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Duplex / Speed Questions

 
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djbraunva



Joined: 03 May 2009
Posts: 1

PostPosted: Sat Aug 22, 2009 2:18 am    Post subject: Duplex / Speed Questions Reply with quote

Hi there,
I've used (and appreaciated) all the tips in this forum and appreaciate everybody's time.

I have created a rather simple lab that leverages the internal dynamips switch with a 802.1q trunk to a physical 3500XL. Using a 802.1q trunk from the dynamips switch allows me to place virtual router interfaces into the same VLAN as physical ports on the 3500XL and allows virtual routers to communicate with real hosts and VMWare guests placed into different subnets. The lab is supposed to provide a a test bed for new ZFW security policies and will also be used to develop a VoIP configuration.

I am running into an issue where my virtual router interfaces linked to a VLAN on the dynamips virtual switch stop passing traffic periodically. Reloading the router and/or host seems to correct this issue, and my first guess is that there is a speed/duplex mismatch between the virtual router and physical switch. I was hoping that somebody has already run into this and has determined what the correct speed/duplex settings are for the virtual router interfaces connected to the virtual switch, and what speed/duplex settings I should have configured on the NICs in my linux host running dynamips. Also, I am wondering if I need to change the speed/ duplex setting on the physical swich port connected to VLAN trunk and would appreaciate hearing what has worked for others.

All router interfaces are connected to virtual switch ports (not bridged to the NIC), and the virtual switch has a single port that is bridged to a dedicatd NIC connected to the real switch (there is no IP address assigned to the NIC). FWIW, the dynamips host is running Ubuntu 9.04 (32bit) and has an Intel Pro/1000 NIC configured with a 9000B MTU.

I hope this is an easy for somebody out there! Thanks in advance.
DJB
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MrPaul



Joined: 17 Feb 2009
Posts: 139
Location: CCIE #19936

PostPosted: Sat Aug 22, 2009 10:25 pm    Post subject: Reply with quote

From what I can tell the virtual switch only does half duplex...at least that's what's negotiated.

In my setup I let the virtual routers auto-negotiate with the virtual switch. On my 'breakout' switch (the one that does the QinQ to connect to real switches) I set the ports to half duplex and disable cdp locally but enable cdp tunneling.

That ensures that I get my CDP messages but don't get all the chatter about duplex mismatch.

Also, half duplex would not cause your communication to stop. It just means that you can't send/receive at the same time.

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