If MTU size will increase in cisco 3550 does it will impact any traffic ?

For WiFi traffic from source to destination MTU size should ping up to 1472 Now the MTU is pinging up to 1468 because port level MTU size is 1500 we need to increase 1522.
while we changing size it will impact my traffic ?
Model number: WS-C3550-24-DC-SMI
#sh version
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(25)SEE4, RELEASE SOFTWARE (fc1).
Any suggestions on this.
Thanks in advance.
NagaPrasad

Hello Prasad,
Changing the MTU size in general will not cause any impact except if it is VPC domain.
But it is advisible that MTU size keep same at both ends.
FYI...
Changing the MTU value (with the mtu interface configuration command) can affect the IP MTU value. If the current IP MTU value is the same as the MTU value, and you change the MTU value, the IP MTU value will be modified automatically to match the new MTU. However, the reverse is not true; changing the IP MTU value has no effect on the value for the mtu command.
Please rate the helpfull posts.
Regards,
Naidu.

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Try the standard fixes to rule out a software problem:
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Reset iPod touch: Hold down the On/Off button and the Home button at the same time for at
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Wifi traffic MTU size

For WiFi traffic from source to destination MTU size should ping up to 1472 Now the MTU is pinging up to 1468 because port level MTU size is 1500 we need to increase 1522.
while we changing size it will impact my traffic ?
Model number: WS-C3550-24-DC-SMI
#sh version
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(25)SEE4, RELEASE SOFTWARE (fc1).
Any suggestions on this.
Thanks in advance.
NagaPrasad

Hello Prasad,
Changing the MTU size in general will not cause any impact except if it is VPC domain.
But it is advisible that MTU size keep same at both ends.
FYI...
Changing the MTU value (with the mtu interface configuration command) can affect the IP MTU value. If the current IP MTU value is the same as the MTU value, and you change the MTU value, the IP MTU value will be modified automatically to match the new MTU. However, the reverse is not true; changing the IP MTU value has no effect on the value for the mtu command.
Please rate the helpfull posts.
Regards,
Naidu.

Cisco 3560G and max MTU Size

Hello
I have an Cisco 3560G with an version 15.0(1)SE2 IOS. I want to forward Jumbo frames (ISCSI packets) through this switch.
On my SAN, each interface have been configured on 9000 bytes.
On this switch, I have this output :
Sw1#sh system mtu
System MTU size is 1500 bytes
System Jumbo MTU size is 9000 bytes
System Alternate MTU size is 1500 bytes
Routing MTU size is 1500 bytes
Sw1#
I would like to know how to increase, if possible, the Jumbo MTU to 9198 bytes. I want to do that because the 9000 bytes ISCSI packets normally will been encapsuled using vlan so the ethernet packet will increase to 9022 (Ethernet 18bytes and extra 4 bytes for vlan).
If the Jumbo MTU reconfiguration is not possible, the ISCSI packets will be fragmented each time it forwarded through the switch isn't it ??
Thanks in advance for your help.
Have a nice day
Matt

Hi Bilal
Thanks for your reply.
In the document, Cisco add note on the top of the webpage on the Components Used : "Note: In all the examples in this document, unless specifically mentioned, all values that quote MTU in bytes omit the 18 bytes for the Ethernet header and Frame Check Sequence (FCS)."
So In my mind, the 3560G switch will not drop 9018 ethernet bytes but will normally drop the vlan Jumbo frames (9022 ethernet bytes).
I think Cisco will included the Ethernet header and FCS on the document because networks admins included it and not think to on payload data.
Matt

System MTU size on Cisco switch

after setting sys mtu to something other than 1500 on a WS-C3750G-24TS-1U it appears that this setting will stay in effect even if the startup config is erased and the switch is reloaded. My question is. Does this mean that if I need to replace the switch and I just load a saved version of the config and the vlan.dat files. Most likley if I am running a non default MTU this will not be in effect on the new switch.

Hi IP,
if i was understood properly, you have changed the MTU size of cisco 3750 from default 1500 bytes to 1998(eg.) now even after restarting the switch, this MTU size doesn't come to the default value of 1500 bytes & also when you tried put this config & vlan.dat file you wanted to know whether this changed MTU value will be in effect. Answer is NO, bcoz config & vlan.dat doesn't contain this MTU settings. but you can again manually change the MTU size to 1500 bytes & restart the switch.
hope this helps.
rate this post if it is been clarified.

How do you change the MTU size in a Cisco 871?

This 871 is at a remote site and is an ezvpn IPsec client (network extension mode) back to a 3030 headend.
We're having problems with a PC trying to connect through the IPsec tunnel and we think it may be an MTU size problem.
Int F4 is the outside interface.
We are using a virtual-template associated with the crypto ipsec client ezvpn statement.
When I go into any of the 871 interfaces and type 'mtu 1370' it errors out with 'The F4 (or whatever interface) does not allow manual MTU size configuration.
If I type 'ip mtu 1370' on F4 (or vlan1 or virtual-template 1) this is accepted, but when I do a 'show int f 4', it still shows MTU of 1514 - even after a reload.
What is the correct way to set the MTU size in the 871 router - and is it best set on the F4 interface, the vlan, or the virtual-template interface?

Hi
As per the supporting doc Cisco 871 has one want ethernet interface and 2 switch ports.
I feel you are trying to change the mtu under the switch port which may not be possible.
You can refer the below link for more info..
http://www.cisco.com/en/US/products/hw/routers/ps380/products_data_sheet0900aecd8028a976.html
regds

Will the database size be increased ?

HI All,
I like to ask, will the datafile size be increase, if we put our tablespace in backup mode and forget to put in back in end backup mode.
According to me not, because all the transaction activity will be carried out into redologs and of course, there will be significant increase in redologs. Please correct me, If I am wrong.
hare krishna
Alok

The size of datafile itself will not be affected, but as you mentioned, the amount of redo that you generate will increase.

PDF Size will increase in size dramatically with every submit.

I have a PDF Form desinged using Adobe LiveCycle Desinger ES2.
It has a submit button which will submit the form to the server (IIS and ASP.NET) using this javascript command:
event.target.submitForm( {cURL: "http://server/ASPNETWebPage.ASPX", aPackets:["datasets","pdf"], cSubmitAs: "XDP"});
On the server, from ASP.NET, I use the following code to extract the submitted "chunk" element and convert it from Base64 to Binary PDF File:
            fs = New System.IO.FileStream(mFormFileNameFolder, IO.FileMode.Create)
            bw = New System.IO.BinaryWriter(fs)
            ' Get chunk element form the submitted XML
            Dim srChunk As New StringReader(mXML.GetElementsByTagName("chunk")(0).InnerXml)
            Do While True
                Dim theChunkLine As String
                theChunkLine = srChunk.ReadLine
                If Not String.IsNullOrEmpty(theChunkLine) Then
                    theReadBytes = theChunkLine.Length
                Else
                    theReadBytes = 0
                    Exit Do
                End If
                Dim theBase64Length = (theReadBytes * 3 / 4)
                Dim buffer() As Byte
                buffer = Convert.FromBase64String(theChunkLine)
                bw.Write(buffer)
            Loop
            bw.Close()
            bw = Nothing
            fs.Close()
            fs = Nothing
The above code is working fine, and PDF is generted successfully.
I have one problem.
With every submit, the generated PDF Size will increase dramatically. I reported this to Adobe Support, and they cofirmed that this is by desing and that with every submit, the previous PDF State is saved, and the new state is added. That is why I get huge PDF File.
I was told that the only way to solve this problem is to submit the form as PDF ONLY, and after I save the PDF File on a file system, I then must use Adobe Service/Process "exportData" to extract the XML Data from the PDF.
I think this is really big change to me. I was hoping that there is a way to indentify the latest PDF State from the chunk element.
Any help will be greatly appreciated.
Tarek.

Thanks a lot C. Myers,
You explanation helped me understand what is happening.
I have been following the same method for the past 4 years, and I was hit by this problem (OutOfMemoryException) only when some users started using image size more than 500KB. Then, I decided to report this problem.
I was able to rewrite the code to convert from Base64 to binary using buffering:
http://forums.asp.net/t/1662571.aspx/1?URGENT+Exception+OutOfMemoryException+thrown+when+w hen+converting+to+String+
So far, I am not getting OutOfMemoryExceptions, but the PDF Size will continue to grow with every submit. However, if the all the images size is less than 50KB, the increase is not significant.
Please allow me to ask this question:
Is there a way to change the above code so that I can extract only the last version of the submitted PDF from the Data Stream "chunk" element ?
Sooner or later, some one will notice that such PDF sizes are not logical. Even when the PDF does not have images, I have noticed in the past, some PDF Sizes (for Staff Profile Data Collection Form) are something like 15MB !!! I was not able to figure out why. But now I understand. I think the user must have submitted the form for saving many times.
Now, things are OK. But, I will post back if this problem will fire back.
Tarek.

MTU Size Issue on Cisco 3560 Switch

Could anybody tell me how to change MTU Size on a Cisco 3560 Switch.i mean to say whether it is to be changed on FastEthernet Interfaces or on VLAN 1 or on Global Configuration Mode and with which Command to change it.

I am using MPLS on my Routers and the MTU size i have set on my Router Interfaces is 1524.
When i do a normal ping from Customer's one site to another (where my Traffic has to pass through this Switch VLAN)i get a reply , but when a Ping with a Byte Size of 1500 or more the Packets get completely dropped.
I think due to MTU Mistach bet. Switch and Router the Packets r getting droped,that is why i was trying to change it.
could the Packets get dropped because of this reason.Please suggest.

EIGRP MTU Size Causing Neighbor Flap - Pls help!

I've been reading the post here which is quite good but, I have some outstanding questions I hope someone can help me with?
https://learningnetwork.cisco.com/thread/43100#233367
Essentially, we have a DCI which is an evpl link - layer 2. The evpl connection is terminated with a Cisco 3925 at each location (once it comes out of the provider's Ciena box). It is a dot1g tagged trunk - L2 connection. We are running EIGRP between the two. Before setting up OTV, all link sizes were 1500 MTU...which obviously will not work with OTV....and it didnt!. OTV is running on 7Ks a few hops away from each 3925. So, I went on each and every link - (pain stakingly) and configured MTU size for 9216 - enabling jumboframes at the system level too where applicable. What do you know, OTV started working and i could ping to at least up to 2000 bytes with DF-bit set too! (I didn't try any higher).
Last night, our provider did some 'maintenance' without telling us - which brought the link down. The link was 'down' even after the maintenace was completed. After looking in the logs and seeing this, I suspected it had to do with MTU sizes after quickly googling around.
May 13 12:33:13.698: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is down: Interface PEER-TERMINATION received
May 13 12:33:13.976: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is up: new adjacency
May 13 12:33:24.266: %SYS-5-CONFIG_I: Configured from console by izzi on vty0 (10.241.6.12)
May 13 12:34:00.286: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is down: Interface PEER-TERMINATION received
May 13 12:34:00.616: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is up: new adjacency
May 13 12:34:46.922: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is down: Interface PEER-TERMINATION received
May 13 12:34:47.280: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is up: new adjacency
May 13 12:35:37.364: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is down: holding time expired
May 13 12:37:29.725: %SYS-5-CONFIG_I: Configured from console by izzi on vty0 (10.241.6.12)
May 13 12:37:47.430: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is up: new adjacency
May 13 12:39:01.508: %SYS-5-CONFIG_I: Configured from console by izzi on vty0 (10.241.6.12)
May 13 12:39:11.943: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is down: Interface PEER-TERMINATION received
May 13 12:39:13.973: %DUAL-5-NBRCHANGE: EIGRP-IPv4 10: Neighbor 198.28.132.30 (GigabitEthernet0/0.2) is up: new adjacency
So, I reduced the MTU size back to 1500 and low and behold, adjacency stayed. Let me also say that there weren't any errors on the links too. So, I decided to try and increase the MTU back up to 9216 - OTV started working again and adjancey held - it didnt flap. I thought for a second and decided to bounce the link. Once i did this, EIGRP started flapping again with the same exact behavior. After calling the provider, they claim that their max MTU is only 1522 for our EVPL link. I don't see this being possible since I was able to ping DF-BIT set way above 1522. Maybe I'm missing something. We are going to coordinate with them to increase the MTU size on the link. But why/how did it work to begin with - especially since OTV doesn't support fragmenation....I understand that OTV adjacency can still form since ISIS only needs 14xx something...but I wasn't able to get certain protocals/services like esxi host management to work via OTV until i increased MTU size.
Also, after reading the above article it sounds like EIGRP will 'peer' or decide on MTU of it's update packets? If that's the case, maybe the bouncing of the link allowed EIGRP to negotiate it's packet sizes to above 1500 and that's why if I change the MTU size to above 1500 everything works fine - OTV/2000 byte bf-bit set ping, until I bounce the link? If this is the case, is there anyway to 'force' EIGRP to use 1500 for it's packets for its protocol traffic and allow everything else to use the MTU set on the link?
I would appreciate any help explaining this - hopefully you're not as confused as I was after reading it again!

Did you ever find the root cause and this solution for this? We are experiencing the same issues with our 2 4500 Catalyst and a couple of routers on our inter routing VLAN that we use for only the 2 chassis and a couple of router. MTU is already set at 1500 on the 2 chassis.
005326: Jan 19 11:30:02: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.21 (Vlan990) is down: Peer goodbye received
005327: Jan 19 11:30:05: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.1 (Vlan990) is up: new adjacency
005328: Jan 19 11:30:05: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.21 (Vlan990) is up: new adjacency
005329: Jan 19 11:30:07: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.12 (Vlan990) is down: holding time expired
005330: Jan 19 11:30:27: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.21 (Vlan990) is down: Peer goodbye received
005331: Jan 19 11:30:28: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.11 (Vlan990) is down: Peer goodbye received
005332: Jan 19 11:30:28: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.1 (Vlan990) is down: Peer goodbye received
005333: Jan 19 11:30:30: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.12 (Vlan990) is up: new adjacency
005334: Jan 19 11:30:30: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.11 (Vlan990) is up: new adjacency
005335: Jan 19 11:30:30: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.1 (Vlan990) is up: new adjacency
005336: Jan 19 11:30:32: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 65001: Neighbor 10.190.254.21 (Vlan990) is up: new adjacency

VPN MTU Size

Get this same problem with any Cisco router site-site VPN. Have various customers with 857, 877, 1841, 2811 routers, same problem every time. I'm setting up a VPN with the SDM, link goes up ok, but traffic seems oddly sluggish.
Installing the Cisco VPN client on all PCs seems to resolve the problem - I'm guessing because it sets the MTU size to 1300 - but you always get this error message when testing the VPN from the SDM:
Failure Reason(s)
A ping with data size of this VPN interface MTU size and 'Do not Fragment' bit set to the other end VPN device is failing. This may happen if there is a lesser MTU network which drops the 'Do not fragment' packets.
Recommended Action(s)
1)Contact your ISP/Administrator to resolve this issue. 2)Issue the command 'crypto ipsec df-bit clear' under the VPN interface to avoid packets drop due to fragmentation.
The crypto command doesn't make any difference.
Any ideas gratefully received.

I see the same problem - I have a VPN configured across the Internet between a Cisco 2811 router to a Checkpoint firewall.
Lowering the MTU size on the clients to below the usual 1500 bytes (to below 1300 as specified above) and traffic flows without problem across the VPN. It seems the additional header when going through the tunnel is causing problems.
Is reducing the MTU size on the router interface a possibility? This may cause increased overhead to the router as it has to fragment each packet, and I understand some firewalls may not even allow fragmented packets through. However, changing settings on users desktops / servers is not very scalable, and there will come a time when this isn't possible (old printers??). Is there any specific configuration advice that can be recommended?

Mid 2010 Macbook Pro - Change MTU size kills internet (Jumbo Frames)

Hi everyone, i'm hoping someone here can enlighten or help me solve my problem I'm having.
I am trying to change my MTU size to enable Jumbo frames on my 13 inch Mid 2010 Macbook Pro. I recently bought a ReadyNAS Ultra and would like to speed up transfers to the unit.
My setup is as follows:
I have my ReadyNAS Ultra 2 and 2010 Macbook Pro (Core 2 Duo) wired via cat6 ethernet to my 5th Generation Apple Airport Extreme. The Airport Extreme is connected via cat5e to my AT&T Uverse Gateway which is set up to allow my Airport to assign DHCP and NAT (gateway is in bridge mode with wireless off).
Anyways, I have enabled Jumbo frames on my ReadyNAS, when I enable them on my MBP.. it applies fine. It disconnects / reconnects the ethernet like it should, but then my connection drops. I can't see any devices on my LAN and I cannot access any internet websites, but according to the network pane I am still assigned a valid dhcp address. When I manually try to increase my MTU size, the same thing happens (from 9000 to 1600 I tried every size).....
Could it be my MBP just can't suppose the increase of MTU size? It leaves them at 1500 when I set it to automatic... if it doesn't support the increased MTU size, why would it let me custom change the MTU and even give an option to select "Jumbo Frames (9000)"?
I appreciate any help in advance!!

asdftroy wrote:
If you did read my post then you would have saw that the option is there, but that is not entirely what my inquiry is about. The option isn't working as intended, and I was wondering if anyone had the same issues as me. Thanks anyways.
Anyone else?
The way you responded to someone trying to help you probably means others will be hesitant to try.

MDS Time Delivery Queue size is increasing

Hello Everyone
We are using ICM 8.5.3 , I am getting this message in Event Viewer of Rogger A & Rogger B servers.
Computer:      LHRRGRA.ef.UCCE
Description:
MDS Time Delivery Queue size is increasing, current size is 5525, but will continue to send messages.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
    <Provider Name="Cisco Systems, Inc. ICM" />
    <EventID Qualifiers="41220">32810</EventID>
    <Level>3</Level>
    <Task>4</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2012-06-08T06:12:08.000000000Z" />
    <EventRecordID>127461</EventRecordID>
    <Channel>Application</Channel>
    <Computer>LHRRGRA.ef.UCCE</Computer>
    <Security />
</System>
<EventData>
    <Data>5525</Data>
    <Binary>06010000000000003D9030012A8004A160975AA23D45CD0114000000010041006D6473004C485243444352475241003535323500</Binary>
</EventData>
</Event>
Anyone knowns why getting this.
Regards
Irfan Tariq

The MDS processes on these Routers are unable to communicate quickly enough over their private connection.
You''ll want to check the network connectivity, QoS configuration, link speed, congestion, .... Also be sure to follow this document letter by letter :
http://docwiki.cisco.com/wiki/Contact_Center_Networking:_Offload,_Receive_Side_Scaling_and_Chimney
Cheers,
Kris

6506 - SUP720-3B MTU size

Due to MPLS environment on our WAN, we need to increase MTU size on the lan.
We configure 6500 to use only layer 2 interfaces (switchport activate on each interface)
Do i need to configure MTU size on each interface (i think i need to do it if i want to use this interface at layer 3) or can i configure only global MTU (system jumbomtu 9216)
Is there a command to verify jumbomtu size set on the switch ?

you can use the MTU per VLAN on the 6500.
'set vlan 10 mtu "576-18190"' (catOS)
or
'vlan 10'
'mtu "1500-18190"' (IOS)
this command sets the MTU for VLAN 10; values are from 576 to 18190.
please see the following link for more info: (IOS)
http://www.cisco.com/en/US/products/hw/switches/ps708/products_command_reference_chapter09186a00801eaeec.html#wp1011172
please see the following link for more info: (catOS)
http://www.cisco.com/en/US/products/hw/switches/ps708/products_command_reference_chapter09186a00802debd1.html#wp1027906

Vm-fex mtu size

Hello,
I need to configure mtu 9000 on dynamic vnics (vm-fex vnics).
But I have not found any guide on how to do it. I followed the vm-fex config guide for KVM, but in dynamic vnic connection policy I have not found any parameter to change the mtu size. By default all dynamic vnics are getting mtu 1500.
Has anybody some documentation or hints on how to configure mtu 9000 for dynamic vnics (vm-fex) ?
Sent from Cisco Technical Support iPad App

Hi Alois,
The MTU size can be changed to the VM-FEX interface by using a QoS policy in the port-profile.
This is how you change the MTU size when using Vvm-fex:
1) Create a QoS policy under the LAN tab,
2) While selecting a Priority, pick the QoS system class which has a modified MTU size configured.
3) Create a port-profile to be used by a VMs NIC (which in turn will get it one of the dynamic interfaces)
4) In the port-profile specify this QoS Policy
Hope this helps!
./Abhinav

If MTU size will increase in cisco 3550 does it will impact any traffic ?

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