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350 lines
12 KiB
ReStructuredText
350 lines
12 KiB
ReStructuredText
:lastproofread: 2023-01-26
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.. _vxlan-interface:
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#####
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VXLAN
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#####
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:abbr:`VXLAN (Virtual Extensible LAN)` is a network virtualization technology
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that attempts to address the scalability problems associated with large cloud
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computing deployments. It uses a VLAN-like encapsulation technique to
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encapsulate OSI layer 2 Ethernet frames within layer 4 UDP datagrams, using
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4789 as the default IANA-assigned destination UDP port number. VXLAN
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endpoints, which terminate VXLAN tunnels and may be either virtual or physical
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switch ports, are known as :abbr:`VTEPs (VXLAN tunnel endpoints)`.
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VXLAN is an evolution of efforts to standardize an overlay encapsulation
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protocol. It increases the scalability up to 16 million logical networks and
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allows for layer 2 adjacency across IP networks. Multicast or unicast with
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head-end replication (HER) is used to flood broadcast, unknown unicast,
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and multicast (BUM) traffic.
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The VXLAN specification was originally created by VMware, Arista Networks
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and Cisco. Other backers of the VXLAN technology include Huawei, Broadcom,
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Citrix, Pica8, Big Switch Networks, Cumulus Networks, Dell EMC, Ericsson,
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Mellanox, FreeBSD, OpenBSD, Red Hat, Joyent, and Juniper Networks.
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VXLAN was officially documented by the IETF in :rfc:`7348`.
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If configuring VXLAN in a VyOS virtual machine, ensure that MAC spoofing
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(Hyper-V) or Forged Transmits (ESX) are permitted, otherwise forwarded frames
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may be blocked by the hypervisor.
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Configuration
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=============
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Common interface configuration
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------------------------------
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.. cmdinclude:: /_include/interface-common-without-dhcp.txt
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:var0: vxlan
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:var1: vxlan0
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VXLAN specific options
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-----------------------
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.. cfgcmd:: set interfaces vxlan <interface> vni <number>
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Each VXLAN segment is identified through a 24-bit segment ID, termed the
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:abbr:`VNI (VXLAN Network Identifier (or VXLAN Segment ID))`, This allows
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up to 16M VXLAN segments to coexist within the same administrative domain.
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.. cfgcmd:: set interfaces vxlan <interface> port <port>
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Configure port number of remote VXLAN endpoint.
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.. cfgcmd:: set interfaces vxlan <interface> source-address <IP address>
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Source IP address used for VXLAN underlay. This is mandatory when using VXLAN
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via L2VPN/EVPN.
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.. cfgcmd:: set interfaces vxlan <interface> gpe
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Enables the Generic Protocol extension (VXLAN-GPE). Currently, this is only
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supported together with the external keyword.
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.. cfgcmd:: set interfaces vxlan <interface> parameters external
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Specifies whether an external control plane (e.g. BGP L2VPN/EVPN) or the
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internal FDB should be used.
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.. cfgcmd:: set interfaces vxlan <interface> parameters neighbor-suppress
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In order to minimize the flooding of ARP and ND messages in the VXLAN network,
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EVPN includes provisions :rfc:`7432#section-10` that allow participating VTEPs
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to suppress such messages in case they know the MAC-IP binding and can reply
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on behalf of the remote host.
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.. cfgcmd:: set interfaces vxlan <interface> parameters nolearning
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Specifies if unknown source link layer addresses and IP addresses are entered
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into the VXLAN device forwarding database.
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.. cfgcmd:: set interfaces vxlan <interface> parameters vni-filter
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Specifies whether the VXLAN device is capable of vni filtering.
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Only works with a VXLAN device with external flag set.
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.. note:: The device can only receive packets with VNIs configured in
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the VNI filtering table.
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Unicast
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^^^^^^^
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.. cfgcmd:: set interfaces vxlan <interface> remote <address>
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IPv4/IPv6 remote address of the VXLAN tunnel. Alternative to multicast, the
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remote IPv4/IPv6 address can set directly.
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Multicast
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^^^^^^^^^
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.. cfgcmd:: set interfaces vxlan <interface> source-interface <interface>
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Interface used for VXLAN underlay. This is mandatory when using VXLAN via
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a multicast network. VXLAN traffic will always enter and exit this interface.
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.. cfgcmd:: set interfaces vxlan <interface> group <address>
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Multicast group address for VXLAN interface. VXLAN tunnels can be built
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either via Multicast or via Unicast.
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Both IPv4 and IPv6 multicast is possible.
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Multicast VXLAN
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===============
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Topology: PC4 - Leaf2 - Spine1 - Leaf3 - PC5
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PC4 has IP 10.0.0.4/24 and PC5 has IP 10.0.0.5/24, so they believe they are in
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the same broadcast domain.
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Let's assume PC4 on Leaf2 wants to ping PC5 on Leaf3. Instead of setting Leaf3
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as our remote end manually, Leaf2 encapsulates the packet into a UDP-packet and
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sends it to its designated multicast-address via Spine1. When Spine1 receives
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this packet it forwards it to all other leaves who has joined the same
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multicast-group, in this case Leaf3. When Leaf3 receives the packet it forwards
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it, while at the same time learning that PC4 is reachable behind Leaf2, because
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the encapsulated packet had Leaf2's IP address set as source IP.
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PC5 receives the ping echo, responds with an echo reply that Leaf3 receives and
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this time forwards to Leaf2's unicast address directly because it learned the
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location of PC4 above. When Leaf2 receives the echo reply from PC5 it sees that
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it came from Leaf3 and so remembers that PC5 is reachable via Leaf3.
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Thanks to this discovery, any subsequent traffic between PC4 and PC5 will not
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be using the multicast-address between the leaves as they both know behind which
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Leaf the PCs are connected. This saves traffic as less multicast packets sent
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reduces the load on the network, which improves scalability when more leaves are
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added.
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For optimal scalability, Multicast shouldn't be used at all, but instead use BGP
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to signal all connected devices between leaves. Unfortunately, VyOS does not yet
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support this.
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Single VXLAN device (SVD)
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=========================
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FRR supports a new way of configuring VLAN-to-VNI mappings for EVPN-VXLAN, when
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working with the Linux kernel. In this new way, the mapping of a VLAN to a
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:abbr:`VNI (VXLAN Network Identifier (or VXLAN Segment ID))` is configured
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against a container VXLAN interface which is referred to as a
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:abbr:`SVD (Single VXLAN device)`.
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Multiple VLAN to VNI mappings can be configured against the same SVD. This
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allows for a significant scaling of the number of VNIs since a separate VXLAN
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interface is no longer required for each VNI.
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.. cfgcmd:: set interfaces vxlan <interface> vlan-to-vni <vlan> vni <vni>
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Maps the VNI to the specified VLAN id. The VLAN can then be consumed by
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a bridge.
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Sample configuration of SVD with VLAN to VNI mappings is shown below.
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.. code-block:: none
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set interfaces bridge br0 member interface vxlan0
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set interfaces vxlan vxlan0 parameters external
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set interfaces vxlan vxlan0 source-interface 'dum0'
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set interfaces vxlan vxlan0 vlan-to-vni 10 vni '10010'
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set interfaces vxlan vxlan0 vlan-to-vni 11 vni '10011'
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set interfaces vxlan vxlan0 vlan-to-vni 30 vni '10030'
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set interfaces vxlan vxlan0 vlan-to-vni 31 vni '10031'
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Example
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-------
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The setup is this: Leaf2 - Spine1 - Leaf3
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Spine1 is a Cisco IOS router running version 15.4, Leaf2 and Leaf3 is each a
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VyOS router running 1.2.
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This topology was built using GNS3.
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Topology:
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.. code-block:: none
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Spine1:
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fa0/2 towards Leaf2, IP-address: 10.1.2.1/24
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fa0/3 towards Leaf3, IP-address: 10.1.3.1/24
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Leaf2:
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Eth0 towards Spine1, IP-address: 10.1.2.2/24
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Eth1 towards a vlan-aware switch
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Leaf3:
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Eth0 towards Spine1, IP-address 10.1.3.3/24
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Eth1 towards a vlan-aware switch
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**Spine1 Configuration:**
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.. code-block:: none
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conf t
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ip multicast-routing
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!
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interface fastethernet0/2
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ip address 10.1.2.1 255.255.255.0
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ip pim sparse-dense-mode
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!
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interface fastethernet0/3
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ip address 10.1.3.1 255.255.255.0
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ip pim sparse-dense-mode
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!
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router ospf 1
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network 10.0.0.0 0.255.255.255 area 0
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Multicast-routing is required for the leaves to forward traffic between each
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other in a more scalable way. This also requires PIM to be enabled towards the
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leaves so that the Spine can learn what multicast groups each Leaf expects
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traffic from.
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**Leaf2 configuration:**
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.. code-block:: none
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set interfaces ethernet eth0 address '10.1.2.2/24'
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set protocols ospf area 0 network '10.0.0.0/8'
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! Our first vxlan interface
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set interfaces bridge br241 address '172.16.241.1/24'
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set interfaces bridge br241 member interface 'eth1.241'
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set interfaces bridge br241 member interface 'vxlan241'
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set interfaces vxlan vxlan241 group '239.0.0.241'
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set interfaces vxlan vxlan241 source-interface 'eth0'
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set interfaces vxlan vxlan241 vni '241'
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! Our seconds vxlan interface
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set interfaces bridge br242 address '172.16.242.1/24'
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set interfaces bridge br242 member interface 'eth1.242'
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set interfaces bridge br242 member interface 'vxlan242'
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set interfaces vxlan vxlan242 group '239.0.0.242'
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set interfaces vxlan vxlan242 source-interface 'eth0'
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set interfaces vxlan vxlan242 vni '242'
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**Leaf3 configuration:**
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.. code-block:: none
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set interfaces ethernet eth0 address '10.1.3.3/24'
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set protocols ospf area 0 network '10.0.0.0/8'
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! Our first vxlan interface
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set interfaces bridge br241 address '172.16.241.1/24'
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set interfaces bridge br241 member interface 'eth1.241'
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set interfaces bridge br241 member interface 'vxlan241'
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set interfaces vxlan vxlan241 group '239.0.0.241'
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set interfaces vxlan vxlan241 source-interface 'eth0'
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set interfaces vxlan vxlan241 vni '241'
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! Our seconds vxlan interface
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set interfaces bridge br242 address '172.16.242.1/24'
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set interfaces bridge br242 member interface 'eth1.242'
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set interfaces bridge br242 member interface 'vxlan242'
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set interfaces vxlan vxlan242 group '239.0.0.242'
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set interfaces vxlan vxlan242 source-interface 'eth0'
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set interfaces vxlan vxlan242 vni '242'
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As you can see, Leaf2 and Leaf3 configuration is almost identical. There are
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lots of commands above, I'll try to into more detail below, command
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descriptions are placed under the command boxes:
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.. code-block:: none
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set interfaces bridge br241 address '172.16.241.1/24'
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This commands creates a bridge that is used to bind traffic on eth1 vlan 241
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with the vxlan241-interface. The IP address is not required. It may however be
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used as a default gateway for each Leaf which allows devices on the vlan to
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reach other subnets. This requires that the subnets are redistributed by OSPF
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so that the Spine will learn how to reach it. To do this you need to change the
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OSPF network from '10.0.0.0/8' to '0.0.0.0/0' to allow 172.16/12-networks to be
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advertised.
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.. code-block:: none
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set interfaces bridge br241 member interface 'eth1.241'
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set interfaces bridge br241 member interface 'vxlan241'
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Binds eth1.241 and vxlan241 to each other by making them both member
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interfaces of the same bridge.
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.. code-block:: none
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set interfaces vxlan vxlan241 group '239.0.0.241'
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The multicast-group used by all leaves for this vlan extension. Has to be the
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same on all leaves that has this interface.
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.. code-block:: none
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set interfaces vxlan vxlan241 source-interface 'eth0'
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Sets the interface to listen for multicast packets on. Could be a loopback, not
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yet tested.
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.. code-block:: none
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set interfaces vxlan vxlan241 vni '241'
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Sets the unique id for this vxlan-interface. Not sure how it correlates with
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multicast-address.
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.. code-block:: none
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set interfaces vxlan vxlan241 port 12345
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The destination port used for creating a VXLAN interface defaults to
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4789. Aconfiguration directive to support a user-specified destination port
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to override that behavior is available using the above command.
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Unicast VXLAN
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=============
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Alternative to multicast, the remote IPv4 address of the VXLAN tunnel can be
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set directly. Let's change the Multicast example from above:
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.. code-block:: none
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# leaf2 and leaf3
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delete interfaces vxlan vxlan241 group '239.0.0.241'
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delete interfaces vxlan vxlan241 source-interface 'eth0'
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# leaf2
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set interface vxlan vxlan241 remote 10.1.3.3
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# leaf3
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set interface vxlan vxlan241 remote 10.1.2.2
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The default port udp is set to 4789.
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It can be changed with ``set interface vxlan <vxlanN> port <port>``
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