Failover for server farm

Answered Question
Aug 19th, 2010
User Badges:

If you have a basic configuration on the ACE which consists of



VIP --> serverfarm -----> server1

                           -----> server 2


if one of the servers is removed or fails will the ACE detect this without probes being configured? and if so how does it detect the failure?


thanks

Correct Answer by yushimaz about 6 years 10 months ago


When you doesn't configure probe, ACE only detects server down with arp table.

It mean rserver goes down when arp timer is expired and rserver state will become ARP_FAILED.

Default arp timeout of rserver is 300 seconds as below.



ACE20/Admin# sh arp timeout


Context:Admin

Refresh Time:

   Learned Address      : 14400 seconds

   Configured Address   : 300 seconds

Retry Rate              : 10 seconds

Max retries per host    : 3

Periodic Sync Interval  : 5


You can change this value with 'arp interval' command on configuration mode.

However, this configuration change effects all configured address.

So, I recommend you configure probe.


Regards,

Yuji


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Loading.
ciscocsoc Thu, 08/19/2010 - 07:54
User Badges:
  • Silver, 250 points or more

Hi,


There is no automatic failure detection. You need to have some form of health probe.


HTH


Cathy

networker99 Thu, 08/19/2010 - 08:12
User Badges:

So if a server is rebooted or disconnected, it will still send data to it?

Correct Answer
yushimaz Thu, 08/19/2010 - 08:20
User Badges:
  • Cisco Employee,


When you doesn't configure probe, ACE only detects server down with arp table.

It mean rserver goes down when arp timer is expired and rserver state will become ARP_FAILED.

Default arp timeout of rserver is 300 seconds as below.



ACE20/Admin# sh arp timeout


Context:Admin

Refresh Time:

   Learned Address      : 14400 seconds

   Configured Address   : 300 seconds

Retry Rate              : 10 seconds

Max retries per host    : 3

Periodic Sync Interval  : 5


You can change this value with 'arp interval' command on configuration mode.

However, this configuration change effects all configured address.

So, I recommend you configure probe.


Regards,

Yuji


yushimaz Thu, 08/19/2010 - 08:31
User Badges:
  • Cisco Employee,

ACE will still send data until it detects server down.

After ACE detects rserver down, it doesn't send new connection to this server.

Regarding existing connection, it depends on the 'failaction' configuration on serverfarm mode.


Regards,

Yuji

Actions

This Discussion