Ethernet Interfaces¶

This document covers VLAN interfaces, physical Ethernet interfaces, and virtual Ethernet (VETH) pairs.

VLAN Interfaces¶

Creating a VLAN can be done in many ways. This section assumes VLAN interfaces created atop another Linux interface. E.g., the VLAN interfaces created on top of the Ethernet interface or bridge in the picture below.

A VLAN interface is basically a filtering abstraction. When you run tcpdump on a VLAN interface you will only see the frames matching the VLAN ID of the interface, compared to all the VLAN IDs if you run tcpdump on the lower-layer interface.

admin@example:/> configure
admin@example:/config/> edit interface eth0.20
admin@example:/config/interface/eth0.20/> show
type vlan;
vlan {
  tag-type c-vlan;
  id 20;
  lower-layer-if eth0;
}
admin@example:/config/interface/eth0.20/> leave

The example below assumes bridge br0 is already created, see VLAN Filtering Bridge.

admin@example:/> configure
admin@example:/config/> edit interface vlan10
admin@example:/config/interface/vlan10/> set vlan id 10
admin@example:/config/interface/vlan10/> set vlan lower-layer-if br0
admin@example:/config/interface/vlan10/> leave

As conventions, a VLAN interface for VID 20 on top of an Ethernet interface eth0 is named eth0.20, and a VLAN interface for VID 10 on top of a bridge interface br0 is named vlan10.

Note

If you name your VLAN interface foo0.N or vlanN, where N is a number, the CLI infers the interface type automatically.

Physical Ethernet Interfaces¶

Ethernet Settings and Status¶

Physical Ethernet interfaces provide low-level settings for speed/duplex as well as packet status and statistics.

By default, Ethernet interfaces defaults to auto-negotiating speed/duplex modes, advertising all speed and duplex modes available. In the example below, the switch would by default auto-negotiate speed 1 Gbit/s on port eth1 and 100 Mbit/s on port eth4, as those are the highest speeds supported by H1 and H2 respectively.

The speed and duplex status for the links can be listed as shown below, assuming the link operational status is 'up'.

admin@example:/> show interface eth1
name                : eth1
index               : 2
mtu                 : 1500
operational status  : up
auto-negotiation    : on
duplex              : full
speed               : 1000
physical address    : 00:53:00:06:11:01
ipv4 addresses      :
ipv6 addresses      :
in-octets           : 75581
out-octets          : 43130
...
admin@example:/> show interface eth4
name                : eth4
index               : 5
mtu                 : 1500
operational status  : up
auto-negotiation    : on
duplex              : full
speed               : 100
physical address    : 00:53:00:06:11:04
ipv4 addresses      :
ipv6 addresses      :
in-octets           : 75439
out-octets          : 550704
...
admin@example:/>

Configuring fixed speed and duplex¶

Auto-negotiation of speed/duplex mode is desired in almost all use-cases, but it is possible to disable auto-negotiation and specify a fixed speed and duplex mode.

Important

When setting a fixed speed and duplex mode, ensure both sides of the link have matching configuration. If speed does not match, the link will not come up. If duplex mode does not match, the result is reported collisions and/or bad throughput.

The example below configures port eth3 to fixed speed 100 Mbit/s half-duplex mode.

admin@example:/> configure
admin@example:/config/> edit interface eth3 ethernet
admin@example:/config/interface/eth3/ethernet/> set speed 0.1
admin@example:/config/interface/eth3/ethernet/> set duplex half
admin@example:/config/interface/eth3/ethernet/> set auto-negotiation enable false
admin@example:/config/interface/eth3/ethernet/> show
auto-negotiation {
  enable false;
}
duplex half;
speed 0.1;
admin@example:/config/interface/eth3/ethernet/> leave
admin@example:/>

Speed metric is in Gbit/s. Auto-negotiation needs to be disabled in order for fixed speed/duplex to apply. Only speeds 0.1(100 Mbit/s) and 0.01 (10 Mbit/s) can be specified. 1 Gbit/s and higher speeds require auto-negotiation to be enabled.

Ethernet statistics¶

Ethernet packet statistics¹ can be listed as shown below.

admin@example:/> show interface eth1
name                : eth1
index               : 2
mtu                 : 1500
operational status  : up
auto-negotiation    : on
duplex              : full
speed               : 1000
physical address    : 00:53:00:06:11:0a
ipv4 addresses      :
ipv6 addresses      :
in-octets           : 75581
out-octets          : 43130

eth-in-frames                : 434
eth-in-multicast-frames      : 296
eth-in-broadcast-frames      : 138
eth-in-error-fcs-frames      : 0
eth-in-error-oversize-frames : 0
eth-out-frames               : 310
eth-out-multicast-frames     : 310
eth-out-broadcast-frames     : 0
eth-out-good-octets          : 76821
eth-in-good-octets           : 60598
admin@example:/>

VETH Pairs¶

A Virtual Ethernet (VETH) pair is basically a virtual Ethernet cable. A cable can be "plugged in" to a bridge and the other end can be given to a container, or plugged into another bridge.

The latter example is useful if you have multiple bridges in the system with different properties (VLAN filtering, IEEE group forwarding, etc.), but still want some way of communicating between these domains.

admin@example:/> configure
admin@example:/config/> edit interface veth0a
admin@example:/config/interface/veth0a/> set veth peer veth0b
admin@example:/config/interface/veth0a/> end
admin@example:/config/> diff
interfaces {
+  interface veth0a {
+    type veth;
+    veth {
+      peer veth0b;
+    }
+  }
+  interface veth0b {
+    type veth;
+    veth {
+      peer veth0a;
+    }
+  }
}
admin@example:/config/>

Tip

This is another example of the automatic inference of the interface type from the name. Any name can be used, but then you have to set the interface type to veth manually.

Ethernet counters are described in ieee802-ethernet-interface.yang and infix-ethernet-interface.yang. There is a dedicated document on Ethernet Counters that provide additional details on the statistics support. ↩