Geneve
Geneve interfaces operate as virtual network ports. Administrators can apply standard network configurations on them, such as IP addressing, bridging, or firewall rules, just as they would on physical Ethernet ports.
The Geneve protocol encapsulates Layer 2 Ethernet frames originating from endpoints such as virtual machines, containers, or physical servers inside UDP packets. It unifies the features of earlier encapsulation protocols, including VXLAN, NVGRE, and STT, and addresses their limitations, such as fixed header structures and a lack of metadata support. Because of its extensibility, Geneve may eventually replace those older protocols.
Geneve tunnels are used to connect virtual switches residing within hypervisors, physical switches, middleboxes, and other network appliances.
Geneve tunnels operate over any standard IP network. In larger deployments, the underlying network (underlay) is often built using a Clos topology, also known as a leaf-and-spine or fat-tree topology.
Geneve header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver| Opt Len |O|C| Rsvd. | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Virtual Network Identifier (VNI) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Configuration
Common interface configuration
Configure one or more interface IP addresses.
<address> supports IPv4 and IPv6 in CIDR notation. For example, use
192.0.2.1/24 for IPv4 or 2001:db8::1/64 for IPv6.
Example:
set interfaces geneve gnv0 address 192.0.2.1/24
set interfaces geneve gnv0 address 2001:db8::1/64
Configure a clear, descriptive alias for the interface.
This alias appears in the show interfaces command and SNMP-based
monitoring tools.
Example:
set interfaces geneve gnv0 description 'This is an interface running on VyOS.'
Disable the interface.
The interface will be set to the administratively down
(A/D) state.
Example:
set interfaces geneve gnv0 disable
Configure a custom MAC address on the interface.
Example:
set interfaces geneve gnv0 mac '00:53:01:02:03:04'
Configure the MTU on the interface.
This value defines the largest packet size, in bytes, that the interface transmits without fragmentation.
Example:
set interfaces geneve gnv0 mtu 1600
Configure the MSS advertised in outgoing TCP SYN packets on the specified interface.
By clamping the MSS value in TCP SYN packets, you explicitly inform the remote side not to send packets larger than that size. This prevents connection issues that occur when Path MTU Discovery (PMTUD) fails.
The following options are available:
mss: Sets the MSS to a specific value, in bytes. Use this option if you need to enforce a specific MSS, for example, to troubleshoot connectivity issues or accommodate specific network requirements.
clamp-mss-to-pmtu: The router automatically calculates the MSS to be the interface’s MTU minus 40 bytes for IPv4 traffic (20 bytes for the IPv4 header and 20 bytes for the TCP header). This option is recommended to automatically set the proper value.
Configure how long an ARP entry remains valid after learning an IP-to-MAC address mapping on this interface.
The default duration is 30 seconds.
An ARP entry remains valid if it receives positive feedback from higher-level protocols.
Example:
set interfaces geneve gnv0 ip arp-cache-timeout 180
Configure ARP filtering on this interface.
Default behavior: The kernel responds to ARP requests on this interface only if the traffic would be routed back to the ARP sender through that specific interface.
If configured: The kernel responds to ARP requests on this interface for any IP address configured on the local host, regardless of which specific interface that IP address is assigned to, and regardless of the routing table. This reflects the Linux concept that IP addresses belong to the host, not individual interfaces.
Example:
set interfaces geneve gnv0 ip disable-arp-filter
Configure the interface for host or router behavior.
If configured, the interface switches to host mode, and IPv4 forwarding is disabled on it.
Example:
set interfaces geneve gnv0 ip disable-forwarding
Configure whether to forward IP-directed broadcast packets received on this interface.
Default behavior: IP-directed broadcast packets are dropped.
If configured: IP-directed broadcast packets are forwarded to all hosts on the destination subnet, as defined in RFC 1812 and RFC 2644.
Example:
set interfaces geneve gnv0 ip enable-directed-broadcast
Configure how to process gratuitous ARPs on this interface.
If configured, an IP-to-MAC address mapping is added to the ARP table based on gratuitous ARP requests or replies.
Note
If the ARP table already contains the IP address from a gratuitous ARP, its entry is updated regardless of whether this setting is configured.
Example:
set interfaces geneve gnv0 ip enable-arp-accept
Configure the source IP selection for ARP requests on this interface.
Default behavior: The kernel can use any IP address the host owns as the source IP address in ARP requests on this interface.
If configured: The kernel first attempts to select a source IP address configured on the interface that shares a common subnet with the target IP address. If there is no such subnet, the kernel selects the IP address it would normally use (based on the routing table to reach the target destination).
Example:
set interfaces geneve gnv0 ip enable-arp-announce
Configure which ARP requests will be ignored on this interface.
Default behavior: The kernel responds to ARP requests for any local IP addresses, regardless of which interface they are assigned to.
If configured: The kernel responds to ARP requests only if the target IP address is assigned to this specific interface.
Example:
set interfaces geneve gnv0 ip enable-arp-ignore
Configure proxy ARP on this interface.
If configured, the router (kernel) intercepts ARP requests for non-local IP addresses and replies with the MAC address of the interface that received the request. Subsequent packets destined to these IP addresses are forwarded to their actual destinations on remote subnets.
Example:
set interfaces geneve gnv0 ip enable-proxy-arp
Configure local proxy ARP on the interface.
If configured, the router (kernel) responds to ARP requests on this VLAN interface even if the target IP address resides on the same subnet and interface.
This is used to support network isolation requirements (RFC 3069) for private VLANs (PVLANs). In PVLAN configurations, hosts on isolated ports are NOT allowed to communicate directly with each other at Layer 2, but they can communicate with the upstream router.
By replying to inter-host ARP requests with its own MAC address, the router (kernel) directs inter-host traffic through itself instead of directly between hosts.
Note
This command works independently and does not require enabling the standard proxy ARP on the interface.
Local proxy ARP is also known as:
VLAN aggregation (RFC 3069).
Private VLAN (Cisco, Allied Telesyn).
Source-port filtering or port isolation (Hewlett-Packard).
MAC-Forced Forwarding (Ericsson).
Configure source IP address validation using RPF on this interface, as specified in RFC 3704.
The following options are available:
strict: Each incoming packet’s source IP address is checked against the Forwarding Information Base (FIB). If the interface is not the best route back to that source, validation fails, and the packet is dropped.
loose: Each incoming packet’s source IP address is checked against the FIB. If the source IP address is unreachable through any interface, validation fails.
disable: No source IP address validation is performed. All incoming packets are accepted.
RFC 3704 recommends enabling strict mode to prevent IP spoofing, such as DDoS attacks. For asymmetric or other complex routing scenarios, use loose mode.
Configure the interface to automatically obtain an IPv6 address using SLAAC, as specified in RFC 4862.
IPv6 hosts can configure themselves automatically when connected to an IPv6 network using the Neighbor Discovery Protocol via ICMPv6 router discovery messages. When first connected to a network, a host sends a link-local router solicitation multicast request for its configuration parameters. The router responds with a router advertisement packet containing Internet Layer configuration parameters.
Note
This method automatically disables IPv6 traffic forwarding on the interface.
Example:
set interfaces geneve gnv0 ipv6 address autoconf
Configure the interface to assign itself an IPv6 address using the EUI-64 method, as specified in RFC 4291.
Example:
set interfaces geneve gnv0 ipv6 address eui64 2001:db8:beef::/64
Disable the automatic assignment of a link-local IPv6 address to this interface.
Example:
set interfaces geneve gnv0 ipv6 address no-default-link-local
Configure the interface for host or router behavior.
If configured, the interface switches to host mode, and IPv6 forwarding is disabled on it.
Example:
set interfaces geneve gnv0 ipv6 disable-forwarding
Configure the MSS advertised in outgoing TCP SYN packets on the specified interface.
By clamping the MSS value in TCP SYN packets, you explicitly inform the remote side not to send packets larger than that size. This prevents connection issues when Path MTU Discovery (PMTUD) fails.
The following options are available:
mss: Set the MSS to a specific value, in bytes. Use this option to enforce a specific MSS, for example, to troubleshoot connectivity issues or accommodate specific network requirements.
clamp-mss-to-pmtu: The router calculates the MSS to be the interface’s MTU minus 60 bytes for IPv6 traffic (40 bytes for the IPv6 header and 20 bytes for the TCP header). This option is recommended to automatically set the proper value.
Configure IPv6 DAD on the interface.
The following options are available:
0: Disables DAD. No duplicate address detection is performed.
1: Enables DAD (default). Duplicate addresses are detected. The interface’s IPv6 operation continues for valid IPv6 addresses.
2: Enables DAD and, if a MAC-based duplicate link-local address is found, disables IPv6 operation on this interface.
Example:
set interfaces geneve gnv0 ipv6 accept-dad 2
Geneve options
Configure the remote endpoint IP address for the Geneve tunnel.
Configure VNI for the Geneve interface.
The VNI is a virtual network identifier. It allows multiple virtual networks to share the same physical infrastructure and remain isolated.
The VNI is also used to distribute traffic after it leaves the tunnel, for example, to map packets with overlapping IP addresses to specific routing tables.