New 532 OS version uses different syntax?

RouterOS General
1

I am trying to set up a mangle rule to change the MSS of my TCP packets to 1460, but the standard configuration as printed in the documentation for setting MSS is not accepted by my version of the RouterOS. Notably, it won’t accept the setting “tcp-options=syn-only”, and the new mangle configuration wants to know “chain-type”, while this is not specified in the documentation. My attempts at configuring an equivalent rule through WinBox are not working, either, as I am having difficulty associating the new parameter names with the old ones. I am probably missing something here that should be obvious, but I have been successful at getting all of the other features working on the RB532, except this one…

Can anyone tell me the proper syntax to use on the RB532 when lowering MSS for PPPoE, or how to set it up using WinBox?

Thanks,
Hitek

2

RB500 comes with pre-installed 2.9 version which is pretty much different in some areas. The manual is still being prepared, you can read some of it here:

http://www.mikrotik.com/docs/ros/2.9/

3

Yes, that is the manual that I have been using, as much as possible. Unfortunately, the configuration examples given at the end of the PPPoE section of that very manual are rejected when entered into the RouterOS. What is even worse, is that those very instructions are the one thing preventing me from having a completely working RB532 CPE solution. Any idea how to get the code found here working in the new RouterOS? This is the code from the 2.9 manual:

[admin@MikroTik] ip firewall mangle> add protocol=tcp tcp-options=syn-only \
\.. action=passthrough tcp-mss=1440
[admin@MikroTik] ip firewall mangle> print
Flags: X - disabled, I - invalid
  0   src-address=0.0.0.0/0:0-65535 in-interface=all
      dst-address=0.0.0.0/0:0-65535 protocol=tcp tcp-options=syn-only
      icmp-options=any:any flow="" src-mac-address=00:00:00:00:00:00
      limit-count=0 limit-burst=0 limit-time=0s action=passthrough
      mark-flow="" tcp-mss=1440

[admin@MikroTik] ip firewall mangle>

Thanks again,

Hitek

4 
[admin@MikroTik] > /ip firewall mangle add protocol=tcp tcp-flags=syn,!ack action=passthrough new-mss=1440 chain=forward
[admin@MikroTik] ip firewall mangle>

:sunglasses: :sunglasses: :sunglasses:

5

Thanks for that, even though I didn’t need to try it! After updating the box to the newest beta version, I noticed that the option was in the Winbox GUI, so it works well now.

Thanks again,

Hitek