Chapter 5: Using AutoInstall
August 1997 Page 5-5
2524UM
How AutoInstall Works Once the requirements for using AutoInstall are met, the dynamic con-
figuration of the new router occurs in th is or der:
1. The new router acquires its IP addre ss. Depending on the interface
connection between the two routers and/or acces s servers, the new
router's IP address is dynamically resolved by either SLARP re-
quests or BOOTP or RAR P requests.
2. The new router resolves its name through network-confg, cisco-
net.cfg, or DNS.
3. The new router automatically requests and downloads its configu-
ration file from a TFTP server.
4. If a host name is not resolved, the new router attempts to load
router-confg or ciscortr.cfg.
Acquire the New Router's IP Address
The new router (newrouter) resolves its interface's IP addresses as:
zIf newrouter is connected by an HDLC-encapsulated serial line to
the existing router (existing), newrouter sends a SLARP request to
existing.
zIf newrouter is connected by an Ethernet, T oken Ring, or FDDI in-
terface, it broadcasts BOOTP and RARP r equests.
zIf newrouter is connected by a Fr am e Relay-encapsulated serial
interface, it first attempts the HDLC automatic installation process
and then attempts the BOOTP or RARP process over Ethernet,
Token Ring, or FDDI. If both attempts fa il, the new router at-
tempts to automatically install over Frame Relay. In this case, a
BOOTP request is sent over the lowest numbered serial or HSSI
interface.
The existing router (existing) responds in one of these ways depending
on the request type:
zIn response to a SLARP request, existing sends a SLARP reply
packet to newrouter. The reply packet contains the IP address and
netmask of existing. If the host portion of the IP address in the
SLARP response is 1, newrouter configures its interf ace using the
value 2 as the host portion of i ts IP address and vice versa. (See
Figure 5-1.)