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doc: refresh tunnel documentation, add ospf example
Signed-off-by: Joachim Wiberg <[email protected]>
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‎doc/tunnels.md‎

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# Tunnel configuration
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# Tunnel Configuration
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Tunnel traffic from point A to point B
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Infix supports multiple tunnel encapsulation protocols for connecting
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remote networks or devices across an IP backbone. Tunnels encapsulate
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packets within IP datagrams, allowing traffic to traverse intermediate
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networks transparently.
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> [!IMPORTANT]
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> When issuing `leave` to activate your changes, remember to also save
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> your settings, `copy running-config startup-config`. See the [CLI
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> Introduction](cli/introduction.md) for a background.
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## Generic Routing Encapsulation (GRE)
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The support for GRE tunnels includes IPv4 and IPv6 tunnels both in GRE
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(IP) and GRETAP (MAC) modes.
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GRE tunnels provide a simple and efficient method to encapsulate various
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network layer protocols over IP networks. Infix supports both IPv4 and
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IPv6 tunnels in two modes:
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- **GRE (Layer 3):** Point-to-point IP tunnel for routing protocols and
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routed traffic
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- **GRETAP (Layer 2):** Ethernet tunnel for bridging Layer 2 networks
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> [!TIP]
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> If you name your tunnel interface `greN` or `gretapN`, where `N` is a
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> number, the CLI infers the interface type automatically.
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### Basic GRE Configuration
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A basic GRE tunnel for routing between two sites:
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```
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admin@example:/> configure
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admin@example:/config/> edit interface gre0
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admin@example:/config/interface/gre0/> set gre local 192.168.3.1 remote 192.168.3.2
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admin@example:/config/interface/gre0/> set ipv4 address 10.255.0.1 prefix-length 30
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admin@example:/config/interface/gre0/> leave
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admin@example:/>
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```
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This creates a Layer 3 tunnel between 192.168.3.1 and 192.168.3.2 using
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the outer IP addresses, with the tunnel itself using 10.255.0.0/30 for
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the inner IP addressing.
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### GRETAP Configuration
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GRETAP tunnels operate at Layer 2, allowing bridging across the tunnel:
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```
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admin@example:/config/> edit interface gre1
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admin@example:/config/interface/gre1/> set type gretap
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admin@example:/config/interface/gre1/> set gre local 192.168.3.1 remote 192.168.3.2
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admin@example:/config/interface/gre1/> leave
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admin@example:/> configure
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admin@example:/config/> edit interface gretap0
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admin@example:/config/interface/gretap0/> set type gretap
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admin@example:/config/interface/gretap0/> set gre local 192.168.3.1 remote 192.168.3.2
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admin@example:/config/interface/gretap0/> leave
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admin@example:/>
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```
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## Virtual eXtensible Local Area Network (VXLAN)
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GRETAP interfaces can be added to a bridge, bridging local and remote Ethernet
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segments. See the [Bridge Configuration](networking.md#bridge-configuration)
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for more on bridges.
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### OSPF over GRE
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GRE tunnels are commonly used to carry dynamic routing protocols like
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OSPF across networks that don't support multicast or where you want to
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create a virtual topology different from the physical network.
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The support for VXLAN tunnels includes IPv4 and IPv6.
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Example topology: Two sites connected via a GRE tunnel, running OSPF to
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exchange routes.
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**Site A configuration:**
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```
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admin@siteA:/> configure
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admin@siteA:/config/> edit interface gre0
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admin@siteA:/config/interface/gre0/> set gre local 203.0.113.1 remote 203.0.113.2
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admin@siteA:/config/interface/gre0/> set ipv4 address 10.255.0.1 prefix-length 30
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admin@siteA:/config/interface/gre0/> set ipv4 forwarding
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admin@siteA:/config/interface/gre0/> end
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admin@siteA:/config/> edit routing control-plane-protocol ospfv2 name default ospf
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admin@siteA:/config/routing/…/ospf/> set area 0.0.0.0 interface gre0
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admin@siteA:/config/routing/…/ospf/> leave
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admin@siteA:/>
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```
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**Site B configuration:**
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```
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admin@siteB:/> configure
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admin@siteB:/config/> edit interface gre0
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admin@siteB:/config/interface/gre0/> set gre local 203.0.113.2 remote 203.0.113.1
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admin@siteB:/config/interface/gre0/> set ipv4 address 10.255.0.2 prefix-length 30
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admin@siteB:/config/interface/gre0/> set ipv4 forwarding
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admin@siteB:/config/interface/gre0/> end
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admin@siteB:/config/> edit routing control-plane-protocol ospfv2 name default ospf
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admin@siteB:/config/routing/…/ospf/> set area 0.0.0.0 interface gre0
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admin@siteB:/config/routing/…/ospf/> leave
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admin@siteB:/>
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```
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Once configured, OSPF will establish a neighbor relationship through the
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tunnel and exchange routes between the sites. For more on OSPF
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configuration, see [Routing Configuration](routing.md).
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> [!NOTE]
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> Consider adjusting MTU on the tunnel interface to account for GRE
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> overhead (typically 24 bytes for IPv4, 44 bytes for IPv6) to avoid
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> fragmentation issues.
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## Virtual eXtensible Local Area Network (VXLAN)
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VXLAN is a network virtualization technology that encapsulates Layer 2
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Ethernet frames within Layer 4 UDP datagrams. It uses a 24-bit segment
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ID, termed VXLAN Network Identifier (VNI), allowing up to 16 million
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isolated networks.
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Infix supports both IPv4 and IPv6 for VXLAN tunnel endpoints.
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### Basic VXLAN Configuration
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```
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admin@example:/> configure
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admin@example:/config/> edit interface vxlan100
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admin@example:/config/interface/vxlan100/> set vxlan local 192.168.3.1
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admin@example:/config/interface/vxlan100/> set vxlan remote 192.168.3.2
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admin@example:/config/interface/vxlan100/> set vxlan vni 100
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admin@example:/config/interface/vxlan100/> leave
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admin@example:/>
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```
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The VNI uniquely identifies the VXLAN segment and must match on both
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tunnel endpoints.
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### VXLAN with Custom UDP Port
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The default VXLAN UDP destination port is 4789 (IANA assigned). In some
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cases you may need to use a different port:
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```
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admin@example:/> configure
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admin@example:/config/> edit interface vxlan100
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admin@example:/config/interface/vxlan100/> set vxlan local 192.168.3.1
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admin@example:/config/interface/vxlan100/> set vxlan remote 192.168.3.2
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admin@example:/config/interface/vxlan100/> set vxlan vni 100
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admin@example:/config/interface/vxlan100/> set vxlan remote-port 8472
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admin@example:/config/interface/vxlan100/> leave
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admin@example:/>
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```
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The remote-port setting allows interoperability with systems using
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non-standard VXLAN ports.
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> [!TIP]
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> If you name your VXLAN interface `vxlanN`, where `N` is a number, the
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> CLI infers the interface type automatically.

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