Configure Cisco router as DHCP client
Remember, SOHO devices are configured as DHCP clients by default. When you are DHCP client to your ISP you need to configure interface on enterprise device to receive IP address.
I have created topology as it is shown in Slide 1.
Slide 1.
ISP router is configured as DHCP for 192.168.100.0/24 network with 192.168.100.1 on Fa0/0.
On ISP_Client router you need to enable Fa0/0 to be DHCP client. Please, configure your router as follows:
ISP_Client(config)#interface FastEthernet0/0
ISP_Client(config-if)#ip address dhcp
First verify that you recieved IP address with show ip interface brief. My output looks like this:
ISP_Client#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.100.2 YES DHCP up up
FastEthernet1/0 unassigned YES unset administratively down down
FastEthernet1/1 unassigned YES unset administratively down down
GigabitEthernet2/0 unassigned YES unset administratively down down
Notice that we have IP address on FastEthernet0/0. Now verify your routing table with show ip route:
ISP_Client#show ip route
Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2
i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2
ia – IS-IS inter area, * – candidate default, U – per-user static route
o – ODR, P – periodic downloaded static route, H – NHRP, l – LISP
+ – replicated route, % – next hop overrideGateway of last resort is 192.168.100.1 to network 0.0.0.0
S* 0.0.0.0/0 [254/0] via 192.168.100.1
192.168.100.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.100.0/24 is directly connected, FastEthernet0/0
L 192.168.100.3/32 is directly connected, FastEthernet0/0
Along with IP address you will “receive” default route to your ISP.
