Re: tap devices and DHCP.

From: Marcin Jessa (lists_at_yazzy.org)
Date: 09/22/05

  • Next message: Justas Jakubauskas: "Re: "ifconfig -vlandev" syntax" 
    Date: Thu, 22 Sep 2005 12:50:03 +0200
To: Robert Watson <rwatson@FreeBSD.org>

    On Thu, 22 Sep 2005 11:35:06 +0100 (BST)
    Robert Watson <rwatson@FreeBSD.org> wrote:

    >
    > On Thu, 22 Sep 2005, Marcin Jessa wrote:
    >
    > > I do not know if it's meant to be that way but tap devices cannot
    > > get IPs assigned with DHCP. I did not check the old dhclient code
    > > but the new one cannot hand over DHCP requests to tap devices. I
    > > was sure a tap device acted as an ethernet device even though it's
    > > a virtual one, since one can manually assign IP to tap. It can
    > > however assign IP to a bridge (with DHCP) with dev tap as a member
    > > of it. Could someone explain me please if this behaviour is on
    > > purpose or just a problem with DHCP?
    >
    > That's certainly undesirable. Could you tell us a little bit about
    > the setup you're running? Specifically, what's on the other end of
    > the tap device, and how does it hook up to the DHCP server?

    I have a bridge with one fxp0 nic (which I renamed to net0) and one tap1
    device. The other end runs linux as DHCP server on LAN.
    It communicates with the DHCP server through the fxp0 device which is a
    member of the same bridge.

    > Could you show the ifconfig output for the interface before and after
    > running dhclient? And then again after manually assigning an address?

    # ifconfig bridge0 create
    # ifconfig bridge0 addm net0 stp net0 addm tap1 stp tap1 up

    wlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
            inet6 fe80::212:f0ff:fe12:29b3%wlan0 prefixlen 64 scopeid 0x1
            inet 0.0.0.0 netmask 0xff000000 broadcast 255.255.255.255
            ether 00:12:f0:12:29:b3
            media: IEEE 802.11 Wireless Ethernet autoselect mode 11g
    (DS/2Mbps) status: associated
            ssid XXYYZZ channel 2 bssid 00:20:a6:4c:ef:62
            authmode OPEN privacy OFF txpowmax 100 protmode CTS bintval 100
    net0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu
    1500 options=8<VLAN_MTU>
            inet6 fe80::20a:e4ff:fe2f:9dce%net0 prefixlen 64 scopeid 0x2
            ether 00:0a:e4:2f:9d:ce
            media: Ethernet autoselect (100baseTX <full-duplex>)
            status: active
    pflog0: flags=0<> mtu 33208
    pfsync0: flags=0<> mtu 2020
    lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
            inet6 ::1 prefixlen 128
            inet6 fe80::1%lo0 prefixlen 64 scopeid 0x5
            inet 127.0.0.1 netmask 0xff000000
    tap0: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
            ether 00:bd:16:8d:03:00
    tap1: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu
    1500 inet6 fe80::2bd:16ff:fe8d:301%tap1 prefixlen 64 scopeid 0x7
            inet 0.0.0.0 netmask 0xff000000 broadcast 255.255.255.255
            ether 00:bd:16:8d:03:01
    bridge0: flags=8041<UP,RUNNING,MULTICAST> mtu 1500
            inet 192.168.2.222 netmask 0xffffff00
            ether ac:de:48:ca:32:d3
            priority 32768 hellotime 2 fwddelay 15 maxage 20
            member: tap1 flags=7<LEARNING,DISCOVER,STP>
            member: net0 flags=7<LEARNING,DISCOVER,STP>

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