MTU on subinterfaces

[Antonio_1_2]

Hello,

is there a way to change MTU on subinterfaces? i.e on one physical interface one subinterface has MTU 1900 and other has 1500?

I need that for xconnect (connection doesn't get up becuase MTU on endpoints are not equal).

(On one side of xconnect I have 9216 bytes MTU and on the other 1500 bytes MTU, and I can't lower these 9216 Bytes on main interface cause I already have some existing xconnect links that require 9216Bytes)

regards,

A.

[Shelley Bhalla]

No. MTU is taken form the main interface hence cannot change.

Doesn't the 1500 MTU side interface support jumbo frames?

Shelley.

[Antonio_1_2]

Hello,

It is Cisco 2811 and it only supports up to 1600 bytes as I can see.

C2811(config)#interface fastEthernet 0/1
C2811config-if)#mtu ?
  <64-1600>  MTU size in bytes

regards,

A.

[Shelley Bhalla]

You could probably buy a gigabit wan card for the 2800 that supports Jumbo frames for the 2811 and you are golden!

http://www.cisco.com/en/US/prod/collateral/routers/ps5854/prod_qas0900aecd80169bf0_ps5949_Products_Q_and_A_Item.html

Q. What is the HWIC-1GE-SFP?
A. The HWIC-1GE-SFP is a single-wide HWIC with one Small Form-Factor Pluggable (SFP) slot. The SFP slot can be populated with Cisco copper and optical Gigabit Ethernet SFPs to provide 1-port Gigabit Ethernet connectivity on all Cisco Integrated Services Routers. The HWIC does not come with any default SFP; it must be ordered separately. For a list of SFPs supported, please refer to Table 1.

Q. What is the maximum throughput on the Gigabit Ethernet HWIC?
A. The HWIC bus interface is limited to 400 Mbps of full duplex. The actual throughput of the Gigabit Ethernet HWIC is limited by the throughput of individual platforms. Under bidirectional traffic of 1518 bytes or larger, the Gigabit Ethernet HWIC can support up to an aggregate of 350 Mbps on Cisco 2811 and 2821 routers, 400 Mbps on Cisco 2851 routers, and 500 Mbps on Cisco 3800 Series platforms.

Q. Are jumbo frames supported?
A. Yes. The maximum transmission unit (MTU) is user-configurable and can be set from 64 to 9576 bytes. The MTU specifies the size of the Ethernet packet payload, excluding the Ethernet header.

[Antonio_1_2]

Hello,

thanks for the information. Just one question regarding hwic card you proposed:

it says :Under. bidirectional traffic of 1518 bytes or larger, the Gigabit Ethernet HWIC can support up to an aggregate of 350 Mbps on Cisco 2811 

Is this mean that if I configure router 2811 on the stick with only this port (HWIC-1GE-SFP), traffic rate can go up to 350Mbps?

regards,

A

[Shelley Bhalla]

It means that even though the card itself can support 1gbps bt on this platform it will give only 350 megs. This could be a platform limitation instead of the card limitation.

You will certianly need to do more research on this before you buy. At the end of the day you need some card that supports jumbop frames on the far end to resolve this issue.

Shelley.

[Antonio_1_2]

Hi,

I ask this because in Cisco documentation router performance for Cisco 2811 with CEF enabled is maximum 61,44Mb/s, So with this card I can have 350Mb/s with C2811 platform?

Thank you,

A