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Re: [Xen-users] Basic Network Bridge

  • To: xen-users@xxxxxxxxxxxxx
  • From: Alexandre Kouznetsov <alk@xxxxxxxxxx>
  • Date: Fri, 22 Jun 2012 17:05:21 -0500
  • Delivery-date: Fri, 22 Jun 2012 22:06:45 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

El 22/06/12 14:54, Eric Lindsey escribió:
This from dom0 (www):
15:39:30.506858 IP> BOOTP/DHCP,
Request from 00:16:3e:5a:65:3c, length 300
15:39:30.506993 IP> BOOTP/DHCP, Reply, length 305
Your exchange is abnormal. Take a look on this good one:

15:46:25.031591 IP > BOOTP/DHCP, Request from 00:26:6c:10:5a:4d, length 300 15:46:26.002892 IP > BOOTP/DHCP, Reply, length 300 15:46:26.004265 IP > BOOTP/DHCP, Request from 00:26:6c:10:5a:4d, length 316 15:46:26.033630 IP > BOOTP/DHCP, Reply, length 305

There are four messages involved:
Client: I need IP! (DHCPDISCOVER)
Server: have X available for you (DHCPOFFER)
Client: I request X! (DHCPREQUEST)
Server: your use of X is acknowledged (DHCPACK)

After that, the client only renews the lease, so the server is aware of this lease steel being needed. They only exchange DHCPREQUEST and DHCPREQUEST, unless a DHCPREQUEST is denied for some reason.

So, in your case, there are two details:
1. Only two messages are visible, not four.
2. DHCP server sends replay to, not

I think your dnsmasq is treating your client as if it had a valid leases, while your client feels completly new. Probably, cleaning the leases cache would solve the issue (/var/lib/misc/dnsmasq.leases).

Check your Dnsmasq configuration to make sure this does not happen again.

Haha I can't install tcpdump on domU because it has no Internet access.
Assigned static information on domU in /etc/network/interfaces, and
everything is golden.  DNS works, Internet works, network works!
That isolates the issue to DHCP service, converting this thread in a offtopic (:

Is my dom0 trying to send the DHCPOFFER directly to a specific IP
address ( from the look of things) when the eth0 interface
on domU doesn't have an address yet (hence the DHCP request)?
That's the point.

Alexandre Kouznetsov

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