ACE backup-server and sticky

Question

Hi all,
a question:
     if a configure a serverfarm with backup-server
serverfarm host S_Das
  rserver DAS1
    backup-rserver DAS1_1
    inservice
  rserver DAS_1
    inservice standby
  rserver DAS2
    backup-rserver DAS2_1
    inservice
  rserver DAS_1
    inservice standby
sticky ip-netmask 255.255.255.255 address both SF_DAS
  timeout 10
  replicate sticky
  serverfarm S_Das
and rserver DAS1 goes down what will be behaviour of sticky and balancing?
New connection wel'll go towards DAS2 or a tricky and clever sticky take precedence? (i mean persistence on DAS1_1 that is my backup server..)
tnx
Das

Answer 1

Hi Danilo,
If your primary rserver goes down the sticky entries associated with that server will be automatically flushed from the sticky table so that
all new incoming connections will be diverted to your backup rserver.
In case that primary rserver comes back then:
- Existing connections on backup keep accessing backup.
- For new connection requests ACE looks up sticky entries, if there's already an entry for backup server the connections is sent to the standby rserver.
- If a new client request (connection) doesn't match any sticky entry for backup rserver ACE forwards this request to primary.
In case that you want to use the primary rserver for all the connections after coming back to operational state then the backup option would be configured like this:
rserver Primary
ip address 10.10.10.2
  inservice
rserver Standby
ip address 10.10.10.3
  inservice
serverfarm host Primary
  rserver Primary
    inservice
serverfarm host Standby
  rserver Standby
    inservice
policy-map type loadbalance http first-match slb
class class-default
serverfarm Primary backup Standby
HTH