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Mauricio_Garant's avatar
Mauricio_Garant
Icon for Nimbostratus rankNimbostratus
Feb 04, 2015

What happens if I increase the value from Http Maximum Header count and Http Maximum header Size

I have a LTM for Load Balancing Proxies Bluecoat. This error appers in ltm log:

 

an 30 11:48:29 BOGEAWF5LTMP01 err tmm1[11181]: 011f0011:3: HTTP header count exceeded maximum allowed count of 128 (Server side: vip=/Common/VS_PX_IGUANA profile=http pool=/Common/Proxy_Pool server_ip=10.1.150.10)

 

The Current HTTP Profile has 128 of Maximum Header Count and 36000 Maximum Header Size. The proxies has these limits greater:

 

Header count = 1,000 Header Length = 100,000

 

Please, I want to know if it´s possible configure these limits in the HTTP profile in the F5 without affecting the performance or service in the LTM.

 

APM
application delivery
availability
deployment
LTM
security
TMOS

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  • Arnaud_Lemaire's avatar
    Arnaud_Lemaire
    Icon for Employee rankEmployee
    Feb 04, 2015

    you can setup those limits, just tested on 11.6. big-ip will not pre allocate this amount of memory for each request, it will only if request is having such amoint of headers/size. So yes, if all your traffic is having thousand of headers per request you will consume more memory and potentially affecting overall max performances (less simultaneous connection for example) .

     

    Be aware that it s a security mesure to limit buffer overflow attacks on you backend for example, of resource exhaustion.

     

    internal db keys are also available to tell you big-ip to no reject by default if you exeed such values. you will have to ask support to get them.