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NE40E V800R010C00 Feature Description - NAT and IPv6 Transition 01

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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 Backup of Distributed NAT Devices

Centralized Backup of Distributed NAT Devices

Background

On the network shown in Figure 3-19, the CR and multiple BRASs are deployed in distributed NAT scenarios. In the event of a NAT board fault on a BRAS, the NAT function deployed on another BRAS works to implement inter-chassis hot backup, ensuring rapid recovery of BRAS and NAT services. This deployment mode, however, is costly for carriers. The CR and BRASs can be either directly connected or indirectly connected through tunnels. When a NAT board on a BRAS becomes faulty, user traffic is redirected to the NAT device connected to the CR for centralized NAT, ensuring service running and centralized backup of distributed NAT devices.

Figure 3-19  Centralized backup of distributed NAT

Deployment Solutions

In centralized NAT providing backup for distributed NAT, BRASs provide distributed NAT functions, and a NAT device attached to a CR implements centralized NAT functions. An interface board on each BRAS processes user packets and allows users to get online, and the CR does not process such packets. The BRASs and CR can be either directly connected or connected using tunnels:
  • Centralized NAT providing backup for distributed NAT in a non-tunnel scenario

    In Figure 3-20, when a NAT board on a BRAS (distributed NAT device) is working properly, the board performs NAT for private traffic to translate private IP addresses to public addresses and then forwards the private traffic to the Internet over routes.

    Figure 3-20  NAT process on distributed NAT devices

    In Figure 3-21, if a VSUF-80/160 on a BRAS fails and no backup service boards are equipped, the BRAS forwards private traffic directly over routes, without performing NAT. After the private traffic arrives at CR (centralized NAT device), the CR performs centralized NAT to translate private IP addresses to public IP addresses and forwards the traffic to the Internet.

    Figure 3-21  NAT process on the centralized device when a traffic switchover is performed
  • Centralized NAT providing backup for distributed NAT in an L3VPN scenario

    In Figure 3-22, VPN instances are deployed on private interfaces on the BRASs. If traffic is properly being transmitted, a BRAS (distributed NAT device) performs NAT and forwards the traffic to the Internet.

    Figure 3-22  NAT process on the distributed device

    In Figure 3-23, if the distributed NAT board on a BRAS fails, the BRAS forwards traffic directly to an L3VPN tunnel, without performing NAT. After receiving the traffic, the CR (centralized NAT device) performs centralized NAT to translate private IP addresses to public IP addresses and forwards the traffic to the Internet.

    Figure 3-23  NAT process on the centralized device when a traffic switchover is performed
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Updated: 2018-07-04

Document ID: EDOC1100027155

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