ip tcp adjust-mss interaction with PBR

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Nov 28th, 2007
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What is the order of operation for PBR and "ip tcp adjust-mss."


I have two ISP's (i.e. 2 default routes) and need to force pbr matched packets to use one ISP. When PBR is configured on the routers ingress interface, I get web browsing behavior that look just like "ip tcp adjust-mss" is skipped.



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Edison Ortiz Thu, 11/29/2007 - 08:12
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The adjust takes place before any routing or PBR decision.


Did you try testing your connection to the ISP without PBR ?


Perhaps the new ISP needs a lower adjustment than your current value.



mspiegelman Thu, 11/29/2007 - 09:23
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Connections over the link work fine until I enable PBR. Once PBR is enabled, I get partial page loads on some websites as if the adjust is not set. I haven't put a sniffer on it yet but it really looks like the adjust isn't happening.


Do you have a link to a page explaining the order of operation?

Edison Ortiz Thu, 11/29/2007 - 09:27
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No link from me :)


I usually do debugs in a lab with questions like this.

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