Change MTU on Cat4006

Hi,
I have a Catalyst 4006 with a Sup2 engine, and a 6 port GigE card.
I need to change the default system MTU from 1500 to 1546 to resolve some MPLS over Ethernet issues i am having.
How do i do this?
On an IOS switch, i would use system mtu 1546, but how is this done in CatOS.
Thanks in advance
Darren

Catalyst 4000 Series
You can classify the Catalyst 4000 series switches into two groups in relation to jumbo or baby giant support:
Supervisor I (WS-X4012) and Supervisor 2 (WS-X4013)
Supervisor III (WS-X4014) and Supervisor IV (WS-X4515)
Supervisor I (WS-X4012) and Supervisor 2 (WS-X4013)
This group includes the WS-C2948G, WS-C2980G, and the WS-C4912G fixed-configuration switches also. Due to an ASIC limitation, there is no support for baby giants or jumbo.
Workaround
As a workaround, you can enable a port for trunking in order to support baby giants. When you enable a port for 802.1q trunking, the switch automatically assumes that an extra four bytes of data are appended on, and increment the frame size of the L2 packet. Note that ISL encapsulation is not supported on these platforms.
Hence, for implementations that require exactly one tag to be carried (either 802.1q or MPLS, but not both), you can configure the port as a trunk port to force the switchport to accept an extra four bytes of data. If the port were to carry multiple VLANs for VLAN-ID tagging or 802.1p prioritization, configure the port as a 802.1q trunk. However, even if VLAN tagging is not necessary, but you want the increased four-byte support, you can configure the port as a 802.1q trunk. Change the Native VLAN to be the one desired to carry the traffic. When you do so, you can accommodate an extra four bytes of data.
No jumbo frame support on any Cat4000 based switch (which includes the 400x, switches) due to the limitation of the Cat4000 asic.
regarding the workaround above Up to a max 1522 bytes is supported on ports enabled for .1q. Anything above that will fail.
Please rate helpful posts.

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asdftroy wrote:
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Attach the screen shots following.
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Hi,
I am having problem here. Previously, when the MTU was 1508...The cpu load was <5%. When changed to 1512, the load was increasing 70%. Recently, changed to 1522, the load is >95%. Not sure what's going with the configuration. But I can a lot ques dropping. Should I put on the port-channel 1? For more details configuration, please refer to attached file
hold-queue 1024 in
hold-queue 1024 out
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CPU utilization for five seconds: 96%/38%; one minute: 96%; five minutes: 96%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
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165 150300 11396947 13 0.07% 0.01% 0.00% 0 Tag Control
193 2608887200 237733062 10974 52.23% 52.71% 52.44% 0 Tag Input
304 4692 36566 128 0.00% 0.00% 0.00% 0 Tagcon Addr
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Here are the instructions to setup inband span (which monitors traffic sent
to the MSFC):
Router#monitor session 1 source interface fa 3/3 !--- Use any interface that
is administratively shut down.
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Now, go to the SP console. Here is an example:
Router#remote login switch
Router-sp#test monitor add 1 rp-inband rx <--- check the syntax as it varies
from one IOS to the next so use ?
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Ingress Source Ports: 3/3 15/1
Egress Source Ports: 3/3
Ingress Source Vlans:
Egress Source Vlans:
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Go back to the RP and verify the monitor session as well:
Router#show monitor
Session 1
Type : Local Session
Source Ports :
Both : Fa3/3
Destination Ports : Fa3/2
SP console:
Router-sp#test monitor session 1 show
Ingress Source Ports: 3/3 15/1
Egress Source Ports: 3/3
Ingress Source Vlans:
Egress Source Vlans:
Filter Vlans:
Destination Ports: 3/2
To remove the inband span from sp do test monitor session 1 del and from the rp do no mon sess all
===============================
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Its now a few months since i last played with networking in zones, but i don't think you can do that. IIRC there are only a limited set of options which can be set to a shared interface which belongs to a zone.
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How to change MTU?

hey all. how i can change the MTU permanantly?

lucke wrote:
Echo the desired value to /sys/class/net/eth0/mtu (add "echo value > /sys/class/net/eth0/mtu" to /etc/rc.local to make it permanent).
Creating an iptables rule should also work, but that's a bit more complicated solution.
ok, that didnt work. it didnt kill my net this time, but ifconfig says MTU is still at 1500. there is also an error line at bootup. it goes by so fast (arch boots soo FAST i luv it!) that i cant read it all. but i did catch that its refering to the echo line in /etc/rc.local.
heres how i have it entered in rc.local
!/bin/bash
# /etc/rc.local: Local multi-user startup script.
#set mtu
"echo 1492 > /sys/class/net/eth0/mtu"
does that look right?

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Maybe this is a dumb question but here goes... I understand why somebody would want to change the MTU on a router but when you say you cannot get internet because it cannot be changed I lose you.
Could you provide more detail?

Changing MTU

How do you change the MTU on a router?
Message Edited by Doc Holliday on 09-16-2007 11:39 AM

no user name...leave it blank
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I made a Link Aggregation on a T2000 with e1000g1 & e1000g2 successfully.
Now i want to raise up the mtu size to mtu 9000 for the aggregation.
I tried /etc/hostname.aggr
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also not successfully
MaxFrameSize=0,2,2,2;
# 0 is for normal ethernet frames.
# 1 is for upto 4k size frames.
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Bug is described:
http://sunsolve.sun.com/search/document.do?assetkey=1-1-6326664-1
Solution is
T-Patch 125020-01
Message was edited by:
sunibk

MTU And change connection's MTU limit

Changed MTU to 1472.
Not open VPN with SonicWALL
netextender on my PC windows 7
pro 64 bit
Should changed MTU on a
windows 7 pro 64 bit.
I found a Fixit from Microsoft,
64 bit, but the error message:
were not for this computer.
http://support2.microsoft.com/kb/826159
This was over for PPP
connections.
shall have a fixit for non
PPP connections.
Has the internet with cable
connection. DHCP
Where can I find such a
fixit to change the MTU setting
on nettverksortet to
1472.
or a program that can change this.
Gunnar
gunnar jensen

Hi gunnar jensen,
We can change the MTU from the command line.
Open the command Prompt window and follow the steps below to change the MTU size:
Type “netsh interface ipv4 show subinterface”.
Press Enter.
You will see a list of network interfaces.
Type “netsh interface ipv4 set subinterface `Local Area Connection` mtu=1472 store=persistent”.
You should replace Local Area Connection with the name that appeared in the “Interface” column from steps 1-3.
Press Enter.
Type “netsh interface ipv4 show subinterface” to check the result.
Best regards

Infiniband Mellanox MTU size change

Hello to all.
I am new to Solaris and know nothing about its administration tools.
We are willing to test Infiniband and need to change MTU of the adapter (Mellanox) to 4K (which is the default configu for our subnet manager).
Which command should be used to archieve the task ?
Next we need to configure an SRP target. Any specific howto ?
Thanks in advance for your kind reply

Thank you for your reply, Darren.
As per my test, ifconfig will work for the IPoIB (when creating a derivative interface to run IP over infiniband).
Actually the driver is installed, link comes up, fabric negotiates 2048 MTU and no interface is available to configure for IPoIB since I did not create it.
Ifconfig lists only the gigabit eth nic, since no ib0 card is defined (only ib device in /proc).
I am not going to run IP over Infiniband, al least not for storage access, since poses a huge penalty in performance.
To configure the device MTU (not the virtual ethernet over infiniband MTU) I think must be done at driver level, using something related to the low level adapter
cfgadm_ib(1M) - InfiniBand hardware-specific commands for cfgadm
datadm(1M) - maintain DAT static registry file
ifconfig(1M) - configure network interface parameters
libdat(3LIB) - direct access transport library
ib(4) - InfiniBand device driver configuration files
ibmf(7) - InfiniBand Management Transport Framework
daplt(7D) - Tavor uDAPL service driver
ib(7D) - InfiniBand Bus Nexus Driver
ibcm(7D) - InfiniBand Communication Manager
ibd(7D) - Infiniband IPoIB device driver
ibdm(7D) - Solaris InfiniBand device manager
tavor(7D) - InfiniBand (IB) Tavor driver
I guess it wil be cfgadm, but do not know syntax and parameters.
In vmware, using Mellanox tools, you issue esxcfg-module -s "port_type_default=1 set_4k_mtu=1" mlx4_en, where mlx4_en is the kernel module.
How to achieve this with Solaris ?
As per the SRP question, if Solaris supports COMSTAR it should support SRP target mode, right ?
Thank for sharing your thoughts.

Change MTU on Cat4006

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