Hi!


We have a little problema on client installation.

This client have a ADSL connection with dynamic IP. I have a modem router with bridge mode configuration and behind RB750 for PPPoE marking.

This configuration works fine but is impossible navigate to some web page's.


Is possible the problem are MTU or MSS???

MTU on PPPoE interface:
Max. MTU: 1480.
Max. MRU: 1480.
MRRU field is empty. (In other similar installations i configure 512)

MSS
On the automatic Mangle Rules (change Mss):
New TCP MSS: 1440 (input interface).
New TCP MSS: 1452 (output interface).
(In other similar installations is the same value).



I hope someone find this problem.



Thank you!

Perhaps the public IP address ends with a zero, some equipment does not accept an address that ends with a zero.

Which sites work of:

www.google.com
www.yahoo.com
www.speedtest.net

?

Thank you for a response

Perhaps the public IP address ends with a zero, some equipment does not accept an address that ends with a zero.

No, the public IP address ends with 32. This problem (ends with 0) is with all RB products?

Which sites work of:

http://www.google.com
http://www.yahoo.com
http://www.speedtest.net

?

google.com works fine but wikipedia.com don't work...

Is unbelievable because don't work whit I.E, or Chrome but if you do a ping response correctly and the tracert track is ok.

Note: If I configure client PPPoE in windows, whitout RouterOS, works fine for all web page's...


Any idea?

This problem (ends with 0) is with all RB products?

No, this issue has to do with with some websites.

google.com works fine but wikipedia.com don't work...

And the other 2 sites I mentioned?

google.com works fine but wikipedia.com don't work...

And the other 2 sites I mentioned?

Hi,

Your 3 websites works fine.

I'm lost with this problem...

Which RouterOS version is this?

MSS
On the automatic Mangle Rules (change Mss):
New TCP MSS: 1440 (input interface).
New TCP MSS: 1452 (output interface).
(In other similar installations is the same value).

By this did you mean that in similar installations the input/output interface show the same value (1440) or that other installations matched the two values shown?

I looked at a similar live setup running ROS 5.25. The two MSS settings are 1440 when the PPPoE client interface is set to 1480 MTU.

If you want to test whether that is the problem you could switch off the automatic MSS changes in the PPP profile and add manual rules instead.

You should be more specific about "don't work". What is the web browser response when you try wikipedia?

Add: Have you tried loading wikipedia avoiding all the "permanently moved" stuff?
http://en.wikipedia.org/wiki/Main_Page
or try the main host for the wikipedia site
http://208.80.154.225
wikipedia is obviously a virtual host site on a wikimedia server.

Did you checked the DNS ?

Which RouterOS version is this?

The last version v5.25.

You should be more specific about "don't work". What is the web browser response when you try wikipedia?

Add: Have you tried loading wikipedia avoiding all the "permanently moved" stuff?
http://en.wikipedia.org/wiki/Main_Page
or try the main host for the wikipedia site
http://208.80.154.225
wikipedia is obviously a virtual host site on a wikimedia server.

Sorry for my description, any web browser response is nothing, " about:blank". The PC send the request but when to receive, the content is nothing. No download the content..
If i check the acces about IP address i have the same result.

Did you checked the DNS ?

Yes, i tested the Open DNS and Google DNS.

MSS
On the automatic Mangle Rules (change Mss):
New TCP MSS: 1440 (input interface).
New TCP MSS: 1452 (output interface).
(In other similar installations is the same value).

By this did you mean that in similar installations the input/output interface show the same value (1440) or that other installations matched the two values shown?

I looked at a similar live setup running ROS 5.25. The two MSS settings are 1440 when the PPPoE client interface is set to 1480 MTU.

If you want to test whether that is the problem you could switch off the automatic MSS changes in the PPP profile and add manual rules instead.

Is very difficult change the configuration because this router is located at 500Km from my location and any change behaves lost connection.
The last week i was lost remote control even activating the safe mode...
I would like check with manual configuration beacause all my other similar connections have a two MSS settings are 1440 when the PPPoE client interface is set to 1480 MTU.



Thank you very much for responses,

Could you post the config - output from /export compact ?

Hi!

Sorry for no response in all this time.
Yesterday I found the same problemin other location, with other RB model, last firmware version and different public IP.

The RB configuration is ok, i'm sure but i don't understand how i check the webpage wih ping, this is ok but no download the web... the message is "web page found, waiting for response"

Yesterday i changed DNS and MRU.
MTU: 1480
MRU: 1492

Is possible the RB have this problem with vDSL connections?



Thank you!

Hi Waver
I had a similar issue with some FTTC connections, and I found out it was an MTU problem.
To troubleshoot this I would suggest you try pings with different sizes from the Mikrotik and to the Mikrotik from another location across the WAN link.
In my case packets with size=1455 and 1456 bytes were nor sent across nor fragmented, just dropped.
If you have a mac there is a ping flag (ping X.X.X.X -g 500 -G 1499) which tries all sizes in the range you specify. I am on Linux and had to try one by one
I am not sure why but my routerboard used MLPPP even for a single link, so it added 8 bytes of overhead instead of 6 to the packets.
My MTU on the LNS was 1494, and changing it to 1492 resolved the issue.
Also is your PPP profile set to change the tcp mss for that interface?
Hope this helps

Hi Waver
I had a similar issue with some FTTC connections, and I found out it was an MTU problem.
To troubleshoot this I would suggest you try pings with different sizes from the Mikrotik and to the Mikrotik from another location across the WAN link.
In my case packets with size=1455 and 1456 bytes were nor sent across nor fragmented, just dropped.
If you have a mac there is a ping flag (ping X.X.X.X -g 500 -G 1499) which tries all sizes in the range you specify. I am on Linux and had to try one by one
I am not sure why but my routerboard used MLPPP even for a single link, so it added 8 bytes of overhead instead of 6 to the packets.
My MTU on the LNS was 1494, and changing it to 1492 resolved the issue.
Also is your PPP profile set to change the tcp mss for that interface?
Hope this helps

Thank you,

By default, PPPoE client connections have a 1480 MTU & MRU. In this connections, when conection is UP the "status" indicates MTU 1480 and MRU 1492.
I changed MRU to 1492 (on general) but in a few minutes the MRU change automatically to 1480, how is possible?

Yes, my PPP profile change MSS for this interface (TCP MSS 1440).

Hi,

Now, when connection is established don't lost the manual MRU/MTU configuration but the connection don't works fine, Continuous without works whit some webpages

Any more idea? My client is desperate

Hi
have you tested the different packet sizes with ICMP to see if they go through?
As I said in my opinion there must be some packet sizes which are not fragmented nor passed through.

Hi
have you tested the different packet sizes with ICMP to see if they go through?
As I said in my opinion there must be some packet sizes which are not fragmented nor passed through.

Yes, now i tested the different packet sizes, and the maximun size for response is 1455 bytes, is very poor!

If i configure 1460 bytes, for example, don't have any response...

In other connections, i check the ping with 65500 bytes and response ok.

Which solution to this problem?



Thank you for your help.

Well, packets bigger than the MTU should be fragmented and sent anyway, not dropped. What is the MTU size on the LNS side for that connection?
What if you ping with 1700 as size?

Is possible configure the MRRU for receive the different packet size?

I don't know really the function of MRRU.

If i configure MRRU to 65535, is possible navigate correctly to every webpage's?




Thank you,

Well, packets bigger than the MTU should be fragmented and sent anyway, not dropped. What is the MTU size on the LNS side for that connection?
What if you ping with 1700 as size?

The MTU or MRU size on LNS side i don't know because is DSL connection, and i don't know how ISP works with this configurations.

If I check ping on 1700 i don't receive any response, time out.

Always, the router must be fragmented the packets, is this the problem, in this case, the router don't fragmented any packets.


Thank you,

@waver

I have the same situation. My L2TP server has MaxMRU/MaxMTU 1462/1462. Profile has Change TCP MSS set to yes. When my aDSL users connect through Telco LAC, in their status tab I see MTU 1462 and MRU 1492. It breaks my dynamic Mangle rule for out-interface all-ppp.

I've tried to connect on L2TP server with another MT router even with MaxMRU/MaxMTU 1500/1500 (as client) and on the server side in status tab I see MTU 1462 and MRU 1462 as it supposed to be.

Have you solved this problem and if yes, how?

Thanks!

I've figured out where was the problem.

As LAC is not MT, it has different config.