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0
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0answers
10 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 ...
-3
votes
0answers
28 views

Windows XP - Configure to request DHCP Option 26 to set MTU Size [on hold]

Appears that it may be set here: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Dhcp\Parameters\Options\"Option ID" And I could certainly create the "Option ID" Key named 26 but unsure what to ...
-1
votes
1answer
44 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
votes
0answers
78 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
87 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. ...
0
votes
2answers
183 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
181 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
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0answers
91 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
66 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
39 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
316 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
505 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. ...
0
votes
0answers
51 views

Throughput decreases after MTU 5000

I am trying to test throughput between two computers directly connected through 1 Gb and testing with iperf. I am getting a throughput around 980Mbps when MTU is between 5000 and 5050, however it ...
1
vote
1answer
421 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
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0answers
106 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
81 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
560 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
540 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
74 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
107 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
97 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
369 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
385 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
1k 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
151 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
2k 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
829 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
2k 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
2k 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
160 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
42 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
231 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 ...
17
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2answers
6k 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 ...
0
votes
0answers
515 views

ICMP ping size stops working at 1272 bytes

I am pinging between two servers. These are both connected with 100Mbps ethernet NICs to the same switch. As you can see from the results below, I can ping from one to the other giving an ICMP data ...
13
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
209 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
175 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 ...
3
votes
1answer
1k views

PIX 506E, MTU, VPN Packet Fragmentation and Shoretel IP telephone system

We have two sites, a large Southern site and a small Northern site, that have a VPN between them defined on two Cisco PIX Firewalls. Over this VPN Shoretel IP phone traffic travels as well as all ...
0
votes
0answers
2k views

VPN Issues when uploading files - MTU issue?

I have a PPTP server setup at home, which I connect to from my work's network. I can connect to it without any issue, but when I try to upload files, I lose connectivity to it about 1mb into the ...
4
votes
1answer
516 views

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 ...
2
votes
1answer
747 views

other than manually changing it, how is MTU set?

I recently discovered a Windows 7 client that couldn't connect to one of our servers. It turned out the problem was both that the server was set for an MTU of 1514 and that the client was set to 1504. ...
2
votes
2answers
808 views

Getting interface MTU under Linux with PCAP

I am interested in storing packets I sniff using PCAP. As I preallocate the memory I need - i.e. a multiple of the MTU of the interface I am sniffing from, I would like to discover how much memory I ...
1
vote
1answer
362 views

Setting MTU Per Destination Host

I'd like to change the MTU per host as I have a mixed infrastructure where not all devices support the same MTU. I'm on OS X 10.7 and like to set some MTU per destination host and a default one.
3
votes
4answers
1k views

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: ...
1
vote
2answers
199 views

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: ...
0
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2answers
346 views

Computer Networks bonus: find MTU less than 1500 [closed]

This is a bonus question in my Networks class: I have to find a destination for which the path MTU < 1500 bytes. For example using the command traceroute -F www.uwaterloo.ca 1500 works, and ...
0
votes
1answer
863 views

What is the difference between IP_MTU_DISCOVER values (IP_PMTUDISC_xxx)?

The IP_MTU_DISCOVER description from "man 7 ip" is too short. As far as I understand IP_PMTUDISC_DONT/IP_PMTUDISC_DO values enable/disable packet fragmentation on a route. What are IP_PMTUDISC_WANT ...
1
vote
1answer
702 views

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 ...
3
votes
1answer
2k views

Is there a way of setting an MTU lower for traffic destined to a specific IP address on Cisco ASA?

I have a number of VPN sites where the MTU is lower than standard (1500). I have had at least one site where fragmentation of packets has had an effect on the success of building an IPSEC tunnel. ...
0
votes
1answer
254 views

(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 ...