Cannot get NIO_tap interface to work (consistently)
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Author:  willdawg [ Sun Jan 08, 2012 7:55 pm ]
Post subject:  Cannot get NIO_tap interface to work (consistently)

Hi all,

I'm running GNS3 0.7.2, with Dynagen 0.12.100613 and Dynamips 0.2.8-RC2.

I have a GNS3 lab where a device (QEMU ASA5520) is connected to my host PC via "NIO_tap:tap0" (indirectly thru a GNS3 switch.) I instantiated the tap0 interface as root via the commands:
modprobe tun
tunctl -u <myusername>
ifconfig tap0 netmask up

This creates the tap0 int with ownership by my user, which is the user I'm launching GNS3 with (anotherwords, i don't have to launch GNS3 with root perm's.)

So I can start GNS3 as my user and bring up my lab, and the connection from the ASA (at IP addr works at least for a while; but ofttimes, the "virtual cable" between the ASA and my host gets "disconnected", as I cannot successfully arp any longer for the connected host on either side.

I've also created a Dynagen lab with a router connection to NIO_tap:tap0, and I can launch this under my user account, but I cannot successfully do ARP (or IPv6 neighbor solicitation) between the router and my host.

What I'd like to know is how I could test connecting to the tap0 interface with something other than GNS3/Dynagen, so I could tell if it's a tap0 problem (not likely, but...) or if it's a GNS3/Dynagen problem connecting to the tap0 int. Any suggestions?


Author:  willdawg [ Mon Jan 09, 2012 4:04 am ]
Post subject:  Re: Cannot get NIO_tap interface to work (consistently)

Here's what I see (and should always see) when the NIO_tap:tap0 is working correctly (tshark cap from the tap0 int):
29867.604526 3e:6b:a4:4f:27:c8 -> 00:aa:00:a9:f6:00 ARP Who has  Tell
29867.605028 00:aa:00:a9:f6:00 -> 3e:6b:a4:4f:27:c8 ARP is at 00:aa:00:a9:f6:00

When things break, I don't see the "is at" response...

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