So next-server in your dhcpd config is pointing to the IP address of the maas server? If it's not then PXE doesn't know where to retrieve pxelinux.0 (tftp server), also I don't see that pxe file name in your output either. Go back to the docs and verify that your DHCP server config is setup correctly according to your environment e.g. maas owns the network or using an existing dhcp server. It's also helpful for only one interface on your maas clients to acknowledge PXE boot.
If you have that all sorted see: http://www.networkingblog.in/ios-dhcp-pxe-and-ip-helper-address-5363
"Kumar April 13, 2010 at 6:53 am
I think your PXE clients are using MTFTP which uses Multicast. Again this traffic wont be forward using helper-address as its not a broadcast. ITs a multicast. YOu will need to enable multicast forwarding on your router to forward this multicast TFTP traffic to the PXE server which holds the bootfile. It works in the adjacent vlan, as the clients are on the same LAN as the PXE server. Can you put a sniffer such as ethereal and filter multicast packets and see what Multicast packet on port 69 is used (TFTP). THen you can enable PIM routing to forward multicast traffic from this vlan to the PXE server vlan.
Here is a guide to multicast routing.
Here is a link to ethereal – download."
Has PXE boot ever worked on your network before?