12-09-2013 01:49 PM - edited 03-07-2019 05:00 PM
Hello,
I'd like to know if applying the below commands to configure the L2 MTU size to a size larger than the defual size(1500) would have any disruptive effects on the production switch.
Thanks in advance.
Best, ~sK
o configure the system jumbo maximum transmission unit (MTU) size for Layer 2 interfaces, use the system jumbomtu command.
system jumbomtu size
size | Even number between 1500 and 9216. |
Defaults
The system jumbo MTU default size is 9216 bytes and the interface default MTU is 1500 bytes.
Global configuration mode
Supported User Roles
network-admin
vdc-admin
Release | Modification |
---|---|
4.0 | This command was introduced. |
Use the system jumbomtu command to specify the MTU size for Layer 2 interfaces. The range is from 1500 to 9216.
The physical level uses an unchangeable bandwidth of 1 GB.
This command does not require a license.
This example shows how to configure the system jumbo MTU as 8000 bytes and how to change the MTU specification for an interface that was configured with the previous jumbo MTU size:
switch# config t
switch(config)# system jumbomtu 8000
switch(config)# show running-config
switch(config)# interface ethernet 2/2
switch(config-if)# switchport
switch(config-if)# mtu 4608
Solved! Go to Solution.
12-09-2013 05:59 PM
Hello,
Glad to know there were no problems bud.
Now the explanation.
When changing the mtu to a lower value you got to be careful as there might be hosts that will send traffic over the setting configured in ur interface.
If this happens 2 things could happen and both of them depending on whether the host send the traffic with the df bit set on the IP header.
Fragment the packet if df not set
Send a fragmentation needed icmp packet if df is set.
If you change the value to a higher level no problem will be shown.
Remember that a mismatch within mtu interface values on OSPF will never allow u to build a ospf adjacency.
If u do not have any other question please mark it as resolved
Sent from Cisco Technical Support Android App
12-09-2013 03:58 PM
Applied the commands. No interruptions occured.
Thanks!
12-09-2013 05:59 PM
Hello,
Glad to know there were no problems bud.
Now the explanation.
When changing the mtu to a lower value you got to be careful as there might be hosts that will send traffic over the setting configured in ur interface.
If this happens 2 things could happen and both of them depending on whether the host send the traffic with the df bit set on the IP header.
Fragment the packet if df not set
Send a fragmentation needed icmp packet if df is set.
If you change the value to a higher level no problem will be shown.
Remember that a mismatch within mtu interface values on OSPF will never allow u to build a ospf adjacency.
If u do not have any other question please mark it as resolved
Sent from Cisco Technical Support Android App
12-10-2013 01:47 PM
Thanks, Julio!
I appreciate that respose.
Best, ~sK
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