[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: MTU and Postfix

On 9/4/2011 5:40 AM, Camaleón wrote:
On Wed, 31 Aug 2011 16:09:23 +0000, Camaleón wrote:


I'm still monitoring this but if this is the "cure" to prevent such
errors, are there any expected drawbacks for lowering MTU "system-wide"?

Slightly lower overall performance when communicating with remote hosts. Almost zero difference on the LAN.

If you want optimal performance, you should enable jumbo frames on all LAN hosts (9000 bytes) since you're using GbE, and install an edge router that handles jumbo frames. Then you need not worry about any of this. Just make sure you find out from your service provider what size frames they use. Then program the WAN interface on the router with that frame size (MTU).

Problems such as yours are always caused by MTU mismatches. In most cases the mismatch is between the customer's edge device and the service provider equipment. Good routers will handle this just fine as long as the WAN port MTU is programmed to match the service provider equipment.

Worth noting is that different network technologies use different frame sizes. For instance, ethernet uses a 1514 octet frame. Fiber channel uses 2112. FDDI uses 4500. SONET is 2430.

You mentioned a "FTTH gigabit router" previously. Is this SP equipment or your independent equipment? The MTU mismatch most likely exists inside that box. If it was provided to you, then someone probably didn't program it correctly. It should have worked fine with different MTUs on both sides.


Reply to: