Network tap0 interface?

[mikek147]

I've been upgrading my installation of the Debian distro using apt-get. I must say that this appears to be a rather easy way to keep current.

I have a question, though, that I think is not distro specific. After doing an apt-get dist-upgrade successfully, I noticed I couldn't get beyond my ISP's subnet router, out to the internet. I might add here that I have cable. So any user, including the router, on my subnet, I could 'ping'. However, if I tried to ping my ISP's DNS server, I'd get no response.

After looking around, doing netstat -rn and ifconfig -a, I noticed that I had a new interface called tap0. If I ifconfig tap0 down, I had normal Internet access again.

Can anyone tell me what package, firewall, proxy server, ipchains or whatever created this interface?

TIA -mk

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If it ain't broke, fix it till it is.

[warchild]

Guess 1: ethereal

From what I've read, tap0 is used sometimes when you need to sniff an ethernet interface. If you could find out what packages you installed when you ran that command, this might be able to narrow it down a bit. Does this update procedure leave a log or print stuff out to the screen?

[mikek147]

Thanks for the reply, warchild. In this case, tap0 was part of the ppp package install. This is the interface ppp would use for dialup. This set my system up such that it was treating my ISP's local subnet as a private subnet. As long as I tried to touch anything 24.30.80.0, of which I am a part of, things were OK. As soon as I tried anything outside of that net, it assumed I had to go through the tap0 interface. Since I don't use dialup, I removed the package and things are well.

Thanks again. -mk

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If it ain't broke, fix it till it is.

[Wavey Davey]

The ethertap device (tap0..) requires kernel support and is basically a virtual ethernet interface...
http://snafu.freedom.org/linux2.2/docs/ethertap.txt

It has a variety of uses, for example, by using a kernel with IP Masquerading and ethertap enabled, you can give your MacOS a local network IP address and configure Mac On Linux (MOL) to use the ethertap device as its network interface. Then through IP Masquerading Linux will act as a router between your MacOS running under MOL and the Internet.

[This message has been edited by Wavey Davey (edited 11-25-2000).]