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Configuration Guide - VXLAN

CloudEngine 12800 and 12800E V200R003C00

This document describes the configurations of VXLAN.
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
ARP Broadcast Suppression on a VXLAN

ARP Broadcast Suppression on a VXLAN

When tenants access each other for the first time, they send ARP requests, which are broadcast on Layer 2 networks and may cause a broadcast storm. To prevent this problem, ARP broadcast suppression can be enabled on Layer 2 VXLAN gateways.
NOTE:

This function is only supported for IPv4 over IPv4 networks but not for other combinations of underlay and overlay networks.

Figure 5-15 ARP broadcast suppression networking

On the network shown in Figure 5-15, the Layer 3 VXLAN gateway dynamically learns ARP entries of tenants and generates host information (host IP address, MAC address, VTEP address, and VNI ID) based on the ARP entries. The Layer 3 VXLAN gateway then uses MP-BGP or BGP EVPN to advertise the host information to MP-BGP or BGP EVPN peers. Layer 2 VXLAN gateways that are MP-BGP or BGP EVPN peers then use the learned host information for ARP broadcast suppression.

When Server1 accesses Server2 for the first time, Server1 broadcasts an ARP request message for Server2's MAC address. The process is as follows:

  1. Server1 broadcasts an ARP request message for Server2's MAC address.
  2. Device1, a Layer 2 VXLAN gateway, receives the ARP request message and searches host information.
    • If the host information on Device1 contains Server2 information, Device1 replaces the destination MAC address and target MAC in the broadcast ARP request message with Server2's MAC address, performs VXLAN encapsulation, and forwards the VXLAN packet.
    • If the host information on Device1 does not contain Server2 information, Device1 retains the destination MAC address in the broadcast ARP request message, performs VXLAN encapsulation, and forwards the VXLAN packet.
  3. Device2, a Layer 2 VXLAN gateway, receives and decapsulates the VXLAN packet and obtains the ARP request message. Device2 then determines whether the destination MAC address in the ARP request message is a broadcast MAC address.
    • If the destination MAC address is a broadcast address, Device2 broadcasts the ARP request message to the user side in the Layer 2 broadcast domain.
    • If the destination MAC address is not a broadcast address, Device2 forwards the ARP request message to the destination host Server2.
  4. Server2 receives the ARP request message and responds with an ARP reply message.
  5. Server1 receives the ARP reply message and generates an ARP entry in the ARP cache. By now, Server1 can communicate with Server2.
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Updated: 2019-05-05

Document ID: EDOC1100004207

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