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help. 2048 sized pings failing over ipsec tunnel

Chris Knipe
Beginner
Beginner

So because of the way active directory handles Group Policy I have been tasked with finding out why this is failing over the WAN.  Basically I know why, but don't know how to correct it.  I am trying to increase the MTU over an ipsec tunnel to 2048 to allow Microsoft Slowlink detection to occur.  http://support.microsoft.com/kb/227260 .  Basically, it sends 2 icmp packets.  One at a normal size and one at a size of 2048. In my case this is trying to occur over an ipsec tunnel and failing due to the MTU being at 1440.  I have seen a few articles about increasing it to 1500, but is there a way to increase the MTU to allow the 2048 sized icmp packets?

4 REPLIES 4

paolo bevilacqua
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

No, there is no way.

You can't fit a size 9 foot in a size 6 shoe.

Is it not possible to just increase the MTU on the tunnel on both sides to 2048?  I am getting the idea from this, that the maximum is 1500

http://www.cisco.com/en/US/tech/tk827/tk369/technologies_white_paper09186a00800d6979.shtml#NetPro

I have answered to you above already.

You can then do your experimenting, then report here the results.

thanks for clarifying /s

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