Hello,

I have VPLS link between routers and I get packet drops, the usual ping might come back with 2 drops in 1,000 pings, when we use cisco rapid ping i get more errors, how can i check with Mikrotik packet drops? the fiber connecting these routers has no drops.

Many thanks,

did you check packet fragmentation?

they are pinging with 1500, how can I check packet fragmentation?

Hi,

just ping with "dont fragment" option set. Start with a payload if 1472 bytes (ICMP & IP Header is 28 bytes in total, so you have a size of 1500 bytes).
Then, decrease payload size till ping goes through unfragmented.

Take the value of your payload and add 28. Thats you actual MTU.

Edit: Mke sure, all devices in the MPLS path support the resulting MTU of the MPLS frames. If you like to transport full 1500 bytes inside MPLS, you need an "outer" MTU of 1522 bytes and if you like to use 802.1q you need additional 4 bytes, so 1526 bytes in total.

Regards,
Ape

I have set my MPLS MTU higher and I can ping up to 1546


ping 10.100.100.1 size=1546 do-not-fragment
SEQ HOST SIZE TTL TIME STATUS
0 10.100.100.1 1546 64 2ms
1 10.100.100.1 1546 64 2ms
2 10.100.100.1 1546 64 2ms

I don't understand why I get packet loss on this vpls link.

Thanks for your help.

Hi,

thank you for reporting back.

I drop just some thoughts:

• You can try "mtr -n --mpls" to determine the hop causing the packet loss

• Check if there are devices in the path with high CPU load, respectivly high single core load

• Is there an rate limit for ICMP packets?

• Is this limited to ICMP or is the packet loss occuring in general?

• I did a quick google with the search term "mikrotik vpls packet loss", some seem to be related to ROS version

I'm sorry, but it's hard to advice something precise.

Regards,
Ape

Thank you for your response.

mtr from linux pc?
None of the device has high CPU, most are between 20-30% rest of them 8%
no rate limit icmp
at the moment we are testing with icmp and seeing these packet loss, no loss on interface stats.
I have used the latest ROS version, and still this occurs.

thank you for your time.