MRU stuck on 1500

RouterOS General
1

Hi, I am having difficulties with my new VDSL service using a DM200 modem in bridged mode, and Mikrotik HAP ac as PPPoE client and firewall/router.

As many others have noted, its probably an MTU or MRU issue because I can ping servers on the internet, can SSH to them, but web browsing does not work at all. If I connect my computer directly and initiate a PPPoE session, it all works fine.

So I tried setting the MRU to 1480, but it always reports as 1500 no matter what I try. Tried setting to both MTU/MRU to 1350, and plus all MTU/MRU/MRRU to 1480, but MRU always shows as 1500. Defaults show MTU 1480 and MRU 1500. I have tried the latest bug fix 6.36.4 and current 6.37.3 and both have same issue.

[admin@MikroTik] /interface pppoe-client> print
Flags: X - disabled, R - running 
 0  R name="PPPoE" max-mtu=1480 max-mru=1480 mrru=disabled interface=ether1 
      user="123456@isp.co.nz" password="password" profile=default 
      keepalive-timeout=60 service-name="" ac-name="" add-default-route=yes 
      default-route-distance=0 dial-on-demand=no use-peer-dns=yes 
      allow=pap,chap,mschap1,mschap2 

[admin@MikroTik] /interface pppoe-client> monitor PPPoE 
          status: connected
          uptime: 3m21s
    active-links: 1
        encoding: 
    service-name: 
         ac-name: cpcak-nthc-bng1
          ac-mac: 0C:A4:02:ED:55:5B
             mtu: 1480
             mru: 1500
   local-address: 100.20.30.40
  remote-address: 103.10.20.30
2

Check if the profile (TAB Profile in PPP) for your PPPoE connection has “Change TCP MSS” activated. You can try to leave the MTU also on 1500 because somewhere that MRU 1500 is provided.

3

Hi msatter, I tried setting the Change TCP MSS to off, on and default, and the MRU still doesn’t change from 1500. Setting MTU to 1500 doesn’t help either.

Thanks