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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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Path MTU is not always 9000, only in one direction

I have a question about MTU or path MTU. In my setup I have 2 computers (firewall, Windows PC) and one NAS, each with a gigabit interface. They are connected throughout the same gigabit switch. In all of them I configured a MTU of 9000. Also…
Hirsch
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How is the Ethernet payload only max 1500, while I can ping with larger size packet?

Just recently I came to know that the payload of Ethernet is max 1500 bytes (mtu). The first thing that came to my mind was that we can ping with much more size than that. So I thought maybe the ping packet is being fragemented in someway. So I…
AhmedWas
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Ping : How to differentiate between Host powered off and MTU too long?

I changed the eth0 MTU size to 1550(using : ifconfig eth0 mtu 1550) and ran ping -c 1 -M do -s 1500 -w 5 {some other IP} and The output I see is, --- x.x.x.x ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 4001ms The…
PleaseHelp
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Force jumbo packet fragmentation

We are in a cluster environment. We have compute nodes with jumbo packets enabled and a MTU of 9000. We are running into some issues in tracebacks to an address outside of our lan, where jumbo packets are being dropped due a firewall with a standard…
Martin Forde
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dose setting Jumbo frame on linux redhat influencing OS performance?

We set the MTU to 9000 on all our linux machines ( we have redhat machines version - 7.3 ) , linux machines are part of hadoop clusters we want to know if set the MTU to 9000 can be negative on OS performance? Dose set other Jumbo frame value as…
shalom
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linux fine tuning after setting the MTU to jumbo frame

We want to set the MTU to 9000 bytes on our Linux machines (distribution is Redhat 7) In this case, how would I tune the memory page size according to MTU size of 9000 bytes? Also, what are the risks associated with setting the MTU to 9000 Bytes?…
shalom
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MTU issue - Packet loss with certain Destination

A customer is having issue with our system and after investigating and analyzing tcp traffic with tcpdump, I noticed that fragmented packets were not received by our cloud server (OVH). I did some tests: Changed the cloud server address to our old…
JPelletier
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Centos 7 pptpd mtu size

i'm using pptpd on centos7 as PPTP VPN Server how can I change the MTU size on server side cause some users cannot connect to the server thanks
Pedram Masoumi
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Cisco 2960X and Jumbo frames on particular ports

I would like to setup several ports to be able handle jumbo frames. This will be only for my backup nas connected to ESXi host. I did create vlan 103 where I changed mtu size to 9000. Problem is when I want to check accpetation of jumbo frames…
Roman Bielich
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Reassembly fails at destination

Say I have Host1 & 2 connected to a router with different speeds. Host1 <--100 Mbps--> Router <--10 Mbps--> Host2 Host1 sends 10MB of UDP data using nc command to Host2, but the Host2 fails in reassembling fragmented packets and sends…
Jeyaram
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HTTP webserver gateway timeout 504 only from one ISP

I have configured a nginx http webserver to serve a site on CentOS 6 Virtual machine. every things are works fine but when I connect to site from a special ISP, the site wait and after a while respond 504 Gateway timeout. This occurs only from this…
Ghasem Pahlavan
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How to setup linux to retransmit TCP packets by reducing the packet size like OS X

On OS X I noticed that for packets which are not ACKed, the system retransmits them with reduced packet size. This can be seen in the image below. Is it possible to enable the same behavior in Linux systems too?
akshat
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Linux host does not retransmit with a lower packet size in response to ICMPv6 Packet Too Big message

I'm seeing this in Wireshark when curling this URL: On the same network, a Windows host retransmits properly, but an Android host does not. On a different network (presumably appropriately configured), the same Android host works. What could be the…
univerio
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Forcing IP fragmentation and reassembly for some traffic thru a VPN tunnel

Is there a way to force IP packet fragmentation before they go into tun0 and then force reassemble them on the other side of tun device? I have some IPSec traffic that I can not control, and it wants 1500 MTU and just gets dropped at the tun…
grandrew
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Force Windows to send packets as soon as they arrive the nic

I have a network application running on Windows Server 2008 R2, that must send small packets in a very short time interval, each microsecond matters. My problem is that windows accumulates the packets and sends them in a big TCP packet, but I want…
Yekoor
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