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Configuration Guide - IP Service

CloudEngine 12800 and 12800E V200R005C00

This document describes the configurations of IP Service, including IP address, ARP, DHCP, DNS, IP performance optimization, IPv6, DHCPv6, and IPv6 DNS.
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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).
Centralized VXLAN Gateways Functioning as DHCPv6 Relay Agents

Centralized VXLAN Gateways Functioning as DHCPv6 Relay Agents

VXLAN support for DHCPv6 relay allows tenants to dynamically obtain IPv6 addresses using DHCPv6. This section describes the forwarding mechanisms of DHCPv6 relay in inter-VPN and intra-VPN scenarios.

DHCPv6 Client and Server on the Same VPN

On the network shown in Figure 8-13, the requirements are as follows:
  • Device1, Device2, and Device3 are Layer 2 VXLAN gateways that are connected to the Layer 3 VXLAN gateway over VXLAN tunnels. VXLAN tunnel setup and data forwarding are implemented on an IPv4 network.
  • VM1 and VM3 belong to the subnet with VNI 10. VM2 and VM4 belong to the subnet with VNI 20.
  • The DHCPv6 server connected to Device3 belongs to the same VPN but different subnet as VM1, VM2, VM3, and VM4.
After DHCPv6 relay is deployed on the VXLAN Layer 3 gateway, VM1, VM2, VM3, and VM4 can all function as a DHCPv6 client to dynamically request for IPv6 addresses from the DHCPv6 server.
Figure 8-13 VXLAN support for DHCPv6 relay in intra-VPN scenarios

DHCPv6 relay is deployed on the VBDIF interface of a Layer 3 VXLAN gateway. On the network shown in Figure 8-13, after DHCPv6 relay is deployed on VBDIF10, VM1 and VM3 that are on the subnet with VNI 10 can request for an IPv6 address from the DHCPv6 server.

The process of deploying DHCPv6 relay for such services as user online/offline and renewal on a VBDIF interface is similar to that on a common Layer 3 interface.

DHCPv6 Client and Server on Different VPNs

Figure 8-14 shows an inter-VPN scenario where VM1, VM2, VM3, and VM4 are in VPN10 while the DHCPv6 server is in VPN20.

Figure 8-14 VXLAN support for DHCPv6 relay in inter-VPN scenarios

In inter-VPN scenarios, DHCPv6 relay requires Option 68(vss-control) defined in RFC 6607. The Option 68 carries the VPN information corresponding to the DHCPv6 client. Upon receipt of a request, the DHCPv6 server searches the corresponding address pool based on Option 68 and assigns an IPv6 address to the DHCPv6 client.

The message exchange procedure for the user online service is as follows:
  1. VM1 sends a Solicit message with the destination address as FF02::1:2 to request for the server location.
  2. Upon receipt of the Solicit message on VBDIF10, the Layer 3 VXLAN gateway operates as follows:
    • Encapsulates the Solicit message in a newly constructed Relay-forward message.
    • Inserts Option 68, which indicates that the clients belong to VPN10, to the Relay-forward message.
    • Specifies the link address of the Relay-forward message to 2001:db8:1::1, the IP address of VBDIF10.
    • Specifies the source IPv6 address of the Relay-forward message to 2001:db8:2::1, the IP address of VBDIF100.
    • Specifies the destination IPv6 address of the Relay-forward message to 2001:db8:2::2, the IP address of the DHCPv6 server.
    • Searches the routing table based on the DHCPv6 server's IPv6 address and VPN information, inserts a VXLAN header to the Relay-forward message, and then sends the Relay-forward message.
  3. Upon receipt of the Relay-forward message, the DHCPv6 server operates as follows:
    • Parses the Solicit message from the Relay-forward message and searches the corresponding address pool based on the link-address and VPN information in Option 68 for IPv6 address assignment.
    • Encapsulates a newly constructed Advertise reply message to a Relay-reply message.
    • Sets the destination IPv6 address of the Relay-reply message to 2001:db8:2::1, the source IP address of the Relay-forward message.
    • Searches the routing table based on the destination IPv6 address and sends the Relay-reply message to the DHCPv6 relay.
  4. Upon receipt of the Relay-reply message, the Layer 3 VXLAN gateway decapsulates the Advertise reply message from the Relay-reply message and then sends the Relay-reply message to DHCPv6 clients.

The message exchange procedures for the user offline and renewal service procedures are similar to that for the user online service.

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Updated: 2019-04-18

Document ID: EDOC1100039535

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