IP masquerading : TCP/UDP checksum errors

IP masquerading : TCP/UDP checksum errors

Post by The Acoustic Motorbik » Fri, 20 Jun 1997 04:00:00



Setup:
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

 
 
 

IP masquerading : TCP/UDP checksum errors

Post by Dalibor Carap » Sat, 21 Jun 1997 04:00:00



Quote:>Setup:
>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

AFAIK you use MTU 1500 for fast connections (local ethernet network). But
you should use lower MTU for modems or ISDN lines (I think that for modem is
269 (or 296) or something like that).

--
_______________________________________________________________________

 Dalibor Carapic - Fakultet Organizacije i Informatike
 http://www.foi.hr/~dcarapic
-----------------------------------------------------------------------

 
 
 

1. TCP/UDP checksum error with IP masquerading

I'm running IP masqurading on my linuxbox with a modem connected to
internet and Win95 computers on the LAN network. After a while I get
alot of checksum errors in /var/log/messages like:
Kernel: MASQ failed TCP/UPD checksum from x.x.x.x!
where x.x.x.x is some IP on the internet.

I'm using ipfwadm:
ipfwadm -F -p accept
ipfwadm -I -p accept
ipfwadm -O -p accept
ipfwadm -a masquerade -S 10.0.0.0/24 -D 0.0.0.0/0

What causes the checksum errors???

2. Why does kmix work with kernel 2.2.17 and not 2.2.18 ?

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

4. telnet vs. rlogin

5. IP MASQ : TCP/UDP checksum errors

6. Converting Unix to Windows stat $mtime

7. Masquerading and TCP/UDP checksum

8. Quake 2 for Linux is out

9. failed TCP/UDP checksum from <ip.address>!

10. IP Masq. failed TCP/UDP checksums

11. kernel: MASQ: failed TCP/UDP checksum from IP address

12. MASQ: Getting frequent TCP/UDP checksum errors