Hi, depending on the IOS and type of unit you have you could very well support flow control on your trunk links. Issue the "show interface capabilities" command and the switch will list the abilities of each port for you. HTH

sib-124-sw1#show interface capabilities


Model: WS-C3550-24-PWR

Type: 10/100BaseTX

Speed: 10,100,auto

Duplex: half,full,auto

Trunk encap. type: 802.1Q,ISL

Trunk mode: on,off,desirable,nonegotiate

Channel: yes

Broadcast suppression: percentage(0-100)

Flowcontrol: rx-(off,on,desired),tx-(none)

Fast Start: yes

QOS scheduling: rx-(1q0t),tx-(4q0t),tx-(1p3q0t)

CoS rewrite: yes

ToS rewrite: yes

UDLD: yes

Inline power: yes

SPAN: source/destination

PortSecure: yes

Dot1x: yes


Model: WS-C3550-24-PWR

Type: 10/100BaseTX

Speed: 10,100,auto


erikhoehne Mon, 01/28/2008 - 18:46
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I'm running CatOS. The port shows to have the capabilities. However, I was concerned it might give me an error when trying to enable flow control since the port is a dot1q trunk. I can't find any info on Cisco's website saying it isn't possible, so I'm thinking it will work.

I'll give it a try during our next maintenance window.

Thanks for the reply!



Hi Erik, on the cat-os your command maybe show port abilities, you can do the show port ? to confrim the correct syntext. Trunk link have to have the exact configurations on both sides to work properly. If you get an error check the other sides config for any mismatches HTH

erikhoehne Tue, 01/29/2008 - 12:46
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Good Afternoon William,

The main reason I was thinking the switch might give me an error; even though the switch port shows to have flow control capabilities, is trunk links act a bit different. In the past, the switch has spit out an error at me when trying to enable certain protocols on the trunk links; even though the switch port shows it's capable.

Thanks for the tips buddy;-)




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