The Relay receives replies from the servers and forwards them back to the originating client.įigure 3-12 Reference Topology for Analysis of DHCP Relay OperationĮxample 3-35 refers to the internetwork of Figure 3-12, where ASA relays DHCP packets from clients that reside on interface dmz (subnet 172.16.201.0/24) to the server 172.16.200.200, reachable through the outside interface. When acting as a DHCP Relay, a Layer 3 device (a router or a network firewall, for instance) converts broadcast packets from clients into unicast packets destined to a DHCP server located on a different subnet. ! The default route learned through DHCP is visible on the IOS routing tableĭMZ# show ip route | begin Gateway Gateway of last resort is 172.16.201.2 to network 0.0.0.0Ĭ 172.16.201.0 is directly connected, FastEthernet4.201įigure 3-12 represents a sample topology used for the investigation of the DHCP Relay feature. Lease: 3600 secs, Renewal: 1800 secs, Rebind: 3150 secs ! Displaying information about the DHCP lease on the IOS clientĭMZ# show dhcp lease Temp IP addr: 172.16.201.60 for peer on Interface: FastEthernet4.201ĭHCP Lease server: 172.16.201.2, state: 5 Bound Interface dmz, Configured for DHCP SERVER Interface outside, Configured for DHCP CLIENT ! Summary information about DHCP Services enabled on ASA ASA as DHCP Server and IOS as DHCP ClientĪSA5505# show running-config dhcpd dhcpd auto_config outside **auto-config from interface 'outside' **auto_config dns 172.16.250.250 **auto_config domain ĭhcpd address 172.16.201.60-172.16.201.69 dmz ! Viewing information about the DCHP Server function Interface IP-Address OK? Method Status Protocol ! The DHCP-learned default route becomes visible on ASA's routing tableĪSA5505# show route outside | begin Gateway Gateway of last resort is 172.16.200.200 to network 0.0.0.0Ĭ 172.16.200.0 255.255.255.0 is directly connected, outsideĭ* 0.0.0.0 0.0.0.0 via 172.16.200.200, outsideĪSA5505# show interface ip brief | include DHCP|Method
! ASA configured as a DHCP client on interface outsideĪSA5505(config-if)# ip address dhcp setroute
! Router "OUT" acts as DHCP Server for subnet 172.16.200.0/24 IOS as DHCP Server and ASA as DHCP Client Figure 3-11 Reference Topology for DHCP Server and DHCP Client Example 3-33.