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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).
Distributed VXLAN Gateways Functioning as DHCPv6 Relay Agents

Distributed VXLAN Gateways Functioning as DHCPv6 Relay Agents

After DHCPv6 relay is enabled on a VXLAN gateway, terminal tenants can dynamically obtain IPv6 addresses using DHCPv6. This section describes the forwarding principles of distributed VXLAN gateways that function as DHCPv6 relay agents in intra-VPN (the DHCPv6 client and server reside on the same VPN) and inter-VPN (the DHCPv6 client and server reside on different VPNs) scenarios.

DHCPv6 Client and Server on the Same VPN

On the network shown in Figure 8-15:
  • Distributed Layer 3 VXLAN gateways are deployed on leaf1, leaf2, and leaf3, and they are connected over a Layer 3 VXLAN tunnel.
  • 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 leaf3 belongs to the same VPN but different subnet as VM1, VM2, VM3, and VM4.
After DHCPv6 relay is enabled on leaf1 and leaf2, VM1, VM2, VM3, and VM4 can all function as DHCPv6 clients to dynamically request for IPv6 addresses from the DHCPv6 server.
Figure 8-15 Distributed VXLAN Gateways Functioning as DHCPv6 Relay Agents in Intra-VPN Scenarios

DHCPv6 relay is enabled on the VBDIF interfaces of leaf nodes to which DHCPv6 clients are connected. In distributed VXLAN scenarios, the gateway address is the same for all the users in a subnet. On the network shown in Figure 8-15, the VBDIF interface address for all the users in the subnet with VNI 10 where leaf1 and leaf2 reside is the same.

The following uses client access on VM1 as an example to describe the forwarding process of DHCPv6 relay-enabled gateways.
  1. VM1 sends a Solicit packet to leaf1 to locate a DHCPv6 server.
  2. Leaf1 encapsulates the received Solicit packet into a newly constructed Relay-Forward packet and specifies a unique IPv6 address in the VPN as the source IPv6 address of the packet. Leaf1 encapsulates a VXLAN header into the Relay-Forward packet and forwards it over a VXLAN tunnel.
  3. Leaf3 decapsulates the received VXLAN packet and forwards the packet to the DHCPv6 server based on the destination IPv6 address.
  4. Upon receipt of the Relay-Forward packet, the DHCPv6 server assigns an IPv6 address from the local address pool. The DHCPv6 server encapsulates an Advertise packet into a Relay-Reply packet and specifies the source IPv6 address of the Replay-Forward packet as the destination IPv6 address of the Relay-Reply packet.
  5. Upon receipt of the Relay-Reply packet, leaf3 searches the routing table based on the destination IPv6 address and forwards the Relay-Reply packet to leaf1.
  6. Upon receipt of the Relay-Reply packet, leaf1 decapsulates the packet and then forwards the Advertise packet to VM1.

The forwarding process for user logout and lease renewal is the same as that for user access and therefore is not described.

DHCPv6 Client and Server on Different VPNs

On the network shown in Figure 8-16:
  • Distributed Layer 3 VXLAN gateways are deployed on leaf1, leaf2, and leaf3, and they are connected over a Layer 3 VXLAN tunnel.
  • 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 leaf3 belongs to a different subnet as VM1, VM2, VM3, and VM4.
  • VM1, VM2, VM3, and VM4 belong to VPN 10. The DHCPv6 server belongs to VPN 20.
After DHCPv6 relay is enabled on leaf1 and leaf2, VM1, VM2, VM3, and VM4 can all function as DHCPv6 clients to dynamically request for IPv6 addresses from the DHCPv6 server.
Figure 8-16 Distributed VXLAN Gateways Functioning as DHCPv6 Relay Agents in Inter-VPN Scenarios

In inter-VPN scenarios, the standard protocol-defined VSS-Control option (Option 68) must be supported on DHCPv6 relay-enabled gateways to carry information about VPNs to which clients belong. The following uses client access on VM1 as an example to describe the forwarding process of DHCPv6 relay-enabled gateways.

  1. VM1 sends a Solicit packet to leaf1 to locate a DHCPv6 server.
  2. Leaf1 encapsulates the received Solicit packet and the VSS-Control option (Option 68) that carries information about the VPN to which VM1 belongs into the newly constructed Relay-Forward packet and specifies a unique IPv6 address in the VPN as the source IPv6 address of the packet. Leaf1 encapsulates a VXLAN header into the Relay-Forward packet and forwards it over a VXLAN tunnel.
  3. Leaf3 decapsulates the received VXLAN packet and forwards the packet to the DHCPv6 server based on the destination IPv6 address.
  4. Upon receipt of the Relay-Forward packet, the DHCPv6 server searches for the corresponding address pool based on the VSS Control option (Option 68) and assigns an IPv6 address from the address pool. The DHCPv6 server encapsulates an Advertise packet into a Relay-Reply packet and specifies the source IPv6 address of the Replay-Forward packet as the destination IPv6 address of the Relay-Reply packet.
  5. Upon receipt of the Relay-Reply packet, leaf3 searches the routing table based on the destination IPv6 address and forwards the Relay-Reply packet to leaf1.
  6. Upon receipt of the Relay-Reply packet, leaf1 decapsulates the packet and then forwards the Advertise packet to VM1.

The forwarding process for user logout and lease renewal is the same as that for user access and therefore is not described.

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Updated: 2019-04-18

Document ID: EDOC1100039535

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