chapter 1 ccna 3

chapter 1 ccna 3.IOS(config)# . IP source routing: similar to token ring source routing, based onIOS(config)# source address to select the path to the destination network..Finger: Used to collect account information on the machine. Finger is enabled by default on IOS routers. the command no service finger has been replaced by the command no ip finger.. Small servers (smallserver): Programs with port numbers less than 20, such as Chargen, can be used by hackers to gain illegal access to the router or to launch DoS attacks (these servers are disabled by default in IOS 12.0 and later).0 For example, if the echo service is enabled, a hacker can send a forged DNS query with a DNS server as the source address and a router as the destination address; the router receives such a query. The destination address is the router; when the router receives such a query, it will respond to the DNS server, which allows the hacker to bypass internal filters that would otherwise discard UDP DNS queries..CDP: Cisco-specific protocol used to share basic hardware and software information with connected Cisco devices; enabled by default on all interfaces of IOS devices (discussed in Chapter 6) o.BootP: available for Cisco routers to use to obtain IOS images on the BootP server; enabled by default.. Auto-load configuration: the command no service config disables the router from looking up the configuration on the TFTP server; the command no boot network disables the router from loading an IOS image from the TFTP server.. DNS lookup: enabled by default, sent to address 255.255.255.255o To globally disable DNS lookup, use the command no ip domain-lookup; to manually specify a DNS server, use the command ip name-server.. TCP Survival: Enable this to verify that sessions are still open and to prevent "orphaned" sessions. The router will delete sessions that no longer exist.DHCP: Unless the router is the only device that can provide IP addressing information to hosts (as is often the case in branch offices), its DHCP server feature should be disabled. DHCP is discussed in Chapter 7.