[c-nsp] IOS XR DHCP Proxy helper VRF != giaddr VRF

[Jason Lixfeld]

I’d like to relay DHCP broadcasts to a helper that lives in a different VRF than the one in which the giaddr lives, but I keep getting barked at:

RP/0/RSP0/CPU0:Feb  7 16:29:09.899 : dhcpd[1091]: DHCPD: TP2477: Inapplicable helper due to differing access & server interface VRFs with null GIADDR

Here’s where I’m going..

!
dhcp ipv4
 profile DHCP proxy
  helper-address vrf management 10.219.51.185 giaddr 0.0.0.0
  helper-address vrf management 10.219.51.249 giaddr 0.0.0.0
  relay information option allow-untrusted
 !
 interface Bundle-Ether1.127 proxy profile DHCP
 interface Bundle-Ether1.4001 proxy profile DHCP
!
interface Bundle-Ether1.127
 vrf residential-management
 ipv4 address 10.61.0.1 255.255.255.0
 encapsulation dot1q 127
!
interface Bundle-Ether1.4001
 vrf foo
 ipv4 address 10.69.69.1 255.255.255.248
 encapsulation dot1q 4001
!

For completeness, the debugs do suggest that the giaddr is getting set according to the VRF the profile is applied to:

RP/0/RSP0/CPU0:Feb  7 17:05:37.119 : dhcpd[1091]: DHCPD: TP1883: Giaddr not present, Set giaddr 10.61.0.1, chaddr 0001.47f8.7410
…
RP/0/RSP0/CPU0:Feb  7 17:15:25.771 : dhcpd[1091]: DHCPD: TP1883: Giaddr not present, Set giaddr 10.69.69.1, chaddr 0201.47f8.7412

I’m sort of doing this already in an older IOS environment, but the helper is not in a VRF (the giaddr is, though).  The reason I was forced to do it that way in IOS was because of a feature limitation on the old, non-sophisticated IOS platform I was using.  I imagine XR hotness should have no such limitation :)

NB:  I am *not* using the bng pie on this particular device.  I’m a little fuzzy on when and where I actually need bng.  I see references for dhcp ipv4 proxy in non-bng command reference guides (which is what I’ve been referring to for this configuration), so I’m making the assumption that bng isn't required, but maybe it is?

Oh, and this is in XR5.3.4:

RP/0/RSP0/CPU0:#show install active summary
Tue Feb  7 14:19:23.490 EST
Default Profile:
 SDRs:
   Owner
 Active Packages:
   disk0:asr9k-mini-px-5.3.4
   disk0:asr9k-mpls-px-5.3.4
   disk0:asr9k-mgbl-px-5.3.4
   disk0:asr9k-mcast-px-5.3.4
   disk0:asr9k-fpd-px-5.3.4
   disk0:asr9k-k9sec-px-5.3.4
   disk0:asr9k-px-5.3.4.CSCvb31992-1.0.0
   disk0:asr9k-px-5.3.4.CSCvb37291-1.0.0
   disk0:asr9k-px-5.3.4.CSCvb39379-1.0.0
   disk0:asr9k-px-5.3.4.CSCvb72705-1.0.0
   disk0:asr9k-px-5.3.4.CSCvb88426-1.0.0
   disk0:asr9k-px-5.3.4.CSCvb92687-1.0.0
   disk0:asr9k-px-5.3.4.CSCvb95320-1.0.0
   disk0:asr9k-px-5.3.4.CSCvc02589-1.0.0
   disk0:asr9k-px-5.3.4.CSCvc18067-1.0.0
   disk0:asr9k-px-5.3.4.CSCvc22207-1.0.0

RP/0/RSP0/CPU0:#

Thanks in advance!