11:11 a.m.
hi everybody
I'm looking at my setup and got stuck
I have a box with two NICs on the same subnet, and another
box similar, also two NICs on one subnet, all four NICs are
on the same subnet.
Now, that second box has also a virtual NIC (libvirtd's
bridge route mode) and VMs guests are using it, traffic to
that virtual net is routed via 1st real NIC. This second box
dhcrelays to the first box(dhcpd).
I see box-dhcrelay forwards to box-dhcpd, I see box-dhcpd
receives and offers a lease but that VM guest does not get it.
I have policy routing manually set in place so both boxes
can ping each other all NICs. (including virtual NIC on the
box-dhcrelay)
Moreover, that VM guest can ping both boxes' all NICs when
its IP address is set to manual.
It's RHEL7 and I'm only trying IPv4.
I'm hoping some can rule out (or suggest what might be
broken in) libvirt/policy based routing.
I see those offers box-dhcpd makes are exactly for the
subnet of box-dhcrelay's virtual NIC/subnet.
It's a pickle. An expert's thought would be great to hear.
1:58 p.m.
Okay. I may be missing something; from what you explicitly write about
subnets, it sounds like you only have one, but if you don't have two
subnets, why do you need a DHCP relay? SO. Assuming you have two
subnets:
* It sounds as if your DHCP request is generating an ACK.
* I'm 99% sure your ACK has to traverse the DHCP helper and wend its way
back to the originating host.
So I'd focus on the DHCP relay, to be sure that the ACK with lease info
is both arriving at it, and then being unicast to the MAC. tcpdump on
respective interfaces should do the trick (something like "tcpdump -i
<dhcp-server-facing interface> port 67" or somesuch to see if it
arrives, then swap it around to the other interface to see if it
leaves).
Good luck!
-Ken
P.S. I don't claim to be an expert, but I like to think I have a decent
handle on DHCP. If someone sees a flaw in my thinking, please do pipe
up -- I admit that this virtual stuff can be counterintuitive at times.
On 2015-11-10 12:11, lejeczek wrote:
hi everybody
I'm looking at my setup and got stuck
I have a box with two NICs on the same subnet, and another box
similar, also two NICs on one subnet, all four NICs are on the same
subnet.
Now, that second box has also a virtual NIC (libvirtd's bridge route
mode) and VMs guests are using it, traffic to that virtual net is
routed via 1st real NIC. This second box dhcrelays to the first
box(dhcpd).
I see box-dhcrelay forwards to box-dhcpd, I see box-dhcpd receives and
offers a lease but that VM guest does not get it.
I have policy routing manually set in place so both boxes can ping
each other all NICs. (including virtual NIC on the box-dhcrelay)
Moreover, that VM guest can ping both boxes' all NICs when its IP
address is set to manual.
It's RHEL7 and I'm only trying IPv4.
I'm hoping some can rule out (or suggest what might be broken in)
libvirt/policy based routing.
I see those offers box-dhcpd makes are exactly for the subnet of
box-dhcrelay's virtual NIC/subnet.
It's a pickle. An expert's thought would be great to hear.
_______________________________________________
libvirt-users mailing list
libvirt-users(a)redhat.com
https://www.redhat.com/mailman/listinfo/libvirt-users
4:30 a.m.
On 10/11/15 19:58, Ken D'Ambrosio wrote:
Okay. I may be missing something; from what you
explicitly write about subnets, it sounds like you only
have one, but if you don't have two subnets, why do you
need a DHCP relay? SO. Assuming you have two subnets:
yes, that - virtual NIC
(libvirtd's bridge route mode) - I
realize might have not been explicit, there is the second
subnet.
I' try to sniff that traffic.
thanks
* It sounds as if your DHCP request is generating an ACK.
* I'm 99% sure your ACK has to traverse the DHCP helper
and wend its way back to the originating host.
So I'd focus on the DHCP relay, to be sure that the ACK
with lease info is both arriving at it, and then being
unicast to the MAC. tcpdump on respective interfaces
should do the trick (something like "tcpdump -i
<dhcp-server-facing interface> port 67" or somesuch to see
if it arrives, then swap it around to the other interface
to see if it leaves).
Good luck!
-Ken
P.S. I don't claim to be an expert, but I like to think I
have a decent handle on DHCP. If someone sees a flaw in
my thinking, please do pipe up -- I admit that this
virtual stuff can be counterintuitive at times.
On 2015-11-10 12:11, lejeczek wrote:
> hi everybody
>
> I'm looking at my setup and got stuck
>
> I have a box with two NICs on the same subnet, and
> another box
> similar, also two NICs on one subnet, all four NICs are
> on the same
> subnet.
>
> Now, that second box has also a virtual NIC (libvirtd's
> bridge route
> mode) and VMs guests are using it, traffic to that
> virtual net is
> routed via 1st real NIC. This second box dhcrelays to the
> first
> box(dhcpd).
>
> I see box-dhcrelay forwards to box-dhcpd, I see box-dhcpd
> receives and
> offers a lease but that VM guest does not get it.
>
> I have policy routing manually set in place so both boxes
> can ping
> each other all NICs. (including virtual NIC on the
> box-dhcrelay)
> Moreover, that VM guest can ping both boxes' all NICs
> when its IP
> address is set to manual.
>
> It's RHEL7 and I'm only trying IPv4.
> I'm hoping some can rule out (or suggest what might be
> broken in)
> libvirt/policy based routing.
> I see those offers box-dhcpd makes are exactly for the
> subnet of
> box-dhcrelay's virtual NIC/subnet.
>
> It's a pickle. An expert's thought would be great to hear.
>
> _______________________________________________
> libvirt-users mailing list
> libvirt-users(a)redhat.com
> https://www.redhat.com/mailman/listinfo/libvirt-users
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lejeczek