[Dnsmasq-discuss] Proxy DHCP KVM Virtualbox

Ryan A. Chapman ryan at rchapman.org
Mon Aug 18 07:04:39 BST 2014


Hi Gregg,

Does Alice have more than one network interface (one into 172.xx.xx and another into 192.168.x.x)?  If so, then try disabling reverse path checking in the kernel on alice with "cat /proc/sys/net/ipv5/conf/default/rp_filter; cat /proc/sys/net/ipv4/conf/all/rp_filter; echo 2 > /proc/sys/net/ipv4/conf/default/rp_filter; echo 2 > /proc/sys/net/ipv4/conf/all/rp_filter".  Note the old values in case you want to change them back (or just reboot alice).  If that doesn't work, then seeing the dhcp request/response would be helpful.  You can get that by doing a tcpdump on alice with "tcpdump -nnvvi any -s 0 port bootps or port bootpc".  Also please provide the ip addresses of the interfaces on alice and bob (at least the last octet).

Ryan


On Aug 17, 2014, at 9:41 PM, Gregg Stock <gregg at damagecontrolusa.com> wrote:

> Thank you in advance for taking a look at this.
> 
> I have an "interesting" problem trying to get a PXE boot system setup.
> 
> I have a dnsmasq server "Alice" that handles DNS and DHCP for several
> networks. I'm trying to add a PXE boot environment and am currently
> using two different PXE boot servers. Server "Bob" runs Cobbler for
> installations. Alice also runs TFTP/PXE and server some system recovery
> distros.
> 
> On the LAN network, I'm testing using Virtualbox. On our DMZ network,
> I'm using Libvirt/KVM.
> 
> Alice serves up boot menu using pxe-prompt that directs the user to the
> desired boot server. This works fine with Virtualbox but not with KVM.
> 
> From what I can gather using tcpdump, when I execute
> 
>          pxe-service=x86PC, "Cobbler LAN Installation Server",
> pxelinux, 172.xx.xx.35
> 
> tcpdump shows:
> IP 172.xx.xx.103.bootpc > 255.255.255.255.bootps:
> 
> And and everything goes smoothly
> 
> But when this executes...
> 
>     pxe-service=x86PC, "Cobbler DMZ Installation Server", pxelinux,
> 192.168.x.35
> 
> tcpdump shows:
> 192.168.x.35.bootpc > 255.255.255.255.pxe
> 
> The KVM guest issues bootpc and pxe but nobody is listening on 4011
> 
> Both requests are to the same server, just different interfaces.
> 
> I'm not sure how to proceed, it seems like I needs a DHCP proxy server
> to listen on port 4011 but it would be nice if I could keep the stuff
> that works on Virtualbox.
> 
> Best regards,
> 
> 
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