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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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How can I set the MTU for just one remote server in Linux?

Hi I have a linux server that is behind a customer firewall. I can SSH into it but when I try to scp, the connection dies. I believe this is an MTU issue as described here: http://www.snailbook.com/faq/mtu-mismatch.auto.html. How can I set the MTU…
MattSmith
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Configure LeftHand iSCSI SAN for jumbo frames after clients are configured

This is similar to enabling jumbo frames on an iSCSI network after the fact but in our case we configured the switches and then went through all the hosts, enabling jumbo frames (we may have screwed ourselves here). The SAN is a Lefthand (actually…
murisonc
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(RFC-791) Application Layer PDU size, guaranteed to pass without fragmentation

I am writing a client-server python application, a part of which is using UDP Multicast to communicate. And my current concern is about fragmentation. RFC 791 (page 24) says: Every internet module must be able to forward a datagram of 68…
athspk
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How do I change the MTU for only localhost connections on a Red Hat box?

I want to change the MTU value for only the connections that are going between localhost / 127.0.0.1 on a Red Hat box. How do I do that?
Manto
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different MTU sizes for bond aliases

I have a bond interface but I want to change the MTU to 1500 only for bond9:22 Is this possible? bond9:22 Link encap:Ethernet HWaddr 00:0E:0C:E4:BE:F9 inet addr:10.7.18.58 Bcast:10.7.18.255 Mask:255.255.255.0 UP BROADCAST…
cateof
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System MTU for SAN switch

I have a SAN with redundant cisco 2960s when I set it up a while ago I set all of the interfaces to use an MTU of 9000. I was looking at the config today and I noticed this line system mtu routing 1500 will that cause any problems? or because this…
Peter
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MTU issue with one site only

I am currently troubleshooting an issue where some users on Windows 7 and XP systems cannot access an SSL website on our network. The same site works fine on our servers (Server 2003, completely up-to-date, and a Ubuntu Server box) and all of our…
Matthew Iselin
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Maximum Transmission Unit of VDSL

A simple question (hopefully) but with no clear answers when doing a Google Search. What is the MTU of VDSL (not VDSL2)? With ADSL it was 1492, but most ISPs added PPPoE/PPPoA headers reducing it to 1452, is this still the same when it comes to…
Metalshark
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What's magical about MTU and packet drops?

With default MTU as shown below: hosta$ ifconfig eth0 | grep mtu eth0: flags=4163 mtu 1500 I can ping from a different server using a 1500 payload hostb$ ping -s 1500 -c 2 hosta PING hosta (hosta) 1500(1528) bytes…
Srikanth
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which Wireguard MTU is chosen when each side has a different MTU value?

tl;dr given a Wireguard client and server with different MTU values, which value is used? Given a Wireguard "client" with configuration file [Interface] MTU = 1440 ... and a Wireguard "server" with configuration file [Interface] MTU =…
JamesThomasMoon
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forwarded TCP traffic is refragmented on Linux despite the "Don't fragment" flag

We have 2 VPN servers at the same hoster. The servers are virtual and they have different Linux distros. The VPN clients establish https connections to the same Amazon EC2 server. The TCP packets from EC2 always have the "Don't fragment" flag…
basin
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PMTUD/ICMP black hole problems across a VXLAN tunnel

I'm running a Proxmox PVE host and am trying to use VXLAN to connect the machines running on it to various networks in our Lab. However, I'm running into weird MTU-related problems that I don't understand. First my setup. The basic layout is that…
Christopher Engelhard
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Increasing MTU size

Why would increasing the VLAN MTU size cause things to break? We have a customer who wants 2000 byte packets for some reason, so I increased all the physical links to 9216, which didn't cause any problems, but it didn't actually allow the 2000 byte…
abatie
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How to setup permanent MTU size in RHEL 7 for eth0 interface?

I am using RHEL 7 and trying to setup permanent MTU size to 8500. Not able to find a way to set it up permanently. The server does not have dhcp.conf file in it. I am using below command for temporary solution. But the MTU size gets reset after…
Piyush Patil
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NFS insists to send packets over MTU, nftables might be the solution

I have an NFS mount over a Strongswan IPSec tunnel, which is encapsulated in a 6to4 tunnel. The IPSec is because I need encryption for NFS traffic, the 6to4 is because the VPS provider won't assign a native IPv6 prefix to my server. Because I had…
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