As I get a lot of hits from Google refering to local login, here's the whole story: Cisco IOS supports local username/password based authentication (almost) forever (it's been there even before the AAA architecture). To change from simple password-based authentication to username+password based on, use login local configuration command on console and/or VTY lines. The local usernames and passwords are defined with the username configuration command.

Update 2012-08-27: Stefan de Kooter reported the bug had been fixed in IOS release 15.1(4)M.

If you run multiple web sites on a single physical server, it's highly likely that you rely on the ability of HTTP/1.1 clients to specify the Host: field in the HTTP request to indicate which web site they're trying to access.

Cisco IOS always inserts the web server's IP address (not the hostname) in the Host: field of the HTTP request, regardless of whether you enter IP address or hostname in the URL part of an IOS command that supports HTTP (for example, copy or more command) ... and regardless of whether the hostname is locally configured with the ip host command or resolved by an external DNS server specified in the ip name-server command.

In a previous post, I've shown how you can log the changes in interactive user's privilege level. With the Cisco IOS Login Enhancements (introduced in IOS release 12.3(4)T, integrated in 12.4), you can also log all login successes and failures, even when using local user database (a similar functionality was previously achievable only when using central TACACS+ or RADIUS server).

The configuration commands to enable terminal access logging are login on-success log and login on-failure log. You can also specify that you want send SNMP traps in these circumstances (with the trap option) or that you only want to log every Nth attempt with the every n option.

The logging userinfo configuration command introduced in IOS release 12.3T (integrated into 12.4) starts logging of all changes in user privilege levels (as requested by enable or disable commands).

When I was still teaching Cisco courses, we were telling the students that the order of network statements in an OSPF process was important if their ranges were overlapping; the first network statement that matched an interface IP address would place that interface in the corresponding area. This is no longer true; Cisco IOS now properly handles overlapping network area configuration commands.

Consider the following example:

Cisco Press has just released my latest book (and my first digital one): Deploying Zone-Based Firewalls. The book covers a completely new way to configure IOS firewall feature set based on security zones you define on a router and inter-zone policies configured using the familiar class-maps and policy-maps.

You can preview this digital book (they call it Digital Short Cut) using the Safari technology at Cisco Press and buy it at Amazon.

I always hate it when Cisco IOS asks me for things I've already supplied in a command line, the most notable case being the copy command. For example, if you supply the complete source and destination file name in the command line, IOS still insists on asking you all the same questions (at least filling in the parameters I've supplied in the command line):

As part of Configuraton Change Notification and Logging feature, Cisco IOS stores the most recent configuration commands in a circular buffer and (optionally) sends them to syslog streams.

This feature is configured under the archive configuration mode with the log config command, which brings you to yet another configuration mode where you can fine-tune the parameters (they are obvious, on-router help is sufficient), for example:

archive
 log config
  logging enable 100
  notify syslog
  hidekeys

After you've enabled configuration command logging, you can use the show archive log config all command to inspect the logging buffer. You can also display commands entered in a particular session or by a selected user.

The Cisco IOS’s AAA architecture contains many handy features, including authorizing and logging every CLI command executed on the router. Unfortunately, the AAA command accounting only supports TACACS+ as the AAA transport protocol, making it unusable in RADIUS environments.

You can use Embedded Event Manager as a workaround. The following configuration commands will log every command executed on the router.

Although a bit outdated (and discussing older Cisco IOS releases), the article Cisco IOS from an Attacker's Point of View is still very relevant, as most vulnerabilities discussed in it arise from unsecure router configuration. Highly recommended reading!