server with two NICs and relayed to

[lejeczek]

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) and VMs guests are using it, traffic is routed via
1st NIC to that virtual net. 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 pings each other all NICs. (including virtual NIC on the
box-dhcrelay)
Moreover that VM guest can ping both boxes' all NICs when
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) DHCP config.
I see those offers box-dhcpd makes are exactly for the
subnet of box-dhcrelay's virtual subnet.

It's a pickle. An expert's thought would be great to hear.
_______________________________________________
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

[Simon Hobson]

lejeczek <[hidden email]> wrote:

> hi everybody
> Now, that second box has also a virtual NIC (libvirtd's bridge) and VMs guests are using it, traffic is routed via 1st NIC to that virtual net. 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.

Follow the packets. Use your preferred packet sniffing tool to see where the packet gets lost. Does it leave the DHCP server ? Does it reach the other server ? Is there a firewall that might block it ? Does the relay log that it's received it ? Does it leave the (virtual) nic from the relay ? Does it reach the (virtual) nic on the client ?

All you know at the moment is "it doesn't work". Follow the trail, and then you'll know that it fails at a specific location and you can then try and work out why.

BTW - I don't like the sound of "policy routing", for almost every non-broken network it is not required.

_______________________________________________
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

[lejeczek]

On 10/11/15 17:29, Simon Hobson wrote:
> BTW - I don't like the sound of "policy routing", for almost every non-broken network it is not required.
but after looking it up I understand that if one wants to -
have a box two(or more) NICs on same one subnet and be able
to pass traffic from another subnet to such a box then one
must use/setup policy based routes, no?
what would you recommend to sniff the packets?

many thanks.
_______________________________________________
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

[Niall O'Reilly]

On Tue, 10 Nov 2015 17:55:30 +0000,
lejeczek wrote:
>
> what would you recommend to sniff the packets?

  tcpdump

_______________________________________________
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users