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  • Table of Contents
  • Layer 2 Technologies
    • Ethernet Switching
      • L2 Switch Operations
      • Spanning Tree
        • 802.1d – STP
        • 802.1w – RSTP
        • 802.1s – MSTP
      • VTP 101
      • Private VLANs
      • VLANs
      • EtherChannel 101
    • Layer 2 WAN Protocols
      • HDLC
        • HDLC 101
      • PPP
        • PPP 101
        • PPP Authentication - PAP
        • PPP Authentication – CHAP
        • PPP Authentication – EAP
        • PPP Multilink
        • PPPoFR – PPP over Frame Relay
        • PPPoE – PPP over Ethernet
      • Frame Relay
        • Frame Relay 101
        • Frame Relay 102
        • Frame Relay Encapsulations – IETF vs Cisco
        • Multilink Frame Relay
        • Frame Relay Switching
        • Routing over Frame Relay
      • Bridging
        • Bridging on a router
        • MTU 101
    • Wireless
      • Wireless Principles
      • Wireless Implementations
      • Wireless Roaming
      • Wireless Authentication
        • WPA2 PSK
        • WPA2 802.1X
  • IPv4
    • IPv4 Addressing
      • Backup Interfaces
      • FHRP 101
      • DHCP 101
      • DNS 101
      • ARP 101
      • IPv4 101
      • Tunnel Interfaces
        • GRE Tunnels
      • BFD – Bidirectional Forwarding Detection
    • IPv4 Routing
      • How the routing table is built
        • How CEF works
        • Routing Order of Operations
        • NSF – Non Stop Forwarding
      • RIP
        • RIP 101
      • EIGRP
        • EIGRP 101
        • EIGRP Metric
        • More EIGRP Features
      • OSPF
        • OSPF 101
        • OSPF Areas
        • OSPF LSAs
        • OSPF Mechanics
      • IS-IS
        • IS-IS 101
        • IS-IS Mechanics – CLNP
      • BGP
        • BGP 101
        • BGP Attributes
        • More BGP
      • Route Redistribution
      • Policy based Routing
      • PfR 101 – Perfromance Routing
      • ODR
  • IPv6
    • IPv6-101
    • IPv6 Routing
    • Interconnecting IPv6 and IPv4
  • MPLS
    • MPLS 101
    • MPLS L3 VPN
  • Multicast
    • Multicast 101
    • PIM 101
    • IGMP 101
    • Inter Domain Multicast
    • IPv6 Multicast
    • Multicast features on switches
  • Security
    • NAT 101
    • NAT for Overlapping Networks
    • ACLs 101
    • ACLs 102
    • Cisco IOS Firewall
    • Zone Based Firewall
    • AAA 101
    • Controlling CLI Access
    • Control Plane
    • Switch Security
      • Switchport Traffic Control
      • Switchport Port Security
      • DHCP Snooping and DAI
      • 802.1x
      • Switch ACLs
    • IPSec VPN 101
      • IKE / ISAKMP 101
      • IPSEC Crypto Maps 101
      • IPSEC VTI 101
      • DMVPN 101
    • EAP 101
  • Network Services
    • NTP 101
    • HTTP 101
    • File Transfer 101 – TFTP & FTP
    • WCCP 101
  • QoS
    • QoS 101
    • Classification and Marking
    • Congestion Management
      • Legacy Congestion Management
      • SPD – Selective Packet Discard
      • CBWFQ
      • IP RTP Priority
    • Congestion Avoidance – WRED
    • Policing and Shaping
      • CAR 101
    • Compression and LFI
      • Header and Payload Compression
      • LFI for MultiLink PPP
    • Frame Relay QoS
      • Per VC Frame Relay QoS
    • RSVP 101
    • Switching QoS
  • Network Optimization
    • NetFlow 101 – TNF – Traditional NetFlow
    • NetFlow 102 – FNF – Flexible NetFlow
    • IP SLA 101
    • IP Accounting 101
    • Logging 101
    • SNMP and RMON 101
    • Cisco CLI Tips and Tricks
    • AutoInstall
    • Enhanced Object Tracking
    • Troubleshooting 101
    • SPAN, RSPAN, ERSPAN
  • Network Architecture
    • Hierarchical Network Architecture
    • SD Access
    • SD WAN
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  • AutoInstall Process
  • Assign IP Address
  • Get Config Files

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  1. Network Optimization

AutoInstall

PreviousCisco CLI Tips and TricksNextEnhanced Object Tracking

Last updated 3 years ago

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AutoInstall Process

The autoinstall process discribed in the following paragraphs is used in autoconfiguration of a clean router (no config) over an IP network. The following flowchart best describes this process

Here are some details about the AutoInstall steps:

Assign IP Address

The first step in the AutoInstall process is for the router to receive an IP Address. The method used differs according to the the encapsulation of its interfaces.

Ethernet – DHCP

On Ethernet interfaces, a router will send DHCP requests in order to receive an IP Address. Depending on the network architecture, the DHCP server might be on the same network segment and no additional configuration is required, or it might be on a different network segment. In the last case, the directly connected router (Staging Router) should forward the DHCP requests to the remote DHCP server via the ip helper-address command.

HDLC – SLARP

On Serial interfaces with HDLC encapsulation, a router will send a SLARP (Serial Line ARP) request in order to find its IP Address. On the other end of the serial interface, the Staging Router must be configured with the 1st or the 2nd IP Address of the subnet.For example:

192.168.0.1/24 or 192.168.0.2/24
172.16.10.5/30 or 172.16.10.6/30

If the router is configured with one of these 2 addresses, then it will send a SLARP Reply with the other address back to the AutoInstalling Router. The router will then use this address on the HDLC interface. Take care that when using serial interfaces, only the first Serial interface can be used for AutoInstall (Serial 0 or Serialx/0).

Frame Relay – BOOTP

On Frame Relay interfaces, a router will send BOOTP requests in order to find its IP Address. The router on the other end of Frame Relay connection will reply with the IP Address configured in the static map for that particular DLCI:

R(config-if)# frame-relay map ip IP-ADDR DLCI

Again, only the first Serial interface can be used for AutoInstall (Serial 0 or Serialx/0).

Get Config Files

After the router found its IP Address, it now must find its hostname and get appropriate configuration files.

Finding Hostname

After receiving its IP Address, a router will try to find its hostname. On Ethernet networks, it could get the address of the DNS server via DHCP. If it gets that address then it will try to do a reverse DNS lookup to find its hostname. If the DNS server is not on the same subnet, the directly connected router should be configure with an ip helper-adddress. Another option is for the router to request a specific file that contains IP to HOSTNAME mappings via TFTP. The address of the TFTP server could be sent to the router via DHCP Option 150. If not, the router will use the address 255.255.255.255 to reach any TFTP server on the subnet. If the TFTP server is on another subnet, the directly connected router should be configure with an ip helper-adddress. The router will request the file network-config or cisconet.cfg from the TFTP server, in this order. This file should have a list of entries in the format:

ip host IP-ADDR HOSTNAME

The router will use the HOSTNAME from the entry with its IP-ADDR received via AutoInstall.

Hostname Specific Config

When it knows its hostname, the router will request another config file from the TFTP server. This config file should be host specific. The router will first request HOSTNAME-confg and then HOSTNAME.cfg files (replace HOSNTAME with the actual router host name). On Ethernet networks, another config file can be specified via DHCP Option 67.

Default Config

If the router was not able to find its hostname, it will attempt to get a default config file that should have enough information so that it could be accessed remotely and configure appropriately. The router will first request a file called router-confg and then router.cfg Again, on Ethernet networks, another config file can be specified via DHCP Option 67.

Autoinstall Flow Chart – © Cisco Configuration Guides – cf_12_4t_book.pdf