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This page provides the technical background about how ClickStart works. In most cases, you do not need to understand the technical background in order to use ClickStart. This background information is provided primarily for network administrators.
When using a web browser to configure a router, there are two broad issues:
When using a web browser to configure a router, the trickiest part is the initial configuration because the router does not yet have an IP address. Traditionally, initial router configuration is done withprotocols such as BOOTP or DHCP and their corresponding server programs. Using thse protocols works when the people configuring the router have moderate computer and networking expertise. In fact, the router can use BOOTP to get an initial IP address, and Windows NT has a DHCP server. However, ClickStart is designed for people who do not have the expertise and servers to use the traditional configuration methods.
When a router without a configuration file starts up, the Cisco IOS software listens on Ethernet interface 0 for a DNS request to the name new-router.cisco.com. This name is reserved within Cisco for initial router configuration. No system will ever have this name, and name servers do not respond to requests for this name, not even with a Name Error response.
When the Cisco 700-IOS software receives the DNS request for new-router.cisco.com, the request contains the IP address of the PC that issued the DNS request. The Cisco 700-IOS software then uses ARP to probe for an unused IP address near the PC's IP address, staying within likely subnet boundaries. If a machine responds to the ARP probe, the Cisco 700-IOS software tries the next IP address. If, after several tries, there is no response to an ARP probe, the Cisco IOS software uses that address as the IP address of the router. The software sends a DNS reply to the PC toanswer the DNS request for new-router.cisco.com with the address it just found.
The IP address discovery process presents some possible problems:
255.255.255.255. If the PC is configured with a different DNS server address, it will send an ARP request for the IP address before it sends the DNS request. If there is no local DNS server, which is a likely situation, no machine will answer the ARP request and the PC will never send the DNS request.
new-router.cisco.com and will send a Name Error response, probably before the Cisco 700-IOS sofware can locate an available address using ARP probes. The web browser will report that it could not find an IP address for new-router.cisco.com. In this case, trying again from the browser sometimes works because the router will have finished its ARP probing and can respond promptly to the DNS request.
new-router.cisco.com, and if the router is restarted before the configuration is completed and the process is repeated, the web browser remembers the name-to-address mapping and the DNS request is not sent out again. The solution to this problem is to exit the browser and restart it. The PC's local DNS resolver should not remember the name-to-address mapping because the response sent by the Cisco 700-IOS software has a time to live (TTL) of only 30 seconds. Browsers typically cache mappings without honoring TTLs.
ClickStart translates the information you fill in on the EZ Setup form to a standard configuration template. The standard configuration assumes that you will dial only one destination and use PPP/CHAP or CPP static routing. It requires values for the following parameters:
hostname - Name of the router
remote-name - Name of the remote router (used by CHAP)
remote-number 1 - Telephone number to dial
remote-number 2 - Telephone number to dial
remote-mac address - Remote router mac address (used by CPP)
IP-address-idsn - IP address for the ISDN interface (used by CPP)
switch-type - Service provider switch type
isdn-spid1 - Service profile identifier number assigned by the ISDN server provider for the B1 channel
isdn-spid2 - Service profile identifier number assigned by the ISDN server provider for the B2 channel
ip-address - IP address of Ethernet interface
ip-mask - Address mask for Ethernet interface
mode-of-operation - Bridging or routing
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