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Questions tagged [mtu]

MTU (Maximum Transfer Unit) refers to the largest size of the datagram that a layer of a communication protocol can transmit.

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WIN machine + change the MTU from 1500 to 9000 + do we need to restart the network interface

we change the MTU on the WIN machine ( 2008 ) from 1500 to 9000 Do we need to restart the network interface in order to take affect ?
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How to configure untagging of packets in a Linux VLAN aware software bridge for KVM quest?

I'd like to know how does a Linux VLAN award software bridge (eg. one which has VLAN filtering activated) handle the configuration where a bridge receives full size (eg. full MTU size) packet with a ...
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427 views

How to set MTU on bridge device with netplan & networkd?

I want to use netplan with the networkd backend to bring up an ethernet bridge, with a specific MTU. I can configure the MTU parameter in the netplan files, for both the bridge device and ethernet ...
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74 views

Will MTU increase affect all parties?

Will a Maximum Transfer Unit (MTU) increase for the ethernet interface on one device, box-a pictured below, in a LAN network also increase the MTU between each of the clients and box-a? Put another ...
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387 views

How MTU set on router affect devices?

This is more a question for clarification then a request for a solution. I've read a lot of questions and answers regarding MTU tweaks on routers and devices but I don't understand what's happening to ...
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1answer
57 views

Why do I see Ethernet frames that exceed the MTU+Ethernet header size?

I have a consumer-grade Wi-Fi router that hosts a local network. The router is connected to the Internet through a campus network (i.e., an Ethernet cable connects the WAN port to a campus Ethernet ...
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33 views

installing mtu and processing pmtu

When working with the GRE tunnel, I encountered a problem. If you let the traffic through the tunnel rt_pmtu be installed in 1476, then I try to lower the Mtu on the GRE tunnel to 1300, but as a ...
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1answer
340 views

Separate MTU for IPv4 and IPv6 on Linux

Is it possible to define MTU on an interface with different values for IPv4 and IPv6 on a Linux machine? It seems that command ifconfig MTU defines the same MTU for both IPv4 and IPv6. Any help is ...
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2answers
753 views

Double NAT MTU setting for the inner network

I have a home network with two routers, one behind another. The outer router's WAN port is a VDSL2 PPPoE connection with a live IP address and the MTU size of 1492. The inner router's WAN port is ...
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1answer
203 views

IPv6 fragmentation not happening

I have set up a test network with 2 Linux PCs working as routers and 2 Linux PCs working as normal clients. The 2 routers are connected to each other and each client is connected to one router. On the ...
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1answer
306 views

VPN slowlyness fixed with MTU, but connection problems to extern networks

I was facing some issues with the VPN Performance of Windows 2012 and Windows 2016 VPN. I was not able to get high data exchange rates. It took minutes to open a 3 MB excel file. I then reduced the ...
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1answer
59 views

mtu of routers bigger than endpoints

we have 30 remote sites, connected thru leased lines. our provider setups the routers , we can only read snmp info. on the routers, most of the ifaces have mtu of 1500, but a few ones have bigger ...
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68 views

Brand-new PC only loads some domains when on Wifi

I have a new Lenovo Carbon X1 4th gen. Wired internet with an adapter works fine, but the wifi won't work. I tried installing the newest drivers, reinstalling windows, and even installing drivers for ...
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1answer
400 views

TCP application setting Don't Fragment (DF) Bit

I noticed that some TCP application is setting the DF (Don't Fragment) bit. My research seems to indicate that TCP wants to avoid fragmentation and instead want to adjust the segment size (MSS). ...
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1answer
92 views

What causes the maximum frame lenght and in consequence the MTU of the different network technologies

The different Maximum Transmission Units - MTU - (on Layer 3) are caused by the different maximum frame sizes (on Layer 2) of the differnt network technologies. Some MTUs: Ethernet: 1500 Bytes PPPoE:...
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519 views

Emulating MTU problems - how can I drop large packets

When I'm out and about with my laptop I use OpenVPN to connect across public WiFi back to my server. Occasionally I come across what I have to assume are MTU issues - large packets get dropped, ...
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1answer
74 views

Bypassing max MTU

I'm considering upgrading my home network to a router with jumbo frame support. Before I drop the cash on it I have a question about MTU's. The largest MTU my current router supports is 1500. On ...
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238 views

Can't find MTU field configuration in my Router settings?

I have a HUMAX router in my house and I'm trying to configure the proper MTU size for my newtwork. The problem is that when i login in the routers admin panel, i can't find the MTU setting. image
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2k views

What MTU size should I use for VPN in the modem router settings

In that TP-Link article its mentioned that http://www.tp-link.us/FAQ-190.html "Due to additional complications, VPNs require a different type of MTU test" I have adsl2+ model router. The MTU size for ...
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647 views

My syslog is full of errors from NetworkManager about setting the MTU for wireless adapter

NetworkManager keeps trying to set the MTU for my wifi connection to 9216 and then complain about it: NetworkManager[9173]: <error> [1469713916.019478] [platform/nm-linux-platform.c:2489] ...
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1answer
198 views

cannot ping using my interfaces MTU

I'm trying to find the best MTU for my network to try and improve my PS4 as it's a bit poor. On my PC, when I run the command: netsh interface ipv4 show subinterfaces It tells me my MTU is 1500. ...
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461 views

TP-LINK wired connection failed on some websites

I have a TP-Link TL-WR841N router and for some reason the wired connection is very slow and is unable to load some website. If I try a traceroute to these sites I get a timeout. When I directly use ...
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584 views

MTU setting in my router

I've reset my router (after changing the home gateway to fully bridged mode) and want to know - can I manually set the MTU in the router to 1500 (and / or play around with smaller values if 1500 doesn'...
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1answer
552 views

Ping requests time out for specific packet sizes

After having VPN problems with my new internet provider on LTE router Huawei B315s-22, found out such interesting behavior: ping bite.lv -f -l 1436 -n 1 -----> Reply from 213.226.139.45: bytes=...
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1answer
2k views

Trying to achieve faster file transfer rates on my home network

I have tried to work through this problem on my own, but I have reached the point where I need your help, and/or encouragement. I have a small home network set up. The main components are 2 Macs ...
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1answer
84 views

Ubuntu 10.04 | Terminal Freezes on certain commands | MTU

Isolated problem: I try to cat /etc/rc.local and I can't do anything in the ssh session after that. I've tried many of the common things, but it seems to freeze on any command, but I can do an ls, w,...
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1answer
355 views

Can a home PPPoE connection access all websites, regardless of the site infrastructure's MTU settings?

I'm just trying to get my head round MTU, MRU and MSS. My interest initially came from the answer in this post: Security risk of PING?: Some ICMP packet types MUST NOT be blocked, in particular ...
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728 views

How to find proper MTU size for FTTH EPON?

I've recently moved to a ISP that provides a 4mbps connection through FTTH(Single OFC). There is a EPON ONU in my premise from which a RJ-45 lan cable is connected to my Intel DH67CL1 board based PC. ...
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1answer
134 views

Do all hosts and nodes in a Broadcast domain have to have the same MTU value?

Some documents on the Internet say that all interfaces in a broadcast domain ( ie Router boundaries ) have to have the same MTU value. Is that an inflexible rule ? But what about my roaming laptop ...
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1answer
310 views

Throughput decreases after MTU 5000

I am trying to test throughput between two computers directly connected through 1 GbE and testing with iperf. I am getting a throughput around 980Mbps when MTU is between 5000 and 5050, however it ...
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2answers
3k views

No computer on network can play YouTube videos

I have a Netgear FVG318v1 router and all computers on the network cannot play any YouTube videos. I have tried with 3 computers, PC and Mac with all different kinds of browsers. All I get from YouTube ...
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2answers
919 views

Drop IP fragments of a certain protocol

When conntrack is active, the iptables stack never sees a fragmented IP packet, only the reassembled one (source), so the -f test never matches. If I want to block any fragment I could set ...
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1answer
9k views

Windows 7 doesn't request MTU from DHCP server; what is it thinking?

My computer's Ethernet adapter uses 1,500 byte Ethernet frames. Normally this means that my Local Area Connection's MTU is 1500 bytes. But my (IPv4) connection to the Internet has some overhead. This ...
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64 views

Set an ipv6-specific MTU

I have a router which has ipv6 connectivity through a tunneling mechanism. The router announces a prefix in the LAN, and clients get native ipv6 connectivity on their point of view. The MTU of the LAN ...
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2answers
766 views

Configure HP iLO MTU Setting - Site is behind several firewalls and MTU requires lowering for access

Just wondering if anyone knows how to adjust the MTU setting for a HP server iLO NIC? The site is behind several firewalls and we have had problems with other things that has required us to lower the ...
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3k views

Changing MTU on Windows 8

have tried several times to change the mtu on my windows 8 hp laptop, have used the method shown here- http://www.richard-slater.co.uk/archives/2009/10/23/change-your-mtu-under-vista-windows-7-or-...
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560 views

Why does postfix take so long time to receive emails from gmail?

How can I manually check for an email from the command line? How can I force postfix to receive/update emails? The email from gmail takes 8 minutes till it will be received by postfix. How can I ...
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71 views

What is the relation between interface MTU and received packets length?

Let's say that two hosts A and B communicate via an Ethernet medium. Host A has MTU 1500 and host B has MTU 1300. If A is sending a packet with length 1500, will host B receive it?
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8k views

how to set MTU value in windows xp

I wish to change the MTU value on my pc (XP) i tried some registry mathods- added some values in several places: (this one is a windows tutorial) HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\...
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1answer
14k views

TP Link wireless router connects but web pages do not load

I have recently purchased a TP-Link TL-WR740N but somehow it is not working properly. I do not have an ISP connection, rather I have fixed IP connectivity so that I get a 100Mbps Ethernet cable ...
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3answers
5k views

How to configure a large mtu (linux)

I have a gigabit ethernet connection from my laptop to my router, and a working ipv6 connection to the internet. I can receive very large packets from sites on the internet, with sizes up to at least ...
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1answer
860 views

Why might my HP C7200 printer appear to have an MTU of 1498?

On my wireless network, I can tracepath to a mac using MTU of 1500 on Ubuntu linux 12.04. (Mac MTU is set to 1470 for some reason, but reply frames are not that big so this does not matter) When I ...
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1answer
2k views

OS X Failure in Path Maximum Transmission Unit (PMTU) Black Hole Router Detection

This all started when I was trying to download a podcast on my Mac. This happens in both Snow Leopard and Lion when the Ethernet interface is set to use Jumbo Frames. prompt> curl -v -o x.mpg ...
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854 views

Unable to remotely connect to a machine after succesfull VPN login

I'm unable to remotely connect to a virtual machine even after successfully logging into VPN through my broadband connection. Weird it is, I'm able to remotely connect to that machine after VPN log in ...
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1answer
1k views

DF bit in Apache to Tomcat communication

Edited (edits are in italics): In my configuration I have an Apache 2.2 Http Server configured as a reverse proxy with mod_proky_jk, that exposes http service from an Apache Tomcat 6 application ...
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3k views

Timeout while testing MTU via ping

I tested it on Windows 7 and Ubuntu 11.10 with MTU size 1500B. IP packet - 20B ICMP packet - 8B 1500 - 28 = 1472 So maximum packet that I could ping without fragmentation is 1472B, and this is ...
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3answers
16k views

Can't access some websites, possible MTU issue on the router?

Two particular sites that I can't access at all is css-tricks.com and jquery.com which are pretty crucial to me since I'm a web designer. I talked with my ISP and we tried Using different browsers,...
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1answer
1k views

What is the most MTU efficient way of creating a network tunnel?

I am currently using SSH tunneling to connect to the internet via a remote computer using the -D ssh argument. I've recently run across a problem with this solution -- the SSH protocol decreases the ...
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1answer
2k views

MTU setting ignored by Java socket on loopback

I've got a mtu problem. I did the following: root@sa-headend:/home/sa# ifconfig lo mtu 1500 root@sa-headend:/home/sa# ifconfig lo lo Link encap:Lokale Schleife inet Adresse:127.0.0....
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3answers
14k views

About MTU settings in machines and switch

Suppose I have two machines and one switch. M1--Switch--M2. The settings are: M1 has MTU set to 100 Switch has MTU set to 1000 M2 has MTU set to 1000. Questions: When M1 tries to send a ...