Category Archives: Labs

Networking: Blocking Access to a Website via Extended Access List [Video]

Posted on April 16, 2012 by Humair

This video demonstrates how to use an extended access list to prevent specific hosts from accessing a website. In this lab I use two Cisco 2811 routers [IOS 12.4(15)T1] and two Cisco 2950-24 switches [IOS 12.1(22)EA4].

Posted in Cisco, Labs, Networking, Technology | Tagged ACL, Cisco 2811, Cisco 2811 router, Cisco 2950, Cisco 2950-24, Cisco 2950-24 switch, Cisco switch, extended access list, Extended ACL, prevent hosts from accessing a website, prevent specific hosts from accessing a website, router | Leave a comment

EIGRP – Best Path Selection

Posted on March 27, 2012 by Humair

By default EIGRP uses bandwidth and delay of the line to determine the best path to a remote network. However, if desired, EIGRP can use a composite of four metrics: bandwidth, delay, reliability, and load. Maximum transmission unit (MTU) is … Continue reading →

Posted in Cisco, Labs, Networking, Protocols | Tagged bandwidth, Cisco, Cisco 3725, Cisco 3725 router, Cisco 3725 routers, delay, delay of the line, EIGRP, EIGRP calculation, eigrp load balancing, Enhanced Interior Gateway Routing Protocol, equal cost load balancing, load balancing, router, routing table, topology table | Leave a comment

EIGRP and OSPF Redistribution on Cisco Routers

Posted on February 7, 2012 by Humair

This was a quick lab I threw together which I thought was pretty cool. In this lab I use five Cisco 3725 routers [IOS 12.4(15)T10] in which I have two groups of routers each on a different subnet and running … Continue reading →

Posted in Cisco, Labs, Networking, Protocols, Technology | Tagged Cisco, Cisco 3725, Cisco 3725 router, cisco router, EIGRP and OSPF Redistribution, EIGRP Redistribution, EIRGP, OSPF, Redistribution, router | Leave a comment

Setup and Troubleshoot EIGRP

Posted on February 2, 2012 by Humair

I discussed Enhanced Interior Gateway Routing Protocol (EIGRP) briefly in a prior blog, Load Balancing with EIGRP, however, in this lab I use two Cisco 3725 routers [IOS 12.4(15)T10] to demonstrate how to configure EIGRP; additionally, I’ll discuss some useful … Continue reading →

Posted in Cisco, Labs, Networking, Protocols, Technology, Troubleshooting | Tagged Cisco, Cisco 3725, Cisco 3725 router, Cisco 3725 routers, dynamic routing, EIGRP, Enhanced Interior Gateway Routing Protocol, router | Leave a comment

Configuring PVST+ on Cisco Switches

Posted on February 1, 2012 by Humair

Per VLAN Spanning Tree Plus (PVST+) is a flavor of Spanning Tree Protocol (see prior blog, Default STP Behavior on Cisco Switches) which maintains a spanning tree instance for each VLAN in the network. This means certain VLAN trunks (using … Continue reading →

Posted in Cisco, Labs, Networking, Protocols, Technology | Tagged avoid loop, Cisco, Cisco 3560, Cisco 3560 switch, Cisco switch, dot1q, loop, Per VLAN Spanning Tree Plus, prevent loop, PVST+, Spanning Tree Protocol, STP, switch, vlan | 6 Comments

Default STP Behavior on Cisco Switches

Posted on January 31, 2012 by Humair

In a prior blog, Functionality of Layer 2 Switches/Bridges, I discussed the core functionality of layer 2 switches. In this blog, I hit upon the Spanning Tree Protocol (STP) used on layer 2 switches to prevent loops. As mentioned before, … Continue reading →

Posted in Cisco, Labs, Networking, Protocols, Technology | Tagged Blocking, BPDUs, bridge ID, Bridge Protocol Data Units, broadcast storm, change root bridge, Cisco, Cisco 3560, designated port, device priority, Disabled, Forwarding, layer 2, layer 2 loop, Learning, Listening, loop, MAC address, prevent layer 2 loop, prevent loop, redundancy, root bridge, root port, Spanning Tree Protocol, STP | 1 Comment

Cisco – Filtering Unwanted Packets with Standard Access Lists

Posted on January 7, 2012 by Humair

Access lists (ACLs) are basically statements that packets are compared against for the purpose of taking some action if a match occurs. After an access list is created, it can be applied to inbound or outbound traffic; in some cases … Continue reading →

Posted in Cisco, Labs, Networking | Tagged access list, access lists, acess-lists, ACL, ACLs, block host, block ip address, block packet, block traffic, Cisco, Cisco 2611, Cisco 2611 router, deny host, deny ip address, deny packet, deny traffic, extended access list, filter, filter host, filter ip address, filter packet, filter traffic, named access list, router, standard access list, standard access-lists | 1 Comment

OSPF Explained and Useful Troubleshooting Commands

Posted on January 4, 2012 by Humair

Open Shortest Path First (OSPF) is an open standard link-state routing protocol that supports multiple equal-cost routes to the same destination (four by default). OSPF constructs a shortest path tree and then updates the routing table with the best paths. … Continue reading →

Posted in Cisco, Labs, Networking, Protocols, Technology, Troubleshooting | Tagged ABRs, adjacency, area 0, Area Border Routers, AS, ASBR, Autonomous System, Autonomous System Border Router, backbone area, Backup Designated Router, BDR, Cisco, Cisco 2126XM, Cisco 2126XM router, Cisco IOS, cisco router, cost, Designated Router, Hello packets, Link State Advertisement, LSA, neighbor, Neighbors, Open Shortest Path First, OSPF, OSPF Adjacencies, OSPF area, OSPF Backup Designated Router, OSPF BDR, ospf cost, ospf database, OSPF Designated Router, OSPF Hello Packets, ospf neighbor, OSPF Neighbors, OSPF process, OSPF Router ID, ospf troubleshooting, router, Router ID, Shortest Path First, shortest path tree, SPF | 3 Comments

Setting-up DHCP with IP Helper-Address on Cisco Routers

Posted on December 29, 2011 by Humair

In a prior lab, Setting-up DHCP on Cisco Routers, I discussed how to setup a Cisco router as a DHCP server. In this lab, I use a DHCP server setup on one subnet to provide DHCP services to two different … Continue reading →

Posted in Cisco, Labs, Networking, Protocols, Technology | Tagged Cisco, Cisco 2126XM, Cisco 2126XM router, Cisco WS-C2950-24, Cisco WS-C2950-24 switch, configure DHCP, dhcp, DHCP broadcasts, dhcp configuration, Dynamic Host Configuration Protocol, ip helper, ip helper-address, Setting-up DHCP with IP Helper-Address on Cisco Routers | 1 Comment

Setting-up DHCP on Cisco Routers

Posted on December 11, 2011 by Humair

The Dynamic Host Configuration Protocol (DHCP) provides the capability to automatically allocate reusable network addresses and configuration options to hosts.

Posted in Cisco, Labs, Networking, Protocols, Technology | Tagged BOOTP, Cisco, Cisco 2126XM, Cisco 2126XM router, cisco dhcp configuration, cisco router, cisco setup dhcp, Cisco switch, Cisco WS-C2960-24TT, Cisco WS-C2960-24TT switch, dhcp, dhcp configuration, Dynamic Host Configuration Protocol, router, switch | 1 Comment