I have Leased internet bandwidth and my upstream ISP has given me /30 WAN IP prefix .When I configured the WAN IP on my laptop for checking I am able to access only google services and content and can’t access any other websites . I changed the MTU settings on my laptop to 1424 from the default 1500 and I was able to access all the website. So I changed the MTU settings on my Mikrotik 1100X2AH to 1424 as I was not able to access the internet on default MTU, but still having the same issue.So I configured a SOHO netgear router with MTU 1424 and everything is working fine. Please help me to configure the MTU on Mikrotik .
This is the command I used to change MTU on 1100X2AH
/interface ethernet set ether1 mtu=1424
checked the interface, the MTU value had changed from 1500 to 1424 . Netgear SOHO router with MTU set to 1424 is working fine.
Please let me know if any more configuration is required on the Mikrotik .
Set the MTU to default (1500), then try pinging something on the internet without fragmentation first, do discover what mtu is accepted without fragmentation. And then set the MTU according to the result.
/ping 4.2.2.2 do-not-fragment size=1500
repeat the ping changing the size until you get an answer with no fragmentation needed. That is the size of the MTU
If after changing the MTU according to the result doesn’t help, you might need to change the MSS as well
Did your ISP state what their L3 MTU was set at? You need to match what they set their side to or you’ll end up with odd packet drops when packet reassembly happens.
Like the previous poster mentions do a ping test but instead of pinging the Internet ping the next hop towards your ISP.
You could set your L2 MTU to the one given by ISP and MTU to 100 bytes smaller. If the L3 MTU is smaller than what they expect it doesnt matter just as long as the L2 and L3 MTU are not bigger than what they expect.
For example i have my bridge in CCR set to 9000+ L2 MTU and MTU set to 65535. This helps with VPN throughput significantly.