Specific Recommendations: Router Access
1. Shut down unneeded services on the router. Servers that are not running cannot break. Also, more memory and processor slots are available. Start by running the show proc command on the router, then turn off clearly unneeded facilities and services. Some servers that should almost always be turned off and the corresponding commands to disable them are listed below.
Small services (echo, discard, chargen, etc.)
no service tcp-small-servers
no service udp-small-servers
BOOTP - no ip bootp server
Finger - no service finger
HTTP - no ip http server
SNMP - no snmp-server
2. Shut down unneeded services on the routers. These services allow certain packets to pass through the router, or send special packets, or are used for remote router configuration. Some services that should almost always be turned off and the corresponding commands to
disable them are listed below.
CDP - no cdp run
Remote config. - no service config
Source routing - no ip source-route
3. The&interfaces on the router can be made more secure by using certain commands in the Configure Interface mode. These commands should be applied to every interface.
Unused interfaces - shutdown
No Smurf attacks - no ip directed-broadcast
Mask replies - no ip mask-reply
Ad-hoc routing - no ip proxy-arp
4. The console line, the auxiliary line and the virtual terminal lines on the router can be made more secure in the Configure Line mode. The console line and the virtual terminal lines should be secured as shown below. The Aux line should be disabled, as shown below, if it is not being used.
Console Line - line con 0
exec-timeout 5 0
login
Auxiliary Line - line aux 0
no exec
exec-timeout 0 10
transport input none
VTY lines - line vty 0 4
exec-timeout 5 0
login
transport input telnet ssh
5. PassWords can be configured more securely as well. Configure the Enable Secret password, which is protected with an MD5-based algorithm. Also, configure passwords for the console line,the auxiliary line and the virtual terminal lines. Provide basic protection for the user and line passwords using the service passwordencryption command. See examples below.
Enable secret - enable secret 0 2manyRt3s
Console Line - line con 0
password Soda-4-jimmY
Auxiliary Line - line aux 0
password Popcorn-4-sara
VTY Lines - line vty 0 4
password Dots-4-georg3
Basic protection - service password-encryption
6. Consider adopting SSH, if your router supports it, for all remote administration.
7. Protect your router configuration file from unauthorized disclosure.