L2TP MTU and MRU sizes?

RouterOS General
1

Hi to all,

I have two routers RB493 and RB493AH both are connected to Internet via ADSL lines with MTU/MRU set to 1492 bytes.
Firstly I have created an bridge using EOIP over L2TP connection. EOIP MTU/MRU was set to 1500 bytes and L2TP MTU/MRU was set to 1452 (1492 - 40) bytes. In that case everything was fine regarding discarded packets and errors.

Then I have decided to simplify that solution by removing EOIP and adding L2TP directly into bridge. Protocol mode was modified to “rstp” on both bridges, bridging profile was added, local and remote addresses was removed from L2TP client and L2TP MRRU was set to 1600 bytes (most of hosts are running Windows).

Since than, bridge is working fine, but I have constant discarging of tx packets on client side of L2TP. I have tried several combination of MTU/MRU values with more or less same results.

Any suggestions?

2

i have some of these issues as well sometimes. i don’t know if its the hotspot i have in the bridge or just plain l2tp bridging. if you can narrow it down and open a ticket it would be beneficial. make sure you are on the latest version when testing. if you can post more details in this thread maybe we can nail it down together.

im using a bridge without any physical NIC, just a loopback bridge basically. I then add all the remote AP sites into a l2tp bridge profile with 1600 MRRU. I’m using cable modems at 1500 MTU so I just leave the L2tp tunnel at the default, 1460 i believe.

Sam