PXE boot on SDA not working

[HAT]

Hi All

I m working on setting  up PXE  boot for SCCM device builds over the network . We are using an SDA network where I have configured IP helper on the SVI the endpoints are connected to . This is the configuration on the Fabric Edge node 

SDA-EDGE-POC-1#sh run interface vlan 1025
Building configuration...

Current configuration : 397 bytes
!
interface Vlan1025
description Configured from Cisco DNA-Center
mac-address 0000.xxx.f65d
vrf forwarding Corporate_VN_POC
ip address 10.223.7.1 255.255.255.0               
ip helper-address 172.28.251.10    <------------ DHCP Server ( Cisco 3650 switch ) 
ip helper-address 172.28.86.174    <------------ SCCM Server 
ip helper-address 172.28.86.175    <------------ SCCM Server 
no ip redirects
ip route-cache same-interface
no lisp mobility liveness test
lisp mobility 10_223_7_0-Corporate_VN_POC-IPV4
end

I m unable to get it working - stuck on the "start pxe over ipv4" screen . As per the attached pcap it look like it doesn't even go past the DHCP Discovery process . However I can also successfully obtain an IP address from the expected DHCP pool while connecting a random device to the same interface . I can then assume routing is not an issue here .

I have not used any DHCP Options  as the the IP helper method appears to be the recommendation when the DHCP/SCCM server sit on a different subnet .

Can you please assist ? 

Thanks in advance 

[jalejand]

Helpering in a fabric overlay (call it SDA, ACI, etc) with anycast gateways is useless unless the protocol has understanding of the real source of the relay (ex DHCP Opt 82).

There are two ways of achieving this:

1) Using DHCP Option 66 and 67
2) Using Proxy DHCP so the SCCM server acts as DHCP server (using unicast DHCP directly to the SCCM server, where options aren't needed).

But you seem to be having problems with the very initial DHCP of the PXE device; just wondering, is your fabric using collocated Border+CP or separated roles?

[HAT]

Hi Jalejand

Thanks for the reply , the fabric is collocated ( CP + Border ) . I have read that using DHCP options was not recommended so opted for IP helpers instead . 

PXE boot is  working on our Nexus based User Access network though but not on SDA .

I have changed the config by removing the SCCM server IP address  from the SVI config on the Fabric Edge and configured the DHCP server with the SCCM server IP address as the next server , also used Options 60 which seemed to have got me further by obtaining an IP address from the DHCP  server  but failed to download the NBP file ( Please see attachment ) .

DHCP server config

ip dhcp pool Desktop-Build
network 10.223.7.0 255.255.255.0
next-server 172.28.86.174            <------------  SCCM Server    
domain-name xxxx-xx.xxxx.loc
dns-server 172.28.64.10 172.28.65.10
default-router 10.223.7.1
option 60 ascii "PXEClient"
lease 0 8

Any assistance would be greatly appreciated 

Thanks 

[andy!doesnt!like!uucp]

i'm pretty sure your PXE-devices denies image it downloads by tftp in the PXE-stage