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Interior Gateway Routing Protocol (IGRP) was a Cisco-proprietary Distance-Vector (D-V) classful routing protocol - basically an improved version of RIPv1. Like other D-V protocols, each IGRP router periodically flooded its routing table, but it differed from RIP in two ways. First, RIP’s advertisement interval was thirty seconds but IGRP’s was ninety seconds, which allowed IGRP to scale to larger networks than RIP. Second, RIP used a simple hop count metric, but IGRP’s more sophisticated metric was based on minimum path bandwidth and total path delay, with options to include link reliability and interface loading.
“Traceroute” is a utility that’s commonly used when troubleshooting IP networks, but many network managers at the CCNA level and beyond aren’t really sure how it works or what you can do with it. One reason for this might be that, unlike most things in the IP world, there are no standards documents describing how “Traceroute” functions. Thus the implementations are vendor-specific, and not even the utilities’ names are standardized. With Cisco IOS and Unix, it’s called “traceroute”, in the Microsoft world, it’s “tracert”, and other operating systems have similar utilities, such as “tracepath” for Linux.
When the hostname.domainname associated with my Small Office Home Office (SOHO) failed to update after a power outage, and a new DHCP-assigned external address was assigned to my router, I was reminded of the need for Dynamic DNS. This article will explore the implem...
As is frequently the case these days, I get a brainstorm for an article during a Cisco Security training class I conduct. This summer I taught the Securing Networks with ASA Fundamentals class, which concentrates heavily on the Adaptive Security Device Manager (ASDM)...
Ever seen a /32 prefix in the IP routing table? A /32 prefix is commonly referred to as a host route since it identifies a route to a specific IP host address. Since most (but not all) host computers don't run routing protocols, we could create a host route on a rou...
No matter which IT field you're working in, there are several skills that are useful for every IT professional to know. Here, seven experienced IT professionals working in the networking, programming, project management, and security fields, share what they believe a...
As is sometimes the case, the idea for this article originated with a student question I received during one of the Securing Networks with ASA Fundamentals classes I have taught this summer. The course material mentions a simple scenario whereby IP Telephony traffic...
As any network administrator will tell you, the ASA Security appliance (as well as its forerunner, the PIX) are capable of generating massive amounts of log messages, especially when the firewall/security appliance is set to log messages at debug level to the syslog...
A feature common to IPSec Virtual Private Network implementations throughout the Cisco product line is Perfect Forward Secrecy (PFS). This optional additional component is now a default supplied configuration setting with the Adaptive Security Device Manager (ASDM) I...
Adding a new computer to an Active Directory domain can be a disruptive process, particularly if that computer is part of a large, high-speed deployment. Djoin.exe is a command line tool that permits the joining of a Windows 7 or Server 2008 R2 computer to Active Dir...