The ranting of an IT Professional » IOS

Setting up DHCP relay on a Cisco router

Jason Tramer — Tue, 14 Jul 2009 14:41:14 +0000

This came up for me recently. Here are the commands to setup DHCP relay on a Cisco router, it’s super easy if you know what to do.

The interface you are configuring is the interface where the DHCP clients are located. The helper-address is the IP address of your DHCP server, in this case 10.10.0.5. Please note you will need to make this configuration change on EVERY interface that has clients that will need to access the DHCP server.

router2# conf t
router2(config)# int e0
router2(config-if)# ip helper-address 10.10.0.5

Cisco Router – Upload and IOS image from ROMMON mode

Jason Tramer — Tue, 07 Jul 2009 20:23:39 +0000

If you ever delete your IOS image and the system reboots before you get the new one on or if you upload the image and it is corrupt you will need to know how to upload an image from ROMMON mode.

Here are a sample of the commands, replace the entries with your specifics:

rommon 1 > IP_ADDRESS=192.168.1.5
rommon 2 > IP_SUBNET_MASK=255.255.255.0
rommon 3 > DEFAULT_GATEWAY=192.168.1.1
rommon 4 > TFTP_SERVER=192.168.1.10
rommon 5 > TFTP_FILE=c2600-adventerprisek9-mz.124-5a.bin
rommon 6 > tftpdnld (this command kicks off the tftp download)