Hi, I discovered that CAPsMAN in manager forwarding mode fragments traffic with full-frame MTU above 1200, even though L3 MTU of my LAN is 1500 (plenty of room for tunnel overhead). Since my (IPv6) WAN has L3 MTU 1280, I want to increase the CAPsMAN MTU to 1298 to avoid fragmentation of all WAN packets. (I currently use TCP MSS clamping for this purpose, but of course this doesn’t work for UDP.) Can MT provide a way to configure this limit, or choose it automatically based on link MTU and generate MSS rules like for PPP?
That’s interesting, I have had some issues at sites with DLink and HP 1810/1910 switches where L2 forwarded CAPSMAN was/is unreliable. At the Dlink site I replaced the old clunkers with CRS328 and the problems went away.
Another site with the 1810’s works much better if I use the CAPSMAN clients in TCP mode. I have just enabled Jumbo frames on the 1810s (the 1910 powering the wAPACs and cAPACs has jumbo on by default) and will see if the traffic problem comes back. On the 1810’s this changes the max frame size from 1518/1522(VLAN) to 9216 bytes. This is odd as this issue seems to have only crept in the last 12-24 months and has been intermittent and hard to nail down. Have CAPSMAN frames been getting bigger lately?
Mikrotik: For non Mikrotik switches what minimum L2 frame size do you require for L2 forwarded CAPSMAN frames? Can you put this figure in the CAPSMAN manual?