-options vendor-class-id 'vyos'
```

Default route distance:
```
set interfaces ethernet eth0 dhcp-options default-route-distance 210
```

Rejecting the default route from DHCP:
```
set interfaces ethernet eth0 dhcp-options no-default-route
```

### DHCPv6 Client

Prefix delegation:
```
set interfaces ethernet eth0 dhcpv6-options pd 0 interface eth1 address 1
set interfaces ethernet eth0 dhcpv6-options pd 0 length 56
```

Rapid commit:
```
set interfaces ethernet eth0 dhcpv6-options rapid-commit
```

Temporary addresses:
```
set interfaces ethernet eth0 dhcpv6-options temporary
```

## Binding to a VRF

```
set interfaces ethernet eth0 vrf RED
```

## Traffic Mirroring

Inbound traffic:
```
set interfaces ethernet eth0 mirror ingress eth1
```

Outbound traffic:
```
set interfaces ethernet eth0 mirror egress eth1
```

## Traffic Policies (QoS)

```
set interfaces ethernet eth0 traffic-policy in MY-SHAPER
set interfaces ethernet eth0 traffic-policy out MY-LIMITER
```

## Operational Commands

### Viewing State

All Ethernet interfaces:
```
show interfaces ethernet
```

A specific interface:
```
show interfaces ethernet eth0
```

Brief information:
```
show interfaces ethernet eth0 brief
```

### Physical Parameters

```
show interfaces ethernet eth0 physical
```

The output includes:
- Speed and duplex
- Auto-negotiation status
- Link state (link up/down)
- Error statistics

### Interface Counters

```
show interfaces ethernet eth0 statistics
```

### Clearing Counters

```
clear interfaces ethernet eth0 counters
```

### Traffic Monitoring

```
monitor interfaces ethernet eth0 traffic
```

### Traffic Capture

```
monitor traffic interface eth0
monitor traffic interface eth0 filter 'port 80'
```

## Configuration Examples

### Simple LAN Interface

```
set interfaces ethernet eth0 address 192.168.1.1/24
set interfaces ethernet eth0 description 'LAN'
set interfaces ethernet eth0 speed 1000
set interfaces ethernet eth0 duplex full
```

### WAN Interface with DHCP

```
set interfaces ethernet eth1 address dhcp
set interfaces ethernet eth1 description 'WAN'
set interfaces ethernet eth1 dhcp-options default-route-distance 210
```

### Trunk Port with Multiple VLANs

```
set interfaces ethernet eth2 description 'Trunk to switch'
set interfaces ethernet eth2 mtu 1500

set interfaces ethernet eth2 vif 10 address 192.168.10.1/24
set interfaces ethernet eth2 vif 10 description 'VLAN 10 - Management'

set interfaces ethernet eth2 vif 20 address 192.168.20.1/24
set interfaces ethernet eth2 vif 20 description 'VLAN 20 - Data'

set interfaces ethernet eth2 vif 30 address 192.168.30.1/24
set interfaces ethernet eth2 vif 30 description 'VLAN 30 - Voice'
```

### Interface with Jumbo Frames

```
set interfaces ethernet eth3 address 10.0.0.1/24
set interfaces ethernet eth3 description 'Storage network'
set interfaces ethernet eth3 mtu 9000
set interfaces ethernet eth3 speed 10000
set interfaces ethernet eth3 duplex full
```

### Dual-Stack (IPv4 + IPv6)

```
set interfaces ethernet eth0 address 192.168.1.1/24
set interfaces ethernet eth0 address 2001:db8:1::1/64
set interfaces ethernet eth0 description 'Dual-stack LAN'
set interfaces ethernet eth0 ipv6 dup-addr-detect-transmits 1
```

## Troubleshooting

### Interface in Down State

Check the physical connection:
```
show interfaces ethernet eth0 physical
```

Check whether the interface is disabled:
```
show interfaces ethernet eth0 | grep disable
```

Enable the interface if it is disabled:
```
delete interfaces ethernet eth0 disable
commit
```

### Performance Problems

Check for errors and collisions:
```
show interfaces ethernet eth0 statistics
```

Try disabling offload:
```
delete interfaces ethernet eth0 offload
commit
```

Increase the ring buffer:
```
set interfaces ethernet eth0 ring-buffer rx 1024
set interfaces ethernet eth0 ring-buffer tx 1024
commit
```

### Auto-negotiation Problems

Fix the speed and duplex:
```
set interfaces ethernet eth0 speed 1000
set interfaces ethernet eth0 duplex full
commit
```

### VLAN Problems

Make sure the parent interface is active:
```
show interfaces ethernet eth0
```

Check the VLAN ID:
```
show interfaces ethernet eth0 vif
```

## Best Practices

1. **Use descriptions** for all interfaces and VLANs
2. **Fix the speed/duplex** for critical connections
3. **Plan the MTU** - account for the VLAN tag (4 bytes)
4. **Test offload** - it may cause problems with some hardware
5. **Monitor errors** - check the counters regularly
6. **Document VLANs** - use clear descriptions
7. **Back up the configuration** before making changes

## Next Steps

- [Bridge](/docs/vyos/interfaces/vyos-bridge/) - for creating an L2 bridge between interfaces
- [Bond](/docs/vyos/interfaces/vyos-bond/) - for aggregating Ethernet links
- [VLAN](/docs/vyos/interfaces/vyos-vlan/) - detailed VLAN configuration