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1
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1answer
22 views

Does TCP's MSS hide a mismatched intra-LAN MTU?

I'm trying to understand how mismatched MTUs behave in a network. Suppose two hosts are able to talk to each other through an Ethernet-based network. The network and host A are configured for jumbo ...
1
vote
1answer
79 views

Can't SSH to any servers

It's for a day that I can't login through SSH to my servers. Using both Putty and MobaXterm. MobaXterm ends with: debug1: sending SSH2_MSG_KEX_ECDH_INIT debug1: expecting SSH2_MSG_KEX_ECDH_REPLY Read ...
0
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0answers
43 views

how to change MTU inside docker container which is running with ubuntu 14.04 and also on host machine with ubuntu 14.04?

I want to change MTU(Maximum Transmission Unit) inside docker which is running on ubuntu 14.04. also docker container running with ubuntu 14.04. The problem is that its docker0 interface on host os ...
0
votes
1answer
49 views

Fragmented DNS Packet

The DNS response against my domain is 1228 bytes long and I need the packet to get fragmented in 3 packets. To achieve this I have set the MTU at name server (bind9 running on the machine) to be 500. ...
0
votes
1answer
61 views

Linux route cache seems to load outdated settings

On SLES 11 SP3 (Kernel 3.0.101-0.46) I see the following route behavior: When I set a route specific MTU once via ip route change ... mtu lock 1500, everything works as expected (setting an MTU of ...
4
votes
2answers
224 views

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 ...
6
votes
2answers
2k views

MTU on server accidentally set to 0, can't ssh into it?

My server had some problem with the ssh and I couldn't upload files of size > 10 KB, as scp would hang during the copy. I found a solution for this problem here, and I was changing the MTU, when I ...
1
vote
0answers
88 views

Can't mount read-write iSCSI with MTU=9000

I'm attempting to connect my desktop (running debian 7) to a QNAP NAS (running QTS 4.1.1) using iSCSI with an MTU=9000. The network infrastructure consists of a cat5e crossover cable between the ...
0
votes
1answer
101 views

IPsec transport mode and MTU

[Similar to Right way to set the MTU of an IPsec Client (Linux/Racoon), but different in that there is no router on the responder side] I have a setup where machines in a local network need to talk ...
0
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0answers
129 views

Right way to set the MTU of an IPsec Client ( Linux/Racoon)

Here's the network topology : (PC1:IPsec Client)eth0---Internet CPE---((Internet))---Internet CPE---(PC2:IPsec Server) I've set up an IPsec Internet Gateway : PC1 sends all traffic, encrypted in an ...
5
votes
1answer
444 views

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' }) ...
0
votes
1answer
315 views

CentOS 7 MTU setting not works

I am using CentOS 7 to test some network performance. The interface setting is normal like that : saberin@localhost ~]$ ifconfig enp0s25: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 ...
5
votes
1answer
146 views

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: ...
8
votes
1answer
213 views

Does setting MTU on logical interfaces affect physical interfaces

I've been using a combination of interface bond-, vlan- and bridge-interfaces to provide redundancy and different logical network layers to xen domU's. This setup is working well however i'm a bit ...
1
vote
1answer
276 views

Debian don't forward through L2TPv3 more than mtu l2tp virtual interface

R3--R1--Internet--R90 R3: ip addr 10.123.0.3 R1: sudo ip l2tp add tunnel tunnel_id 699 peer_tunnel_id 699 encap udp local 5.254.174.8 remote 5.254.174.90 udp_sport 699 udp_dport 699 sudo ip l2tp add ...
3
votes
2answers
2k views

OpenVPN: How to mitigate path MTU issues on a per-client basis?

We have dozens of embedded devices installed at customers, all calling home to our OpenVPN service. That works fine in general, but a few of our customers have severe path MTU issues. Our influence on ...
0
votes
0answers
140 views

Pptp Vpn: buffering packet .. (expecting .., lost or reordered)

System log is full of such messages. AFAIK this can be related to MTU size. ppp0 negotiates a MTU of 1396 with the ISP. I've tried so far: ip link set dev .. mtu 1396 iptables -A FORWARD -i ...
-1
votes
1answer
209 views

VMWare - Jumbo Frames over iSCSI to a NAS4Free array

I am having problems getting Jumbo Frames working over my iSCSI connection. Here is what I try. 4 1GbE connections on 4 different subnets on my NAS4Free array for iSCSI, MTU set at 9000 2 redunant ...
0
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0answers
134 views

xen routed networking maximum segment size

For a few days now we experience issues with xen in routed networking mode regarding the MTU and MSS values (xen 4.1, debian wheezy, ISP is Hetzner) (network-script 'network-route netdev=eth0') ...
-1
votes
1answer
214 views

windows update error 80072ee2 caused by linux router, possible mtu issue? [closed]

For a few days now, the Windows 7 workstations on my network have been unable to connect to Windows Update. They are getting the infamous error 80072ee2. They are connected to a simple SOHO switch. ...
1
vote
2answers
3k views

Permanently set MTU on Ubuntu 14.04 machine within an Amazon VPC

I have some Ubuntu 14.04 machines running in an Amazon VPC. When they start, they have an MTU of 9001, but this appears to cause some problems when communicating with other servers which have an MTU ...
0
votes
2answers
1k views

MTU between Juniper and Cisco, cause of packet loss?

This office has a network consisting of Cisco Catalyst and Juniper EX L3 switch. Cisco Router and Juniper L3 switch share a OSPF area in between them. Hosts on Juniper side are running FTP servers ...
2
votes
1answer
709 views

Full MTU not utilized with jumbo frames enabled

I've been testing to see if I can get any benefit from enabling jumbo frames. I've set up two identical Dell R210 servers with Xeon quad core E3122 CPUs, 8G of RAM and Broadcom NetXtreme II BCM5716 ...
1
vote
2answers
143 views

CentOS ssh connection stalls after server bandwidth upgrade

I have a few linux servers inside a customer that recently MASSIVELY increased his bandwidth - from about 0.8/5mbps to 25mpbs/100mbps... (yes 100mpbs!) this is very good, but ever since my ...
1
vote
0answers
95 views

MTU on mobile data networks

I found various lists of MTUs for different links, but they never contain UMTS, LTE, EDGE, HSPA, GPRS. What are the MTUs of the above mentioned technologies?
1
vote
2answers
2k views

XenServer 6.2 changing mtu

So I've looked around for a way to change the MTU of interfaces on XenServer 6.2, but can't find anything that works for me ... One method spoke about changing the ifcnfg-intX files in the ...
4
votes
1answer
3k views

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. ...
1
vote
1answer
1k views

Cisco IPSEC VPN Slow Speeds

We have a site to site IPSEC VPN, both endpoints are Cisco PIX 515e's. The links at both end are 100mb, however speeds over the VPN (logged using jperf) are at most 4mb. Obviously this represents a ...
0
votes
0answers
142 views

Severe performance issues sharing openvpn client connection to LAN clients virtualbox

I am trying to set up an internal network in Virtualbox in order to share an openvpn client tunnel with multiple VMs acting as clients that should be completely isolated from everything except for the ...
2
votes
1answer
116 views

Maximum MTU size

Thought one of the issues I'm experiencing with the following question is due to MTU rightfully so. ESXi 5 VM Putty session hangs, vSphere client timing out However, when I tried testing the ...
1
vote
1answer
2k views

How do I view cached PMTU under Linux (and all other OSs)

When I ping a remote site with the DF bit set and a packet size that is too big for my router the first ICMP "fragmentation required" message is sent from the router. After that the message comes from ...
2
votes
2answers
1k views

SFTP fails on listing directories with large number of files

I try to connect to an sftp server (vsftpd) on Centos server through port 22. there is no problem in connection and initial directory listing; there is also no problem if I click on a directory with ...
-4
votes
1answer
106 views

How to maximize mtu size for SunOS 5.10 Generic_147440-26 sun4v sparc sun4v [closed]

Despite installing and enabling the 10G fiber card, data copy or transfer is still happening on a 1G rate.
2
votes
1answer
203 views

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 ...
1
vote
1answer
126 views

How do I force a specific MTU for only certain TCP ports?

Background I have a set of embedded hardware deployed in the field. These remote machines connect back to my servers at AWS running Ubuntu and I use the iptables mangle chain to lower the MTU to 500 ...
1
vote
3answers
520 views

disadvantages MTU over 1500

What disadvantages have to set the MTU to the maximum possible value in ALL network adapters on a network (including virtual switches vmware esx)? Why do not the producers as a default? I do not ...
0
votes
1answer
770 views

What is the right way to temporarily disable/enable PMTU Discovery on a Linux box?

I've a few pcaps that contain packets larger than standard ethernet MTU size of 1500B. I searched about this and found refs pointing towards Jumbo Frames. I now understand that since I'm on a GBE ...
1
vote
4answers
2k views

Smaller network packets vs bigger packets - confused

Some are saying that bigger packets are better to send then smaller. But in this app: http://media.pearsoncmg.com/aw/aw_kurose_network_2/applets/message/messagesegmentation.html The lower the packet ...
0
votes
1answer
223 views

Jumbo Frame configuration & VMware

I am hoping one of you can help clear up some of my confusion on this matter. We have 2 new catalyst 3750 switches to support our VM hosts and SAN arrays. The SAN arrays utilize jumbo frames with an ...
6
votes
1answer
4k views

How do I prevent TCP connection freezes over an OpenVPN network?

New details added at the end of this question; it's possible that I'm zeroing in on the cause. I have a UDP OpenVPN-based VPN set up in tap mode (I need tap because I need the VPN to pass multicast ...
0
votes
1answer
1k views

openvpn TCP/UDP slow SSH/SMB performance

I have question about strange behavior of my openVPN configuration on Debian lenny. I have 2 server configs (one proto tcp-server based and one proto udp based). ISP bandwidth is 7Mbit/7Mbit. When I ...
8
votes
2answers
3k views

Jumbo frames between KVM guest and host?

I am trying to implement a 9000 byte MTU for storage communication between KVM guests and the host system. The host has a bridge (br1) with a 9000 byte MTU: host# ip link show br1 8: br1: ...
1
vote
1answer
3k views

Linux - set an interface to not fragment packets

I am using a Linux as a router. The machine has two NICs. This router will be used for experiments, so I have set one of it's interfaces to have a MTU that is lower than the standard (let's decide ...
-1
votes
1answer
175 views

centos 5.6, virtual on Vsphere

suddenly my virtual centos server (5.6 on VMWare-VSphere) is not working... It started with the url not responding, nor the ip. (NO HTTP response, no ping). When I entered on the server via ssh to ...
0
votes
1answer
46 views

Finding network type using MTU

For example MTU of Ethernet is 1500. Now if the packets are fragmented, then observed MTU will be the MTU of the router (i.e. less than 1500). Is there any method to find out the type of the client ...
2
votes
1answer
279 views

MTU value causing applications to hang

I am using CentOS 5 in my environment and it acts as a gateway for my LAN. My eth0 interface MTU is set to 1500 (default). UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Recently I am facing a ...
18
votes
2answers
10k views

What is the “in-the-wire” size of a ethernet frame? 1518 or 1542?

According to the table here, it says that MTU = 1500 bytes and that the payload part is 1500 - 42 bytes or 1458 bytes (<- this is actually wrong!). Now on top of that you have to add IPv4 and UDP ...
14
votes
1answer
2k views

What am I misunderstanding about calculating MTU?

Okay, I just finished resolving a jumbo frames issue between a few Xserves, a Netgear GSM7224, and a Drobo B800i. It turned out that the Xserves (Mac OS X 10.6.8 Server) and the Drobo B800i accept the ...
4
votes
2answers
259 views

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 ...
2
votes
1answer
212 views

Can fragments of a packet be refragmented again?

In IPv4, fragmentation is done by routers on way to the destination if DF(do not fragment) flag is not set in the IP packet. Once a packet is fragmented, its fragments may take different paths (due ...