strange masquerading error: failed TCP/UDP checksum for x.x.x.x!

strange masquerading error: failed TCP/UDP checksum for x.x.x.x!

Post by Marku » Thu, 12 Nov 1998 04:00:00


i try to set up masquerading for my lan and when i try to connect to the
internet from one of my boxes the connection seems to hang...

what happens is:

IE4 (on my nt-box) looks up the remote host and connects - then whatever
is requested is only partially downloaded.

my linux-box connects via isdn (dial on demand works)
firewall and masquerading seem to be set up o.k.
in /var/log/messages i get the message ip_fw_masquerade():change maddr
from 192.168.(localIP) to 149.222.(dnamic localIP)
then several of the following messages:
linux kernel: MASQ: failed TCP/UDP checksum for (whatever ip my nt-box
tries to connect to)

thanks for any help on what is going wrong here...


1. IP masquerading : TCP/UDP checksum errors

Firewall consisting of 2 linux boxes,
linux box with ISDN modem has (now) slackware 2.0.30 (with todays pre-31-2
patch), used to be 2.0.30, 2.0.29, 2.0.27.

using diald/ppp to connect to provider.

Things work fine and shiny, most of the time,
only every now and then we get the horrendous TCP/UDP checksum error,
resulting in stalled netscape

(just half an hour ago netscape hung itself after almost having dopwnlaoed
the 4.01 version ;( ...)

I checked the IP_masq webpages, and they suggest *not* using an MTU lower
than 1500 ??

Could anyone shed some light on this ??

Thanks muchos

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