Question

Exos server load balancing


How can I balance traffic between some http servers using extreme networks switches?
We use cisco IP SLA with static routes now, but I found no solutions with extreme networks switches. Does anyone know if there is "Server Load Balancing" functionality in ExOS?

9 replies

Userlevel 4
Can you show us some example of IP SLA which used by Cisco ? I may give you similar solution in EXOS.
My example with HTTP servers:

track 1 ip sla 1 reachability
!
track 2 ip sla 2 reachability
!
track 3 ip sla 3 reachability
!
ip sla 1 tcp-connect 192.168.2.71 9090 control disable
timeout 1000
threshold 1000
frequency 1
ip sla schedule 1 life forever start-time now
ip sla 2 tcp-connect 192.168.2.72 9090 control disable
timeout 1000
threshold 1000
frequency 1
ip sla schedule 2 life forever start-time now
ip sla 3
tcp-connect 192.168.2.73 9090 control disable
timeout 1000
threshold 1000
frequency 1
ip sla schedule 3 life forever start-time now
!
ip route 10.10.10.1 255.255.255.255 192.168.2.71 track 1
ip route 10.10.10.1 255.255.255.255 192.168.2.72 track 2
ip route 10.10.10.1 255.255.255.255 192.168.2.73 track 3


In this example IP SLA checks 9090 TCP ports of HTTP servers 192.168.2.71, 192.168.2.72, 192.168.2.73
If one of them goes down, specific static route will be switched off.

#sh ip route 10.10.10.1
Routing entry for 10.10.10.1/32
Known via "static", distance 1, metric 0
Routing Descriptor Blocks:
* 192.168.2.73
Route metric is 0, traffic share count is 1
192.168.2.72
Route metric is 0, traffic share count is 1
192.168.2.71
Route metric is 0, traffic share count is 1

Userlevel 4
You have configured the control disabled in IP SLA which means,

This requires that IP SLA responder has been configured on the other side. By default IP SLA uses control protocol to setup the connection and the responder adds timestamps etc for increase accuracy of IP SLA. If the other side is not a responder then the router will try to resend control packets and will eventually fail.

You should disable control packets whenever the other side is not a responder, so if you were running TCP connect to a real web server you would have to disable it because it would not be running as a responder. Your TCP succeeds because the port is open but in your case it is the control packets failing.

You are checking the reachability of the three server using the IP SLA TCP-connect protocol. If server is rechable then the static route is being installed in routing table. Please correct me if I am wrongly understand your requirement here.

In Extreme, we can NOT check the reachability of device using the TCP-connect feature where we can established the TCP session. However, we can check the reachability using the PING and ARP to make the determination. This is nothing but a way of health checking.

You can refer EXOS 15.4 concept guide and look for flow-redirect feature which is present on page # 731.
Sumit Tokle, thanks for reply!
The "control disable" means that cisco doesn't use IP SLA control protocol requests and checks TCP port, if port is open then the static route will be installed in routing table.
In IP SLA the "control" feature is enabled by default and it required on other side IP SLA responder which response on control protocol messages, it can be only cisco IOS devices.

I read about "Layer 2 Policy-Based Redirect" it is different functionality.
I know that EXOS can run scripts, is it possible to make script with similar solution?
Userlevel 4
Yes, you can create the script for the same.
Can you show example, please?
Userlevel 4
Let me see if I have any.
Have anyone received an example of these probes? We´ve been searching for a solution similar to ip-sla on EXOS but could not find it so far.
Userlevel 4
Hello Brunno,
Exos doesnt have server load balancing feature.
Extremeware products had those feature If I correctly remember.
S and K series support [legacy enterasys] support SLB.

I would recommend you to contact TAC.
They can help you if SLB in EXOS can be achieved using scripts.
Exos is rich with scripting features.

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