RESOLVED: dhcpd sporadically ignoring one of two "copies" of a DHCP request
p.mayers at imperial.ac.uk
Wed Mar 12 11:33:42 UTC 2014
On 12/03/14 11:21, Simon Hobson wrote:
> Phil Mayers <p.mayers at imperial.ac.uk> wrote:
>> This would solve a number of problems (e.g. giaddr is not routeable because it's a local-scoped RFC1918 block)
> You mean, it would workaround (not fix) a broken IP network ;-)
No, I don't mean that.
> By definition, if you have an address in use which is not routable, then your IP networking is broken - don't even get me started on NAT !
No. It is not routeable *from the DHCP server*. That doesn't mean it's
not routeable anywhere. It might be an RFC1918 range policy-routed into
a TTW registration server inside your POP, but not inside the backbone.
Or it might be routed down a GRE tunnel and you can't send the DHCP
packets that way because the (ahem) "interesting" networking code in ISC
dhcpd doesn't use a UDP socket like normal people, and can thus only
receive packets on interface types someone has bothered to code for.
(and the last time I tried USE_SOCKETS it was a mess of compile errors
Or you might be using an MPLS L3VPN, but punting DHCP packets into a
separate "services" VRF, and want the replies to go back to the PE
router IP inside the services VRF, not the giaddr in the customer VRF.
There are a bunch of reasons to want to send DHCP replies to addresses
which aren't giaddr, and none of them constitute "broken" IP network
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