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Questions tagged [mtu]

"Maximum Transmission Unit" (MTU) is the maximum number of bytes a frame or packet may have on a network (in several layers of the OSI model). Wrong MTU can lead to packet loss.

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Relationship between MTU and NFS rsize/wsize options

I'm trying to understand networking settings related to NFS and various buffer sizes (and there are quite a few). I'm running wireshark and inspecting the TCP packets arriving at the NFS server. Wireshark is showing a packet size max 32626 during an…
Jmoney38
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How to increase MTU size on Linux 2.6?

How to increase MTU size on Linux 2.6? Is such a thing possible? If yes, which files (in /etc or elsewhere) must one edit?
NeoCoder22
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What's the best MTU setting for a web server?

I manage several web servers and their MTU settings were set at 1500 by default. Some of the machines have an MTU setting of 576. I've read a bunch about MTU and I feel I understand it well enough but I don't have a good sense for the current state…
recursivevirus
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Is there such a thing as a "typical" or "de facto" default for MTU size?

When writing networking software, is there a default, typical, or otherwise de facto standard for MTU size, of which I should be aware? If so, what is it? Is an MTU size of 1500 (as suggested here: What is the Maximum MTU supported in DSL…
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OpenVPN over TCP, terrible latency but only on Win7 x64

I know TCP encapsulated over TCP is a terrible idea in general, but I can deal with the occasional decreased performance and MTU issues, and the snowball effect TCP within TCP provides where error control kicks in on both layers. The latest OpenVPN…
mr_daemon
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Set MTU of interface via powershell

I'm trying to set the MTU for a physical interface programmatically on Windows 7: PS> (Get-WmiObject -Class Win32_NetworkAdapterConfiguration | Where { $_.Description -match '^Red Hat.*#2' }) DHCPEnabled : False IPAddress : {10.10.8.3,…
MikeyB
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POST of MTU + ~798 bytes gets lost

I have a very weird issue with certain packets not arriving on the destination host. It happens when we transmit a POST that is somewhat larger than the MTU. We can reproduce it with this script: #!/usr/bin/python import urllib2 magic_length =…
Halfgaar
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What's going on with this strange MTU?

I have a server mike at our office communicating with a remote server through a VPN. There have been various problems which seem to be linked to the MTU size. Mike is a RHEL 3 server and the customer server is CentOS 5. I used the tracepath tool to…
mmcg
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What is the Maximum MTU supported in DSL Standards

Do any of the ITU DSL standards limit the maximum MTU that can be supported? I know that RFC2516 (PPPoE) limits the MTU to 1492 bytes; however when PPPoE is not used this limit should not exist. The PPP, L2TP and ATM AAL5 standards all have 16-bit…
Russell Heilling
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Slower performance using Jumbo Frames on Dell PowerVault MD3200i

We have a Dell PowerVault MD3200i connected to a server via iSCSI using 2 Dell switches (PowerConnect 6224) at 1GB. The server has VMware ESXi 6.5 installed and it's connected to the PowerVault using 2x 1GB NICs connected to each switch. I have a…
Alberto Medina
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ADSL router happily accepts IPv6 packets of 2K in size

As I understand IPv6 fragmentation, the routers do not perform fragmentation, only the end-to-end nodes do. And when any router along the path receives a packet larger than the MTU of the link to its next hop, it'll discard it and reply to the…
Mansour
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IPv6: using a link mtu greater than the mtu of the default route

When configuring an IPv6 LAN it may be desirable to use router advertisements to announce a link MTU of either the standard 1500 bytes or something larger to enable usage of jumbo frames, perhaps 9000. This will allow communication between hosts on…
Jonathan Swinney
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What IP MTU sizes are seen in real networks

I am writing an application which will be deployed in third party networks. It will receive IP packets and I want to know what the maximum size in reality they are likely to be is. I'm not asking what the Maximum theoretical size is but rather what…
Howard May
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Impact of MTU on IP packet fragmentation and reassembly

Let's say computer S (sender) sends some IP packets to computer R (receiver). Between S and R, there are 6 networks, divided by 5 routers. So the IP packets leave R, go through network 1, pass router 1, go through network 2, pass router 2, etc,…
alejandro
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Understanding Ethernet Headers, What MTU Do I Need?

I see many articles on line stating that the overhead of Ethernet is 18 bytes (example: http://www.learnios.com/viewtopic.php?f=8&t=18887) Looking at this wiki article (http://en.wikipedia.org/wiki/Ethernet_frame#Structure) 18 bytes is the following…
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