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List:       freebsd-hackers
Subject:    Re: netgraph ability
From:       Ruslan Ermilov <ru () freebsd ! org>
Date:       2004-04-23 17:35:18
Message-ID: 20040423173518.GC2922 () ip ! net ! ua
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On Thu, Apr 22, 2004 at 05:50:57PM -0700, David Yeske wrote:
> I'm in a situation where I need to emulate multiple ethernet devices with
> different mac addresses.  I have gotten far enough to have this.
> 
> I ran ngctl and then ran
> "mkpeer . eiface hook ether"
> 
> I then ran
> ifconfig ngeth0 link '00:bd:03:11:21:11'
> ifconfig ngeth0 192.168.20.5
> ifconfig sis0 192.168.23.45
> 
> So basically I want to be able to ping / connect to 
> 192.168.20.5 from another box on the 192.168.23.0/24 network, and have it see
> the mac address that I have set rather than the mac address of my sis0 device.
> I know I can do this with vmware, but I am trying to avoid that.
> 
> Anyone know if this is possible?  Is there a way to do this with the tap device
> and or arpd?
> 
Using Netgraph, you can emulate any number of Ethernet interfaces
on one physical interface.  Here's my recipe for you:

1.  Load the ng_ether(4) module.
2.  Create the required number of ng_eiface(4) nodes.
3.  Connect "lower" and "upper" of sis0: and all ngethX:
    ng_ether(4) nodes to one ng_bridge(4).
4.  Make sure to "ngctl msg <if>: setautosrc 0" to all
    ng_ether(4) nodes.
5.  Optionally set net.link.ether.inet.log_arp_wrong_iface=0.

Here's my test (I've omitted obvious configuration steps):

# ifconfig dc0 ether
dc0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=48<VLAN_MTU,POLLING>
        ether 00:10:a4:c0:c0:45

# ifconfig ngeth0
ngeth0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        ether 00:00:00:01:02:03

# ngctl show bridge:
  Name: bridge          Type: bridge          ID: 0000000b   Num hooks: 4
  Local hook      Peer name       Peer type    Peer ID         Peer hook
  ----------      ---------       ---------    -------         ---------
  link4           ngeth0          ether        00000007        lower
  link3           ngeth0          ether        00000007        upper
  link2           dc0             ether        00000002        lower
  link1           dc0             ether        00000002        upper

# ifconfig ngeth0 1.2.3.4

# tcpdump -lenx -i dc0 ether host 0:0:0:1:2:3
tcpdump: listening on dc0
20:29:05.571179 0:0:0:1:2:3 ff:ff:ff:ff:ff:ff 0806 42: arp who-has 1.2.3.4 tell 1.2.3.4
                         0001 0800 0604 0001 0000 0001 0203 0102
                         0304 0000 0000 0000 0102 0304


Cheers,
-- 
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer

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