#mtu — Public Fediverse posts

Август 2026 отвал серверов. Почему ваш VLESS/Reality не работает

Помните времена, когда можно было купить VPS за доллар, накатить скрипт и забыть? Забудьте. Если последние недели вы проводите в чатах хостеров, созерцая бесконечные 502 Bad Gateway и context deadline exceeded, значит, вы в теме. ТСПУ окончательно перешли от блокировок по IP к «ковровому» анализу поведения трафика и манипуляциям с пакетами на уровне магистралов. Давайте разберем, что именно сломалось и какие костыли мы забиваем в систему, чтобы хоть как-то смотреть YouTube в 4K.

https://habr.com/ru/articles/1066610/

#vless #reality #dpi #mtu #cloudflare_warp #google_gemini #xhttp

Eclipse glasses to be made free as Cork 'best city' to see once-in-generation event

MTU Blackrock Castle Observatory is encouraging the public to collect appropriate glasses, plan a location with a clear western view and follow expert safety guidance throughout the eclipse on August 12

https://www.echolive.ie/corknews/arid-41887321.html

#mastodaoine #solareclipse #corkcity #cork #eclipse #MTU #astronomyevents #BlackrockCastleObservatory #astronomy

MTU, Frame Size и Jumbo Frames: анатомия сетевого пакета для инженера

Привет, Хабр! Меня зовут Светлана Каткова, я старший разработчик ПО

https://habr.com/ru/companies/yadro/articles/1055968/

#mtu #jumbo_frames #l2 #l3 #framesize

#Vodafone #DSLite hat mir mal wieder ein Bein gestellt: Konnte von einem Standort eines Freundes meinen heimischen Server (Vodafone-Kabel, richtiger Dual Stack) via #WireGuard nur mit einem Bruchteil der Geschwindigkeit erreichen (ca. 3 Mbit/s). War über einen längeren Zeitraum konstant gleich beschissen. In umgekehrter Richtung war es bei Transfers ähnlich.

Tja, was hat geholfen? MTU auf 1300 setzen (war auf 1420 gesetzt). Immer dasselbe, ey! 😵‍💫 Hatten wir übrigens auch so mit #OpenVPN-Verbindungen auf der Arbeit von Dual-Stack-Lite-Anschlüssen wegen Home-Office. Aber da musste auch erst mal drauf kommen... denke vernünftiges Erreichbarkeit via #IPv6 hätte auch geholfen.

⚠️ Also: Habt ihr Internet via TV-Kabel (mit DS-Lite) und eure Netzverbindung lahmt oder ist unzuverlässig? Versucht es mit einer niedrigen MTU.

#DualStackLite #Network #MTU #DualStack #Internet

So it appears like, for the last ~months, my MTU configuration was REALLY wrong

Hinted by the immich longhorn replica not rebuilding, but I also didn't know, the extreme slowness of any service using a db cluster where the master node wasn't in the same region

I had put the slowness on the shoulders of packets hopping a lot between regions, but it turns out, it was just db requests maxing past the configured MTU value, silently dropping

Now that BOTH the wireguard and flannel MTU values are set properly, everything is so damn snappy

This feels like new skin

#homelab #selfhosted #selfhosting #wireguard #mtu #vpn #mesh #longhorn #immich #flannel #devops #linux #opensource #networking

For the last ~6 months, my immich Longhorn PVC wouldn't rebuild replicas across regions, and timeout instead

Today, I figured I had misplaced my MTU configuration for the Wireguard network under k3s...

So some packets were getting dropped silently...

Woops

#kubernetes #k3s #longhorn #network #networking #wireguard #wg #mesh #homelab #selfhosted #selfhosting #mtu

Когда 50 байт ломают весь CI: охота на MTU mismatch в Docker + OpenStack

Пятница, 17:40. Билд красный, GitLab живой, curl отвечает за полсекунды — а git clone из контейнера молча висит две минуты и падает. Все инструменты говорят «всё ОК». Виновник — 50 байт, о которых никто не подумал. Разобраться

https://habr.com/ru/articles/1013208/

#mtu #gitlab_runner #docker #сеть

Copper Country businesses hold ‘Pike Tank’ entrepreneur event for students

HANCOCK, Mich. (WLUC) – A collaboration between the Copper Country Intermediate School District, Breakwater Federal Credit Union and…
#NewsBeep #News #US #USA #UnitedStates #UnitedStatesOfAmerica #Entrepreneurship #Business #Challenges #cte #Entrepreneur #growth #Hancock #InvestUP #Michigan #MTU #pike #shark #Small #student #tank #Tech
https://www.newsbeep.com/us/503712/

FWIW I just used https://calculator-apps.com/networking-calculators/mtu-mss-calculator to calculate 'proper' MTU/MSS values for my ip(6)tables rules.

Being paranoid about TCP Timestamps and SACK that's 1420 and 1440. I've set those and will need to remember to check if I see any weird issues....

#Linux #ipv6 #mtu

Well, now I feel stupid. I finally figured out why, since upgrading to Debian 13/trixie, there are some websites I couldn't connect to, but only over IPv6, they work fine on their IPv4 address.

Fucking MTU.

I'd for a long time had an IPv4 iptables rule to force the MSS (maximum segment size) on outbound packets to `1400`. But I never put in an equivalent for IPv6.

I use 'jumbo packets' on the LAN between desktop and server, which means an MTU of 4088 (for that pair of NICs). So anything forwarded out was using an MSS of 4088 as well.

The issue only showed up for *some* sites, and only for IPv6, and only on 13/trixie because:

1. 13/trixie uses openssl 3.x, not the older version, which has slightly different cipher suites etc in the default config.
2. IPv6 addressing makes packets that little bit bigger.
3. I've only ever observed the issue with MS Azure/Edge hosts.

What was happening was that the first part of the "Server Hello" after a "Change Cipher Spec, Client Hello" from my end was being lost, as the TCP level packet was too large and fragmented... but the first fragment was too large for my PPP link.

So, added an ip6tables rule to do the set-mss thing as well, and now it works.

#Linux #IPv6 #MTU #MSS #openssl #msedge #azure

@eXo_X5
[Translation of above post]
Homework: Try setting the #MTU to 1270 on any interface with an #IPv6 configuration under #linux!
You will witness how all IPv6 entries simply disappear.
IPv6 is not specified for an MTU below 1280.
One could know that – I didn’t.
It would be nice if wg-quick, when calculating an MTU below 1280, would either throw a meaningful error, or set 1280 as a minimum if IPv6 is configured.
Better occasional #fragmentation than no IPv6 at all.
5/6

@eXo_X5
[Translation of above post]
I have to admit that at this point I asked ChatGPT, and it actually gave the correct answer.
wg-quick doesn’t just bring the interface up, it also sets an appropriate MTU to prevent fragmentation.
But the #Bahn has configured its wifi network so strangely that the wifi interface itself only has an #MTU of 1350.
If you now subtract the 80 bytes of #WireGuard overhead, the WG interface is left with only 1270 bytes MTU.
4/6

I have gigabit fiber (up and down) out in rural #Kansas. I remain very thankful for the end to decades of dealing with weird antennas and such.

But today they switched from raw #Ethernet to #PPPoE, and although performance hasn't suffered to a noticeable extent, my #MTU has gone from 1500 to 1492. I am probably irrationally annoyed at this.

But dammit, PPP? In 2025? And going backwards on packet size?

S I G H.

There’s always another 🕳️ to go down. Now it’s a packet-level analysis of raw L2TPv3 pseudowires vs UDP encapsulated ones to find out •why• the raw ones come in with a lower automatic MTU than the UDP ones do. On the surface, this makes no sense. #NetEng #Labbing #L2TP #MTU #TunnelsAllTheWayDown

Und über @FreifunkHamburg sollte es an sich (theoretisch) dann auch keine #MTU Probleme geben können, weil wir hier im Gegensatz zur getunnelten Lösung über @freifunkMUC oder über HE die vollen 1500 bytes haben.

#IPv6 (zumindest via #radvd) ist bei uns nun temporär deaktiviert wegen #MTU Problemen, scheinbar zu diversen #Microsoft Seiten/Diensten. Dies macht sich dadurch bemerkbar, dass insbesondere größere Dateien/Seiteninhalte hier nicht geladen werden. Zur Zeit sieht es für uns aus, als ob sich #Microsoft nicht an IPv6-Standards hält (und insbesondere ICMPv6 Packet Too Big Nachrichten unkorrekterweise ignoriert). Aber wir sind da dran, das zu klären.

Jetzt nur über IPv4 sollte es aber vorerst gehen.

I have been having Secure Shell hangs when sending/receiving bulk data (large packets) between my workstation and a WAN server. I think I've discovered bad behavior somewhere in the WAN.

I figured it out by pinging the remote host using different sized packets with the Do Not Fragment bit set. Above a certain size, one is supposed to go from receiving ping responses to getting back ICMP error packets indicating the packet was too large and that fragmentation is needed, along with the MTU size to use. This called Path MTU Discovery.

Instead of that I get three behaviors: ping response for small packets, silence for midsized packets (bad!), and error response for too-large packets.

This is really bad news, and it seems TCP just stops working if it can't get those too-large packets through.

Anyway, the WAN provider apparently autonomously rebooted their equipment, and the problem is now gone, but it has been dogging me intermittently the last several months. It's a real pain when ssh craps out when cat'ing a long file or git fetch sessions hang.

I now have the start of a tool that I can use to monitor that bad behavior is happening, though.

#networking #IP #Internet #MTU #whine #software #WAN #SecureShell #ICMP #routing

Should I Block ICMP?
http://shouldiblockicmp.com/
#ycombinator #ICMP #traceroute #blackhole #traffic #ping #NDP #SLAAC #PMTUD #IPv4 #IPv6 #MTU #MSS #PLPMTUD

@sassdawe nice! #mtu