Interesting. If you get any feedback from Check Point regarding this please 
share. 

It is causing me some headache at the moment.

-Torkel


-----Opprinnelig melding-----
Fra: Mailing list for discussion of Firewall-1 [mailto:[EMAIL PROTECTED] På 
vegne av Ben Wilson
Sendt: 12. april 2007 15:09
Til: [EMAIL PROTECTED]
Emne: Re: [FW-1] MTU problems after upgrade

Yes, we have the same problem after moving to SecurePlatform from Nokia
IPSO.
Enabling fragmentation on the WAN link fixed our problem, but that won't
work for all types of traffic.

I have a call open with Check Point, but haven't gotten anywhere in 2
weeks.
I am really starting to regret moving to SecurePlatform...

--
Ben

> -----Original Message-----
> From: Mailing list for discussion of Firewall-1 [mailto:FW-1-
> [EMAIL PROTECTED] On Behalf Of Torkel Mathisen
> Sent: Thursday, April 12, 2007 6:23 AM
> To: [EMAIL PROTECTED]
> Subject: [FW-1] MTU problems after upgrade
> 
> Hi,
> 
> We recently upgraded our firewalls from R55 to R61/62. We also moved
> from Solaris to SPLAT in the same process.
> 
> After the upgrade we got lots of MTU problems. Traffic that worked
> before the upgrade now got blocked. Usually with "Invalid Sequence
> Number" and "Bad Ack Number".
> 
> We found out that most of this was because somewhere from source to
> destination the MTU was configured lower than 1500.
> 
> Like this:
> 
>       client -> server    TCP D=1443 S=39048 Ack=1315177946
> Seq=425805031 Len=1460 Win=49640
>       client -> server    TCP D=1443 S=39048 Push Ack=1315177946
> Seq=425806491 Len=266 Win=49640
>    server -> client       ICMP Destination unreachable (Needed to
> fragment: next hop MTU = 1440)
> 
> We have fixed this by changing the MTU setting on the servers. However
> I
> don't know if this is such a good idea as it will affect all traffic
to
> and from the server.
> 
> Why this worked on our old firewalls I can't say really, but I think
> they where just badly configured.
> 
> So my question is:
> 
> What is the best way of dealing with this kind of scenario?
> 
> Let's say you have a WAN link to a customer where the MTU is 1440 and
> your server/client is trying to send packets with 1460 bytes.
> 
> 
> Regards,
> Torkel
> 
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