Author Archive

Time-Based ACLs

Written by admin. Posted in ACLs

Time-bases ACLs are Access Lists that enable you to restrict or allow resources based on time periods. For example you as a network administrator are asked to restrict web browsing to some particular servers during working hours. To implement  an time based access lists there are few simple steps:


IP address classes – IPv4

Written by admin. Posted in Cheat Sheets

IPv4 addresses are 32 bit addresses divided into 4 octets. In this article we’ll examine how IP addresses are divided into classes and what are they used for. Classful allocation of IP address space wasted many addresses, which exhausted the availability of IPv4 addresses. Today is used  classless addressing system.



Written by admin. Posted in Cheat Sheets

Deep understanding of OSPF Link State Advertisments (LSAs) is crucial to understand OSPF behavior. LSAs build up the OSPF link state database (LSDB), and they are exchanged between OSPF enabled nodes. Here you have the list of OSPF LSAs and a short description.


Routing Protocols Timers

Written by admin. Posted in Cheat Sheets

Any routing protocol makes use of timers. They can be hello timers, dead/hold-down timers and so on. On this page you will find default timers values for various routing protocols.


Administrative Distance

Written by admin. Posted in Cheat Sheets

Administrative Distance is reliability assigned by routers to a routing protocol. When a router learns the same route from different routing protocols, then the route learned from protocol with the lowest Administrative Distance (AD) is preferred over the others. For example the router learns a route to via OSPF and via RIP, then the one learned via OSPF is the preferred one.