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kb:dhcp_relay_in_cisco_router

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Note DHCP relay does require the dhcp service to be running.

Eg below, where 192.0.0.3 is the DHCP server:

service dhcp
interface Vlan10
description HQ Staff Network
ip address 192.0.1.254 255.255.255.0
ip helper-address 192.0.0.3
!
interface Vlan50
description Wireless Vlan
ip address 192.0.5.254 255.255.255.0
ip helper-address 192.0.0.3

Using the DEBUG IP DHCP SERVER PACKET command, we can see what happens when a client device makes a DHCP request for an IP address:

002121: *Apr 29 17:37:55.549: DHCPD: Reload workspace interface Vlan10 tableid 0.
002122: *Apr 29 17:37:55.549: DHCPD: tableid for 192.0.1.254 on Vlan10 is 0
002123: *Apr 29 17:37:55.549: DHCPD: client's VPN is .
002124: *Apr 29 17:37:55.549: DHCPD: using received relay info.
002125: *Apr 29 17:37:55.549: DHCPD: Looking up binding using address 192.0.1.254
002126: *Apr 29 17:37:55.549: DHCPD: setting giaddr to 192.0.1.254.
002127: *Apr 29 17:37:55.549: DHCPD: BOOTREQUEST from 0100.248c.6e62.52 forwarded to 192.0.0.3.
kb/dhcp_relay_in_cisco_router.1533778480.txt.gz ยท Last modified: 2018/08/09 11:04 by Dan Mundy