Real Server Changes

Real Server Changes

This section is split in to the following sections:

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 jetNEXUS ALB-X
  • Request received by edgeNEXUS
  • Request routed to content servers
  • Response sent directly to client without passing through edgeNEXUS

DSR Diagram

Required Content Server Configuration

General

  • The content server default gateway should be configured as
    normal. (Not via the jetNEXUS ALB-X)
  • 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 jetNEXUS ALB-X
  • 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

  • Single Arm Mode – one interface is utilised but the service VIP and the real servers must be on different subnets.
  • Dual Arm Mode – two interfaces are utilised but the service VIP and real servers must be on different subnets.
  • In each case Single and Dual Arm the real servers need to configure their default gateway to the ALB-X interface address on the relevant subnet.

Gateway Example: Single Arm

Gateway: Dual Arm

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