Need some help on setting the max mtu on ccr 1036. Customers have complained about not being able to access certain websites. An example would be that they went to www.blick.com and that site would come up, but if they clicked on a link within the website the page would time out. After asking around people mentioned the mtu and possible fragments. I have tested the mtu on computer and found that 1464 was the largest possible setting that didn’t fragment. Now my question is if I set the max mtu mru at 1464 is that accounting for the overhead, or do I need to set my max mtu higher say 1492 and the endpoints will account for the overhead?
Hi,
how do you carry your customer pppoe_connections to pppoe_server ? over eoIP ?
Thnanks
Ethernet
You need to find the largest possible packet that fits on your link (not payload but entire packet) and set that as the MTU on the interface where the limitation is.
Normally that is a PPPoE interface with 1492, ethernet is 1500.
Besides you may find that some people filter all ICMP. You should not do that. Related ICMP must be passed!
However, to guard against others making mistakes you can add this mangle rule:
/ip firewall mangle
add action=change-mss chain=forward new-mss=clamp-to-pmtu passthrough=yes \
protocol=tcp tcp-flags=syn
However this only works when your MTU settings are correct.