#Cisco ios tftp server how to
#Cisco ios tftp server upgrade
#Cisco ios tftp server software
#Cisco ios tftp server series

However, do not trust the Cisco IOS default behavior hard-code these commands to ensure that they are disabled.ДЇinger is an old UNIX program to determine who is logged into a host. In most current versions of the Cisco IOS, TCP and UDP small servers are disabled. Router(config)# no service udp-small-serversДЄfter you have disabled the services, make sure that you test your configuration as shown earlier. Router(config)# no service tcp-small-servers To disable these services on your router, use the configuration in Example 4-5. Example 4-4 shows a sample of connecting to the time port. you can see from Example 4-3, a string of characters is repeated continuously. Basically, with chargen enabled, your device would process all this traffic, taking away CPU cycles from other processes, and then just discard the information.Д®xample 4-3 shows a connection being opened to a router with chargen enabled.

For instance, if you have chargen (TCP or UDP 19) enabled on your device, a hacker could send a flood of traffic to this port, creating a DoS attack such as Fraggle. Hackers sometimes can use these services to their advantage. All of the services are outdated: They were used a decade ago in UNIX environments to provide basic information such as the date and time (daytime, port 13), to test connectivity (echo, port 7), and to generate a stream of characters (chargen, port 19).

TCP and UDP small servers are services running on ports 19 and lower on a device. Globally Disabling CDPДЄs you can see from this example, after you have disabled CDP with the no cdp run command, you will want to verify that it has been disabled with the show cdp command. To globally disable CDP, use the configuration in Example 4-2.

#Cisco ios tftp server how to

I discuss how to disable CDP globally in this section, and I cover how to disable it on your interfaces later in the chapter. Therefore, I highly recommend that you disable CDP completely on your perimeter router, or at least on the interfaces that connect to public networks, such as your ISP or other sites that you connect to that are not part of your company's security umbrella. The likelihood of this is small because the hacker must be in the same broadcast domain to view the CDP multicast frame. However, a hacker can use CDP information during a reconnaissance attack. If you are having Layer 3 connectivity problems, you can see your neighbor's IP address without having to log into the neighbor. If you are receiving CDP information from a neighboring Cisco device, you can be assured that at least Layer 2 is functioning correctly. Normally, CDP is used to test data link layer (Layer 2) connections.

#Cisco ios tftp server software

IOS (tm) 4500 Software (C4500-J-M), Version 11.3.10,Д¬opyright (c) 1986-1997 by cisco Systems, Inc.ДЄs you can see in Example 4-1, the neighboring router, RouterA, has an IP address of 192.168.1.250, is a 4500, was advertising information from Ethernet0/1, and is running Cisco IOS 11.3.10. Interface: Ethernet0/0, Port ID (outgoing port): Ethernet0/1Д¬isco Internetwork Operating System Software Platform: cisco 4500, Capabilities: Router The interface from which the CDP multicast was sentД®xample 4-1 shows some of the information that you can see from a neighboring device. The hardware capabilities of your Cisco IOS device, such as routing, switching, or bridging The Cisco IOS software version running on your Cisco IOS device

#Cisco ios tftp server series

The hardware platform of the Cisco IOS device, such as a 2600 series router or a 2950 switch The name of your Cisco IOS device (configured with the hostname command) CDP messages are generated as multicasts and include the following information about your Cisco IOS device: The media types supported include ATM, Ethernet, FDDI, frame relay, HDLC, PPP, and token ring. The Cisco Discovery Protocol (CDP) is a Cisco-proprietary protocol used to share basic device information with another directly connected Cisco device. Never make any assumptions about what is or is not running on your router always assume the worst-case scenario and disable all services that you are not using. By disabling these services manually or with AutoSecure, you are protecting yourself from this kind of issue. A previous service that was disabled by default might be enabled (by default) in the new release.

#Cisco ios tftp server upgrade

Plus, you never know what might happen when you upgrade your Cisco IOS. Therefore, I take the more cautious approach and assume that the services are enabled. I make this recommendation because Cisco has the habit of sometimes enabling or disabling a service automatically in a specific software release. I highly recommend that you manually or dynamically (with AutoSecure) disable all services that you are not using.