Here is what you need to know with regards to the Configuration Register in Cisco IOS. All Cisco routers have a 16-bit software register in NVRAM. The default is for Cisco routers to load Cisco IOS from FLASH MEMORY and to look for and load the STARTUP-CONFIG file from NVRAM. Some Reference Stuff Here is […]
Configuration Register in Cisco IOS Explained Read More »
To save you time searching through thousands of documents and sometimes disjointed practices, here are some of our recommendations for securing Cisco routers. These practices can also be applied to other routers in general, though we provide no specifics for others. Security is always a concern to those who manage and configure routers. Every router
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We are often asked about ICMP, and how it should be managed on a network. We hope this How To will explain this protocol a little and provide some initial guidance. What is ICMP? The Internet Control Message Protocol (ICMP) is part of Layer 3, not Layer 4 TCP, and it’s not UDP. ICMP provides
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In this How To, we explain Cisco SNAT. Cisco SNAT allows two or more routers performing the NAT function as a group. This is really handy for redundancy purposes, and can be used in conjunction with Cisco’s HSRP function (click here to see how HSRP is configured). The NAT routers are going to exchange information
Stateful Network Address Translation (SNAT) Feature on Cisco IOS Routers Read More »
The Virtual Router Redundancy Protocol (VRRP) is a computer networking protocol that provides for automatic assignment of available Internet Protocol (IP) routers to participating hosts. This increases the availability and reliability of routing paths via automatic default gateway selections on an IP subnetwork. See RFC 5798. VRRP provides information on the state of a router,
VRRP Configuration on Cisco IOS Routers Read More »
This one is short and sweet. Is your traceroute responding with “* * *”, or did you enter 1000000000 for the number of extended pings? Easy – simply type CTRL-SHIFT-6 to break the process. That is the Control Key (hold down), the Shift Key (also hold down) and the “6” key – all at the
Stopping PING or TRACEROUTE on Cisco IOS Routers Read More »
Monitoring the traffic pattern on a network are essential in today’s network. If network administrators do stay on top of the traffic patterns, they may make crucial mistakes in network provisioning or design. With the Internet in a constant state of flux as new and hot applications emerge, this task becomes even more important. Another
Netflow Basic Operations in Cisco IOS Read More »
How many times have I received a router that has no operating system on it? Way to many!! You turn on the router and it comes up in ROM Monitor mode (ROMMON). There is a way to get the operating system on the router from ROMMON. Below, I have documented the procedure. Preparation Before starting
Upgrading IOS on a Cisco Router in ROMMON Mode Read More »
The order of operations is hard coded into Cisco IOS and tells the router how to process traffic according to the configuration of different router functions and features. While we cant’ make you think like a router, it is likely you have already picked up on some of these. When configuring features such as Network
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What is NBAR? NBAR is a powerful packet filtering/identification/firewall that you may already have installed on your Cisco router. For a list of what NBAR can detect look here. NBAR is also what we call Cisco’s “autopilot” for QoS. It has been in IOS since ver. 12.0 and has been continually updated with recognition of
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As we said in our basic ACL How To, ACL’s’ are vital to networking today. Everyone uses them, and proper usage is imperative. In this How To, we are going a little deeper into two ACL types: Intrastructure and Transit. We will discuss the two with examples and you will clearly understand the difference between
Access Control to Infrastructure (iACL) and Transit (tACL) Read More »
What is AAA? It stands for Authentication, Authorization, and Accounting. When it comes to network security, AAA is one of many features a network manager may use. Here is what each of these are used for and why you should care: Why every network admin should care about AAA Besides passing certification tests like the
AAA Usage in IOS Classic Read More »
This How To explains how to fix an annoying default behavior on Cisco IOS. Mistype a command on a Cisco router and the router thinks you just typed a hostname. This is often an annoying problem. For example: Router#shwoTranslating “shwo”…domain server (10.1.1.1) % Unknown command or computer name, or unable to find computer addressRouter# Here,
Stopping the Cisco Router from Trying to TELNET Read More »
This How To explains the fundamentals of configuring EIGRP. EIGRP is an advanced distance-vector routing protocol that is used on a computer network to help automate routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers, but Cisco converted it to an open standard in
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What happens if there is a system or user on a VLAN that is infected by malware or is deliberately running a scanning program? This can cause a massive amount of entries in the CAM Table of the switch. Think of the CAM table as the MAC address table. There is a certain limit of
CAM Table Overflow Attack Mitigation on Cisco Switches Read More »