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tatmotiv's avatar
tatmotiv
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Jul 09, 2015

TCP payload persistence (convert Cisco ACE l4-payload stickiness)

Hi all,

I'm currently transforming lots of Cisco ACE configurations to Big IPs running 11.6.0. On the ACE, there is a sticky method called "l4-payload" which can use a fixed offset and length setting in order to grab a specific portion of the TCP payload and generate a sticky entry based on that string (see http://www.cisco.com/c/en/us/td/docs/interfaces_modules/services_modules/ace/vA5_1_0/command/reference/ACE_cr/sticky.htmlwp1040212)

For example, I have the following sticky setting on the ACE that I need to convert to bigIP:

sticky layer4-payload my_l4_stickiness
 layer4-payload offset 30 length 20
 serverfarm my_serverfarm
 timeout 1
 replicate sticky

Which approach would you suggest? I think, I will need a combined iRule and universal persistence in order to achieve the same on the BigIP. Has anybody built something like that already? Any help is appreciated.

Thanks in advance!

Regards

Martin

application delivery
cisco ace
design
devops
iRules
LTM
TMOS

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  • tatmotiv's avatar
    tatmotiv
    Icon for Cirrostratus rankCirrostratus
    Jul 09, 2015

    Digging deeper into the issue, I thought about something like that...

    when CLIENT_ACCEPTED {
  TCP::collect 50
}

when CLIENT_DATA {
  set payload_first_50 [TCP::payload]
  set persist_string [substr $payload_first_50 29 20]
   log local0. "Fetched $persist_string as conn ID for client [IP::client_addr]."
  persist uie $persist_string 60
  TCP::release
}

    ... but I'm not sure if the data returned by [TCP::payload] is to be considered a string, thus being unsure whether using the substr method on it will return valid data.