06-28-2010 08:21 AM - edited 03-06-2019 11:47 AM
I had a question, why am I able to configure the MTU on a FastEthernet between 9216-9216? Is the MTU parameter under the copper interface meaning something else? Usually its between 1480 and 1524.
show run int fast 4/31
switchport
speed 100
duplex full
end
int fast 4/31
mtu ?
<9216-9216> MTU size in bytes
show int fast 4/31 status
Port Name Status Vlan Duplex Speed Type
Fa4/31 notconnect 1 full 100 10/100BaseTX
-Manny
Solved! Go to Solution.
07-02-2010 01:32 PM
Hi Manny
It appears that the mtu size command is in reference to egress traffic on a FastEthernet port.
See the config guide for 12.2(SXH)
Configuring a nondefault MTU size on a 10, 10/100, or 100 Mbps Ethernet port limits ingress packets to the global LAN port MTU size and permits egress traffic of any size larger than 64 bytes.
HTH
07-01-2010 08:55 AM
Manny,
according to http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml#c1
the MTU describes the largest physical packet size, measured in bytes, that a network can transmit. Any messages larger than the MTU are divided into smaller packets before transmission.
Smaller frames (while flowing through a network device) usually create more CPU interrupts and more processing overhead. In other words a higher MTU size (especially on GigE interfaces) means (generally spoken) a higher throughput.
The important thing is to have the higher MTU size configured through the whole network or fragmentation will take place.
--
Uwe
07-01-2010 03:18 PM
Manny
Certain line cards on the 6500 support jumbo frames. From the cli output, you have one of those line cards and that's why you are seeing 9216 as an option for MTU size.
HTH
07-02-2010 10:56 AM
Thanks for the link however, the linecard WS-X6548-RJ-45 allows MTU of only 9216 and not "1500-9216". Can you really push over 9K MTU over FastEthernet? If I'm misunderstanding the reasoning behind allowing jumbo MTU on FastE's please elaborate.
-Manny
07-02-2010 01:32 PM
Hi Manny
It appears that the mtu size command is in reference to egress traffic on a FastEthernet port.
See the config guide for 12.2(SXH)
Configuring a nondefault MTU size on a 10, 10/100, or 100 Mbps Ethernet port limits ingress packets to the global LAN port MTU size and permits egress traffic of any size larger than 64 bytes.
HTH
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: