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Unicast. or Broadcast for DHCP relay agent?

From the doucment,

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a00800f0804.shtml

the DHCPOFFER and DHCPACK packet from relay agent to client should be broadcast. But when I use the debug ip dhcp server packet and debug ip packet, I found the packets are unicast.

Nov 16 14:20:21.790 UTC: datagramsize=343, IP 0: s=0.0.0.0 (Vlan200), d=255.255.255.255, totlen 329, fragment 0, fo 0, rcvd 2

Nov 16 14:20:21.790 UTC: UDP src=68, dst=67

Nov 16 14:20:21.790 UTC: DHCPD: setting giaddr to 61.145.158.1.

Nov 16 14:20:21.790 UTC: datagramsize=301, IP 63100: s=61.145.158.1 (local), d=61.144.232.9, totlen 329, fragment 0, fo 0, cef process switched

Nov 16 14:20:21.790 UTC: UDP src=67, dst=67

Nov 16 14:20:21.790 UTC: datagramsize=301, IP 63100: s=61.145.158.1 (local), d=61.144.232.9 (Vlan3), totlen 329, fragment 0, fo 0, sending

Nov 16 14:20:21.790 UTC: UDP src=67, dst=67

Nov 16 14:20:21.790 UTC: datagramsize=375, IP 63100: s=61.145.158.1 (local), d=61.144.232.9 (Vlan3), totlen 329, fragment 0, fo 0, sending full packet

Nov 16 14:20:21.794 UTC: UDP src=67, dst=67

Nov 16 14:20:21.794 UTC: DHCPD: BOOTREQUEST from 0100.e04c.7758.d2 forwarded to 61.144.232.9.

Nov 16 14:20:21.794 UTC: DHCPD: BOOTREQUEST not forwarded. No route to helper addr 61.144.232.9

Nov 16 14:20:22.154 UTC: datagramsize=342, IP 5131: s=61.144.232.9 (Vlan3), d=61.145.158.1, totlen 328, fragment 0, fo 0, rcvd 4

Nov 16 14:20:22.158 UTC: UDP src=67, dst=67

Nov 16 14:20:22.158 UTC: DHCPD: forwarding BOOTREPLY to client 00e0.4c77.58d2.

Nov 16 14:20:22.158 UTC: DHCPD: creating ARP entry (61.145.158.89, 00e0.4c77.58d2).

Nov 16 14:20:22.158 UTC: DHCPD: unicasting BOOTREPLY to client 00e0.4c77.58d2 (61.145.158.89).

Nov 16 14:20:22.158 UTC: datagramsize=300, IP 63102: s=61.145.158.1 (local), d=61.145.158.89, totlen 328, fragment 0, fo 0, cef process switched

Why the result is different from the doucment, and how the router can know the BOOTREPLY should be sent to the client (00e0.4c77.58d2) if it doesn't look into the content of the DHCP packet.

1 REPLY
Cisco Employee

Re: Unicast. or Broadcast for DHCP relay agent?

I have forwarded your request on to our SME (Subject Matter expert) to review the doc and your request.

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