hi, I recently bought the Chateau LTE12 router and was testing it with my 4G connection, and I can say it works beautifully.
When I connect it to my internet provider, I noticed this notification message appear on the Log screen:
lte1 mbim: network advertises higher mtu: 1550
I wanted to know how I could optimize this parameter and if any modification would really make sense to improve performance,
Thanks
What does field “Actual MTU” shows for lte1 interface? What would happen if you set MTU to 1550 for lte1?
on the WinBox gui it shows 1500, and if I try to manually set it up to 1550 and I click
on Apply it show a RouterOS WinBox Error dialog box saying "Couldn’t change Interface <lte 1> - could not set mtu (6)",
then the connection go immediately down and the router re-connect again, but with the same 1500 mtu value.
The same if I try to launch ‘/interface lte set lte1 mtu=1550’ from the Terminal, it
give a “failure: could not set mtu”, then again the connection go immediately down and the router re-connect again.
I have a similar message to OP, except is states: “lte1 mbim: network advertises lower mtu: 1430”. Is there something that I need to change?
Hi all
In MikroTik documentation (1, 2) we not have a details that we can change it.. and on some lte modems it’s just work and on some it’s do self-restart.
In Quectel documentation (EM12&EG12&EG18 \ AT Commands Manual), because a Chateau LTE12 use Quectel EG12 SoC we can found:
AT+QMTUINFO? ← Query MTU Value
+QMTUINFO:<pdp_cid>,<mtu_ipv4>,<mtu_ipv6>
<pdp_cid> PDP context identifier, a numeric parameter which specifies a particular PDP context.
<mtu_ipv4> MTU value of IPv4 interface.
<mtu_ipv6> MTU value of IPv6 interface.
and it’s all. No more info. The End.
At other AT Manuals..
*) “EG512R&EM1x0R Series” nothing more,
*) “RG50xQ&RM5xxQ Series” “5.6. AT+CGDCONT Define PDP Contexts” but this command better when ROS manage… what means we not have a big impact on it from our perspective… or I not know the proper/better documentation.
PS. You can manage MSS size for outgoing traffic, a smaller MTU then is set on interface. One mangle rule in firewall. Many examples at forum and official at wiki.
lte1 mbim: network advertises lower mtu: 1428
I’m curious what other people do with these “network advertises lower mtu” messages with LTE MBIM modems. In the PPP days, I always adjusted the MTU to match the what the carrier documents, and PPP profile would add the “clamp-to-mtu” mangle rule. And if you didn’t adjust the MTU, the upload performance was more variable/lower.
But with MBIM and LTE in V7, RouterOS doesn’t do this – even though it actually seem to know the MTU might be lower. And the default MTU in V7 seems to be MTU 1500, while in older RouterOS they did use a lower MTU by default for PPP/LTE.
My question is MTU adjustment actually necessary? I haven’t done extensive test with the default 1500… since I set MTU to match these “network advertise lower mtu” messages. I figured it’s better to avoid fragmentation, and give PMTUD a chance to work if the MTU is constrained someplace in the LTE network.
But I don’t see this as a recommendation in docs, nor any commentary in the forum (other than this post). Maybe any potential fragmentation isn’t a problem. Or some other framing upstream in modem/LTE network “fixes” it, but dunno. Thus bump in this topic.
P.S. If only I saw these…
but the two main carriers in US advertise “lower mtu”, generally 1430 or 1428… Thus the question.
@pcunite, Did you ever resolve this one?
In my experience, it seems to help with upload performance. But since LTE towers can load/congestion/etc, and netperf tools can have other variables…kinda hard to know for sure. But since 1500 is default MTU, UDP might get into trouble, so I’m not exactly a fan of changing it.
What I’d really like to know is if PMTUD discovery just always work in the upstream LTE, so maybe there is no need changing the MTU on the LTE interface based on the message. Dunno?
Anyway, I wish I had some more definitive advice on this one myself.