Direct Server Return

Direct Server Return, or DSR as it’s widely known (DR – Direct Routing in some circles) allows the server behind the load balancer to respond directly to the client bypassing the edgeNEXUS on the response. DSR is suitable for using with Layer 4 load balancing only therefore Caching and Compression are not available when enabled.
Layer 7 load balancing with this method will not work therefore there is no persistence support other than source IP. SSL/TLS load balancing with this method is not ideal as there is only source IP persistence support.

How it Works

• Client sends a request to the edgeNEXUS
• Request received by edgeNEXUS
• Request routed to content servers
• Response sent directly to client without passing through JetNEXUS

DSR Diagram

Required Content Server Configuration

General

• The content server default gateway should be configured as normal. (Not via the jetNEXUS)
• The content server and the load balancer must be in the same subnet

Windows

• The content server needs to have a loopback or Alias configure with the IP address of the Channel or VIP
  • Network metric must be 254 to prevent response to ARP requests
  • Add a loopback adapter in Windows Server 2012 – Click here
  • Add a loopback adapter in Windows Server 2003/2008 – Click here
• Run the following in a command prompt
  • netsh interface ipv4 set interface “net” weakhostreceive=enable
  • netsh interface ipv4 set interface “loopback” weakhostreceive=enable
  • netsh interface ipv4 set interface “loopback” weakhostsend=enable

Linux

• 1. Add a permanent loopback interface
• 2. Edit “/etc/sysconfig/network-scripts”
  • ifcfg-lo:1
    DEVICE=lo:1
    IPADDR=x.x.x.x
    NETMASK=255.255.255.255
    BROADCAST=x.x.x.x
    ONBOOT=yes
• 3. Edit “/etc/sysctl.conf”
  • net.ipv4.conf.all.arp_ignore = 1
    net.ipv4.conf.eth0.arp_ignore = 1
    net.ipv4.conf.eht1.arp_ignore = 1
    net.ipv4.conf.all.arp_announce = 2
    net.ipv4.conf.eth0.arp_announce = 2
    net.ipv4.conf.eth1.arp_announce = 2
• 4. Run “sysctl – p”

Gateway

Gateway mode allows you to route all traffic through the jetNEXUS, this allows traffic originating from the content servers to be routed via the edgeNEXUS to other networks via the interfaces on the edgeNEXUS unit. Using the device as a gateway device for content servers should be used when running in multi interface mode

How it works

• Client sends a request to the edgeNEXUS
• Request is received by edgeNEXUS
• Request sent to content servers
• Response sent to edgeNEXUS
• edgeNEXUS routes the response to the client

Required Content Server Configuration

• Content servers need to be configured to use the edgeNEXUS Eth0 IP address as their default gateway
• Content servers need to be configured to use the edgeNEXUS Eth1 IP address as their default gateway for dual arm configuration
• The content server and the load balancer must be in the same subnet

Windows

On windows the following commands must be run at the command prompt running in administrator mode. Where net is the name of the name of the interface:

• The content server needs to have a loopback or Alias configure with the IP address of the Channel or VIP
  • Network metric must be 254 to prevent response to ARP requests
  • Modify the netmask to be 255.255.255.255
  • Add a loopback adapter in Windows Server 2012 – Click here
  • Add a loopback adapter in Windows Server 2003/2008 – Click here
• Run the following in a command prompt
  • netsh interface ipv4 set interface “net” weakhostreceive=enable
  • netsh interface ipv4 set interface “loopback” weakhostreceive=enable
  • netsh interface ipv4 set interface “loopback” weakhostsend=enable

 

Linux

• 1. Add a permanent loopback interface
• 2. Edit “/etc/sysconfig/network-scripts”
  • ifcfg-lo:1
    DEVICE=lo:1
    IPADDR=x.x.x.x
    NETMASK=255.255.255.255
    BROADCAST=x.x.x.x
    ONBOOT=yes
• 3. Edit “/etc/sysctl.conf”
  • net.ipv4.conf.all.arp_ignore = 1
    net.ipv4.conf.eth0.arp_ignore = 1
    net.ipv4.conf.eht1.arp_ignore = 1
    net.ipv4.conf.all.arp_announce = 2
    net.ipv4.conf.eth0.arp_announce = 2
    net.ipv4.conf.eth1.arp_announce = 2
• 4. Run “sysctl – p”