Virtualized Network Problems

March 28, 2008 1:31 PM

I'm having network problems with virtualized systems. I have Macs runnig OsX 10.4 with Parallels running XP. At random times, the network fails...kinda

The network will stop working (cant get to Internet, internal hosts, email, pings, DHCP) but the network link never goes down. Link lights are on, switch says port is active and in proper vlan. Snoops on the interface and switch port the show computers trying to get a DHCP address. If someone has music streaming from the Internet, it will continue to function. Any new sessions will fail. I can fix it by pulling the network cable and plugging it back in. This only happens on systems with Parallels w/ XP but it can happen even when Parallels/XP is NOT running.

What can be causing this? What can I look at?

posted by nivekraz to computers & internet (9 comments total)

Bridged or shared mode of networking? I only have a few seconds here, but try switching modes and see if that helps. I have had better luck with shared in the past.
posted by Silvertree at 1:40 PM on March 28, 2008

Opps..They are bridged and have to be that way for authentication and domain managemnt reasons. So 2 different mac addresses are send out. However, the network dies even when the guest os is not running.
posted by nivekraz at 1:56 PM on March 28, 2008

Your computer is almost certainly sending out packets with source IP addresses that aren't on your network and are just confusing the nearest router. Your network may be reacting to this.
posted by oaf at 2:34 PM on March 28, 2008

Oh, wait, it may be something else. I've only seen this with 10.5.
posted by oaf at 2:35 PM on March 28, 2008

nivekraz, I'm confused by your second comment about the networking dying with the guest os not running. If it happens when you're not running the guest os, then what makes you think it's caused by the guest os?
posted by tcv at 5:57 PM on March 28, 2008

So 2 different mac addresses are send out

I wouldn't be at all surprised to find that this is the root of the problem.
posted by flabdablet at 8:12 PM on March 28, 2008

Are you using proxies? Try disabling them. I've seen this happen when I've fat fingered the proxy settings (on the Mac side)
posted by Gungho at 8:24 PM on March 28, 2008

Some clarification:
-This problem only happens on machines with parallels installed.
-When both OSs are running, the eth0 is bridged mode. Each OS will have it's own MAC address. So t the rest of the network it looks like two independent computers.
-This setup works most of the time.
-The network will die when both OS are running and when the only the host OS is running. This doesnt happen on machines without Parallels and only one OS.
-No proxies are being used.
-Activity can be seen on the link with Wireshark but new sessions can start.

It's weird. Thanks for any input
posted by nivekraz at 12:51 PM on March 29, 2008

The fact that your network has to be configured a certain way "for authentication and domain management reasons" suggests to me that you're probably connecting to professional-grade managed network switches. Are you sure that the switches your Parallels-enabled computers are attached to are not doing the kind of enforce-one-MAC-per-port silliness beloved of cable companies and the more annoying university network sysadmins?
posted by flabdablet at 9:17 PM on March 29, 2008