Autoinstall - LAN

Autoinstall is a quite interesting topic, it deserves some labbing.

Start from the DOC-CD as usual, we focus on the LAN implementation first.

You can find HERE the flowchart of the autoinstall process.

This guide is quite clear too:

AutoInstall Using DHCP for LAN Interfaces

This is the topology we’ll use:

autoinstall_cisco

R1 and R2 will start without configuration.

R3 is the DHCP server that provides TFTP informations to R1 and R2.

R4 acts as TFTP server that stores the configurations

First step: configure DHCP pool on R3:

ip dhcp pool R1 host 10.0.123.1 255.255.255.0 client-identifier 0063.6973.636f.2d63.3230.302e.3636.6262.2e30.3030.302d.4661.302f.30 option 150 ip 4.4.4.4 option 67 ascii R1-confg default-router 10.0.123.3 

Do you prefer an easier client identifier? Read THIS blog post from Ivan Pepelnjak.

The pool defines a reserved IP address to be assigned to R1. We provide a default router and a couple of options. Option 150 defines a TFTP server, option 67 defines the filename do look for.

Second step: configure R4 as TFTP server

R4(config)#tftp-server flash:R1-confg

The config file for R1 is stored in R4’s flash.

Now we erase the configuration on R1 and reload it:

R1#erase startup-config Erasing the nvram filesystem will remove all configuration files! Continue? [confirm] [confirm] [OK] Erase of nvram: complete R1#reload

R1 starts without a config file, requests an IP address via DHCP:

*Mar 1 00:00:29.735: AUTOINSTALL: FastEthernet0/0 is assigned 10.0.123.1

Together with the IP address, R1 gets some options, so it looks for the TFTP server 4.4.4.4:

*Mar 1 00:00:29.739: AUTOINSTALL: Obtain tftp server address (opt 150) 4.4.4.4

The option 67 informs R1 to download the config file R1-confg:

*Mar 1 00:00:49.291: %SYS-5-CONFIG_I: Configured from tftp://4.4.4.4/R1-confg by console

We can see the TFTP request on R4:

R4# Mar 2 23:20:14.226: TFTP: Looking for R1-confg Mar 2 23:20:14.230: TFTP: Opened flash:R1-confg, fd 0, size 1989 for process 244 Mar 2 23:20:14.374: TFTP: Finished flash:R1-confg, time 00:00:00 for process 244

This is the capture of the request coming from R1 to R4:

autoinstall_1

We can have the same result using option 66 “Server-Name” instead of option 150. We must provide a DNS server via DHCP.

Let’s do it using R2 as DHCP client. Create DHCP pool on R3:

ip dhcp pool R2 host 10.0.123.2 255.255.255.0 client-identifier 0063.6973.636f.2d63.3230.312e.3636.6262.2e30.3030.302d.4661.302f.30 default-router 10.0.123.3 option 66 ascii tftp.ifconfig.it option 67 ascii R2-confg

We configure R3 as DNS server too:

R3(config)#ip host tftp.ifconfig.it 4.4.4.4 R3(config)#ip dns server

Now we can erase startup-config and reload R2.

On R2:

Translating "tftp.ifconfig.it"...domain server (255.255.255.255) [OK] Loading R2-confg from 4.4.4.4 (via FastEthernet0/0): ! [OK - 1923 bytes] *Mar 1 00:00:16.863: AUTOINSTALL: FastEthernet0/0 is assigned 10.0.123.2 *Mar 1 00:00:16.863: AUTOINSTALL: Obtain tftp server name tftp.ifconfig.itresolved to 4.4.4.4 *Mar 1 00:00:26.459: %SYS-5-CONFIG_I: Configured from tftp://tftp.ifconfig.it/R2-confg by console

On R4:

Mar 1 00:25:26.647: TFTP: Looking for R2-confg *Mar 1 00:25:26.651: TFTP: Opened flash:R2-confg, fd 0, size 1923 for process 245 *Mar 1 00:25:26.719: TFTP: Finished flash:R2-confg, time 00:00:00 for process 245

Everything worked as expected.

DHCP options are assigned by IANA, full list HERE.

How to use the mac address as client-id is explained HERE on ioshints blog. There’re plenty of posts aboutDHCP.

 
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