MPLS vpls tunnel - MTU problem - wifi i think

RouterOS Forwarding Protocols
1

Hi,

I figured one situatsion.

This is wifi-client
In bridge is ether1 and wlan1

[admin@CLIENT] > interface pr
Flags: D - dynamic, X - disabled, R - running, S - slave 
 #     NAME                                TYPE       ACTUAL-MTU L2MTU  MAX-L2MTU MAC-ADDRESS      
 0  RS ether1                              ether            1500  1600       4076 00:0C:42:F7:14:52
 1  RS wlan1                               wlan             1500  1600            00:0C:42:F7:14:53
 2  R  bridge1                             bridge           1496  1600            00:0C:42:F7:14:53

This is wifi-AP
In bridge is wlan1 and vpls-lope

[admin@AP] > interface pr
Flags: D - dynamic, X - disabled, R - running, S - slave 
 #     NAME                                TYPE       ACTUAL-MTU L2MTU  MAX-L2MTU MAC-ADDRESS      
 0  R  ether1                              ether            1500  1600       4076 00:0C:42:CD:B6:FE
 1     ether2                              ether            1500  1598       2028 00:0C:42:CD:B6:FF
 2     ether3                              ether            1500  1598       2028 00:0C:42:CD:B7:00
 3     ether4                              ether            1500  1598       2028 00:0C:42:CD:B7:01
 4     ether5                              ether            1500  1598       2028 00:0C:42:CD:B7:02
 5  RS wlan1                               wlan             1500  1600            00:0C:42:CD:B6:FF
 6  R  bridge1                             bridge           1500  1530            02:39:5B:C5:A5:80
 7  R  lo                                  bridge           1500 65535            00:00:00:00:00:00
 8  RS vpls-lope                           vpls             1530  1530            02:39:5B:C5:A5:80

Problem:

[admin@CLIENT] > ping 10.11.12.1 size=1496
  SEQ HOST                                     SIZE TTL TIME  STATUS                                                                                                        
    0 10.11.12.1                               1496  63 8ms  
    1 10.11.12.1                               1496  63 10ms 
    sent=2 received=2 packet-loss=0% min-rtt=8ms avg-rtt=9ms max-rtt=10ms
  1. only paket size 1496 works.
  2. if client bridge mtu is 1500, then also 1496 pacet size works, but
    i cant work with winbox, onli mac-telnet works.
    This is all mtu problem.

but i think, problem is where?, wlan1 have not MAX-L2MTU support?
or need more information?
where is problem?

bridge “actual mtu” is lowest interface mtu(wlan1)
and that because this dont work?
i can change wlan1 mtu, but bridge actual mtu is 1500,
and because this dont work?

what i can do?

Best regards.
Aivar

2

It looks like something is stealing 4 bytes :slight_smile:

Your client bridge shows only 1496 actual bytes so I suspect an interface involved in the bridging is dragging it down.

Try removong wlan1 from the client bridge (assuming you have local access of course) and see if the bridge actual-MTU increases.

Perhaps a full export of the client and AP’s might help.

3

Hi.

More info… and my theory.
AP has bridge, and in bridge is interface wlan1 and vpls interface.

Now, what i can see and practis…:

  1. bridge “actual mtu” is lowest interface mtu(wlan1)
  2. MAX-L2MTU is missing interface wlan1
  3. wlan1 is always mtu 1500.
    i can change wlan1 mtu 1530,
    but bridge actual mtu is always 1500, then wlan1 is in bridge.
    short deskription is that.

Another story, that i have seen:
i have x86 mikrotik, many interfaces,
but 1 interface i dont have info MAX-L2MTU.
All other interfaces have MAX-L2MTU.
Happened, that i configure that interface mpls to work, but also strange things happened.
much the same things.

In conclusion

  1. bridge “actual mtu” is lowest interface mtu(wlan1)
    and wlan has only 1500, because MAX-L2MTU is missing.

By the way, MPLS is good, i want this situatsion.
but if wlan1 is only 1500, that is bad situatsion :frowning:


Aivar

4

wAP has MAX-L2MTU in wlan interface.
All works, like need.

But,
Omnitik series, SXT series, QRT series,Metallic, RB2011 series, RB751 … missing MAX-L2MTU in wlan,
ethernet has.

RB11GL - missing also ethernet.

If i start working problem, then mikrotik so nonsense :slight_smile:

Or you can help, something incomprehensible?

Aivar