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Info
titleNote

Note: Single homed ports connecting a single device with the EVPN VXLAN fabric are not yet supported on VTEP devices. If a server is dual homed to two VTEPs and the connecting link to one of the VTEP fails, the server will still be considered a dual homed device even if there is only one active link connecting it to the fabric.


EVPN MH Basic Configuration

To configure EVPN multihoming on a LAG interface, the user needs to configure an Ethernet Segment identifier (ES-ID) and an Ethernet Segment System MAC. A type-3 ESI value is automatically generated by using these two parameters. The resulting 10-byte ESI value has the following format, where the XXs denote the 6-byte ES System MAC and the YYs denote the 3-byte local ES ID.

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For each Ethernet segment, both the ES System MAC and the ES ID must be the same on all the switches forming the EVPN MH redundancy group. However, switches can be configured with different system MACs for different Ethernet segments or share the same system MAC for all Ethernet segments.

Switch Configuration Example and Topology

In PICOS EVPN multihoming, there are two ways to forward BUM messages. You can choose one of these to apply to your EVPN fabric.

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Aliasing

The aliasing feature provides remote VTEP devices the ability to load balance Layer-2 unicast traffic through other VTEPs that have configured the same ES (Ethernet Segment). VTEP devices in the EVPN multihoming redundancy group always advertise the communicated information of the same ES to all remote VTEPs via MP-BGP protocol. If one of the VTEP device in an ES, say VTEP1 in the following figure, learns the MAC/ARP information and advertises it to the remote VTEP, say VTEP3. Then, VTEP3 adds not only the IP address of VTEP1 as the next hop, but also adds the IP addresses of other VTEPs in the EVPN multihoming redundancy group as the next hop, to automatically form equivalent paths between different VTEPs.

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EVPN multihoming aliasing function uses the ECMP hash fields "ingress-interface","ip-destination", "ip-source," "port-destination," "port-source," and "vlan" for equivalent paths calculation. By default, all these fields are enabled. Users can run the following CLI commands to enable or disable the ECMP hash fields:

set interface ecmp hash-mapping field ingress-interface disable

set interface ecmp hash-mapping field ip-destination disable

set interface ecmp hash-mapping field ip-protocol disable

set interface ecmp hash-mapping field ip-source disable

set interface ecmp hash-mapping field port-destination disable

set interface ecmp hash-mapping field port-source disable

set interface ecmp hash-mapping field vlan disable

On the remote VTEP, run the following EVPN MAC show commands to view the next hop. It shows the next hop interface is vplag, including all VTEPs in remote ES.

Code Block
admin@Xorplus# run show mac-address table
Total entries in switching table:   1
Static entries in switching table:  0
Dynamic entries in switching table: 1

VLAN        MAC address          Type         Age     Interfaces         User
----       -----------------     ---------    ----    ----------------   ----------  
N/A         00:0c:29:77:8b:15    Dynamic      300     vplag-0x1          xorp


admin@Xorplus# run show vxlan address-table
VNID          MAC address        Type       Interface          VTEP
-----------   -----------------  -------    ----------------   ---------------
10020         00:0c:29:77:8b:15  Dynamic                       10.226.14.253,10.226.14.254
Entries in access port:  0
Entries in network port: 1

Switch Configuration Example and Topology

In PICOS EVPN multihoming, there are two ways to forward BUM messages. You can choose one of these to apply to your EVPN fabric.

  • Head End Replication. This is the default way which needs no PIM configurations. The BUM message will be encapsulated and sent to all outgoing ports VTEPs of the same VNI by the access VTEP.
  • BUM tunnel. All VTEPs of the same VNI join the same multicast group, and use multicast routing protocol PIM to establish a multicast forwarding table entry for the multicast group. This method can reduce the traffic flooding caused by the head end replication of the BUM messages. This way needs to configure PIM protocol.

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To implement a seamless migration of servers VMs without changing network settings or disrupting the traffic forwarding, configure the same anycast gateway IP and the same virtual MAC (router MAC) on all four leaf switches to enable the anycast gateway function.

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Info
titleNOTE:

PICOS supports only one VXLAN segment mapping to one IP multicast group, which is the way to provide the optimal multicast forwarding. That is, to have multiple VXLAN segments share a single IP multicast group in the core network is not supported. 

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