Traffic limiting issue.

Unanswered Question
Aug 9th, 2009

I have the following config on a Cisco router that is being used as a test lab for our server team. We are simulating some of our WAN connections.

interface GigabitEthernet0/12

switchport access vlan 50

switchport mode access

speed 10

duplex full

srr-queue bandwidth limit 10

spanning-tree portfast

interface GigabitEthernet0/13

switchport access vlan 120

switchport mode access

speed 10

duplex full

srr-queue bandwidth limit 20

spanning-tree portfast

So port 13 is limited to 10% of the bandwidth and port 12 is limited to 30%

The issue I'm having is that if these two 'WAN Connections' were to transfer files between each other you would think that the speed would be of the slowest link, but that is not the case. If a computer on port 13 downloads from 12 it gets up to about 340KB, which is way more that port 12 should be able to handle

If computer on port 12 downloads from 13 then the max speed it gets is about 64KB, which is what i expect.

So is there a way to get this to act in a asymmetrical way and not a symmetrical way which it seems to be doing at the moment? i.e. if port 13 downloads from port 12 then speeds shouldn't go above 10% of the link....

thanks.

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Joseph W. Doherty Mon, 08/10/2009 - 03:00

"interface GigabitEthernet0/12

switchport access vlan 50

switchport mode access

speed 10

duplex full

srr-queue bandwidth limit 10

spanning-tree portfast

interface GigabitEthernet0/13

switchport access vlan 120

switchport mode access

speed 10

duplex full

srr-queue bandwidth limit 20

spanning-tree portfast

So port 13 is limited to 10% of the bandwidth and port 12 is limited to 30%"

Actually, you've defined port 13 limited to 20% (egress) and port 12 limited to 10% (egress). Also these values are not always exact.

"Usage Guidelines

If you configure this command to 80 percent, the port is idle 20 percent of the time. The line rate drops to 80 percent of the connected speed. These values are not exact because the hardware adjusts the line rate in increments of six. "

From: http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_50_se/command/reference/cli3.html#wp1947391

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