Hi Dave,
Don't have experience with your specific case, just a common sense
speculation. When you configure local dhcp server it usually specifies a
template interface, like demux0.0, pp0.0, psX.0. Probably in your case a
conflict happens when junos tries to enable both server and relay on the
same subscriber interface. Maybe if you could dynamically enable dhcp
server or relay for a particular subscriber interface it could solve the
issue. Regarding interface separation, I'm not sure if it's possible to
have more than one demux or pp interface, I believe only demux0 is
supported. With ps interfaces you however can have many of them and if
you can aggregate subscribers to pseudowires by service, you could
enable dhcp server or relay depending on psX interface. However,
pseudowires might be not needed and excessive for your design.
Did you try to analyze DHCP and AAA traceoptions and capture DHCP
packets, BTW?
Kind regards,
Andrey
Dave Bell via juniper-nsp писал(а) 2023-01-05 08:50:
Hi,
I'm having issues with DHCP relay on a Juniper MX BNG, and was
wondering if
anyone had an insight on what may be the cause of my issue.
I've got subscribers terminating on the MX, authenticated by RADIUS,
and
then placed into a VRF to get services. In the vast majority of cases
the
IP addressing information is passed back by RADIUS, and so I'm using
the
local DHCP server on the MX to deal with that side of things.
In one instance I require the use of an external DHCP server. I've got
the
RADIUS server providing an Access-Accept for this subscriber, and also
returning the correct VRF in which to terminate the subscriber. I've
also
tried passing back the external DHCP server via RADIUS.
In the VRF, I've got the DHCP relay configured, and there is
reachability
to the appropriate server
The MX however seems reluctant to actually forward DHCP requests to
this
server. From the logging, I can see that the appropriate attributes are
received and correctly decoded. The session gets relocated into the
correct
routing instance, but then it tries to look for a local DHCP server.
I have the feeling that my issues are due to trying to use both the
local
DHCP server and DHCP relay depending on the subscriber scenario. If I
change the global configuration of DHCP from local server to DHCP
relay, my
configuration works as expected though with the detriment of the
scenario
where the attributes returned via RADIUS no longer work due to it not
being
able to find a DHCP relay.
Since the MX decides how to authenticate the subscriber based on where
the
demux interface is configured, I think ideally I would need to create a
different demux interface for these type of subscribers that I can then
set
to be DHCP forwarded, thought I don't seem to be able to convince the
router to do that yet.
Has anyone come across this, and found a workable solution?
Regards,
Dave
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