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    Accelerating Routing Convergence Through BGP+BFD (Layer 3)

    Last updated: 2024-01-13 16:02:36
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      This document describes how to accelerate routing convergence between customer IDC and private network by initiating BGP routing protocol on the local IDC switch and configuring bidirectional forwarding detection (BFD) on Tencent Cloud direct connect gateway.

      Background

      
      Note:
      In a connection using static routes, we recommended that you use static routes and BFD/NQA to achieve route convergence.
      The connection connects the IDC switch and the layer 3 network sub-interface of Tencent Cloud switch, thereby connecting IDC and Tencent Cloud network.
      Implement mutual access to resources through VPC/CCN.
      Implement routing convergence through BGP+BFD/NQA.

      Prerequisite

      You have built a VPC as instructed in Building Up an IPv4 VPC.
      You have applied for a connection as instructed in Applying for Connection and completed the preparatory construction.

      Configuration Guide

      Step 1. Create a direct connect gateway

      For more information, see Creating a Direct Connect Gateway.

      Step 2. Create a dedicated tunnel

      The tunnels created on the connections vary depending on the access method.
      The tunnels created on your own connections are exclusive dedicated tunnels, which are applicable to scenarios with requirements for high-bandwidth access and exclusive access. For more information, see Exclusive Virtual Interface.
      The tunnels created on our partners' connections pre-established in Tencent are shared dedicated tunnels, which are applicable to scenarios where there is no need for high-bandwidth access and the cloudification time is short. For more information, see Shared Dedicated Tunnel.

      Step 3. Configure health check

      For more information, see Dedicated tunnel health check.

      Step 4. Completing the IDC local configuration as instructed in Huawei NE Series Routers

      This document takes Huawei CE switch as an example. For other local configurations, see Huawei NE Series Routers. If you can't implement the layer 3 sub-interface connection due to special reasons, you can try layer 2 sub-interfaces. For details, see Mode 2.
      (Recommended) Mode 1: Layer 3 sub-interface+BGP
      # Set sub-interfaces for layer 3 connection
      interfaces
      <interface_number>.<sub_number>
      description <interface_desc>
      dot1q termination vid <vlan id>
      ip address <subinterface_ipaddress>
      <subinterface_netmask>
      speed <interface_speed>
      duplex full
      undo negotiation auto
      commit
      # Set eBGP 
      bgp <as_number>
      router-id <route_id>
      peer <bgp_peer_address> as-number
      <bgp_peer_as_number>
      peer <bgp_peer_address> password cipher
      <bgp_auth_key>
      peer <bgp_peer_address> description
      <bgp_desc>
      ipv4-family unicast
      peer <bgp_peer_address> enable
      commit
      # Set BFD configuration of eBGP
      bgp <as_number>
      router-id <route_id>
      peer <bgp_peer_address> bfd min-tx-interval
      1000 min-rx-interval 1000 detect-multiplier 3
      Mode 2: Layer 2 Vlanif interface+BGP (It is recommended to disable STP for layer 2 interfaces)
      # Set ports
      interfaces
      <interface_number>
      description
      <interface_desc>
      port link-type
      trunk
      undo shutdown
      speed
      <interface_speed>
      duplex full
      undo negotiation
      auto
      stp disable ** (****Disable****stp****STP****)**
      commit
      # Set virtual tunnels
      vlan
      <subinterface_vlanid>
      description
      <subinterface_desc>
      # Set logic interfaces
      interface Vlanif
      <subinterface_vlanid>
      description <subinterface_desc>
      ip address
      <subinterface_ipaddress> <subinterface_netmask>
      # Configure interface VLAN
      interfaces
      <interface_number>
      port trunk
      allow-pass vlan <subinterface_vlanid>
      commit
      # Set eBGP 
      bgp
      <as_number>
      router-id
      <route_id>
      peer
      <bgp_peer_address> as-number <bgp_peer_as_number>
      peer
      <bgp_peer_address> password cipher <bgp_auth_key>
      peer
      <bgp_peer_address> description <bgp_desc>
      ipv4-family
      unicast
      peer
      <bgp_peer_address> enable
      # Set BFD configuration of eBGP
      bgp <as_number>
      router-id <route_id>
      peer <bgp_peer_address> bfd min-tx-interval
      1000 min-rx-interval 1000 detect-multiplier 3
      commit

      How to Set Keepalive and Holdtime Parameters

      After establishing a BGP connection between two peers, the two peers periodically send keepalive messages to the peer to maintain the validity of the BGP connection. If a router does not receive a keepalive message or any other type of packet from the peer within the specified holdtime, the BGP connection is considered to have been interrupted and thus the BGP connection is interrupted.
      The keepalive-time and hold-time values are determined through negotiation between the two peers. The smaller hold-time value in the Open message of both peers is the final hold-time value. The smaller value between the result of the negotiated hold-time value divided by 3 and the locally configured keepalive-time value is used as the final keepalive-time value. When the BGP connection is established, the recommended holdtime is 180 seconds (default value used by most vendors).
      If the configured holdtime is less than 30 seconds, the linkage may interrupt the neighbor session in normal cases, and linkage jitter detection is required. You are advised to enable BFD to improve convergence performance.
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