Information Technology Blog (Archive)

Unlike OSPF, EIGRP supports only one type of authentication: MD5. To configure MD5 authentication, first you need to define a key chain, one or more key numbers and a key-string. Then you need to enable MD5 authentication on the interface with this key chain. To prepare the topology, we have this basic configuration, with other parameters left to default: R1 hostname R1 ! interface Loopback0  ip address 1.1.1.1 255.255.255.0 ! interface Serial0/0  ip address 10.1.1.1 255.255.255.0  clock rate 2000000 ! router eigrp 99  network 1.0.0.0  network 10.0.0.0  no auto-summary R2 hostname R2 ! interface Loopback0  ip address 2.2.2.2 255.255.255.0 ! interface Serial0/0  ip address 10.1.1.2 255.255.255.0  clock rate 2000000 ! router eigrp 99  network 2.0.0.0  network 10.0.0.0  no auto-summary With this configuration and interfaces in up/up state, we won't have any problems in establishing neighbor relationship between the two routers. No...

Bad news to all fellow CCNA students and candidates, effective 01/16/2012, CCNA Composite Exam (640-802) has increased to $295 ($45 increase) and both ICND1 (640-822) and ICND2 (640-816) to $150 each ($25 increase). Meanwhile, good news for all Cisco Networking Academy students and alumni, Packet Tracer 5.3.3 is now released and available for download. Go to the Academy website and login with your account and click the Packet Tracer image at the left panel. Packet Tracer version 5.3.3 is a maintenance release that fixes functional and technical issues in the previous versions. It replaces Packet Tracer version 5.3.2. Packet Tracer 5.3.3 supports activities authored in Packet Tracer 4.x, 5.0.x, 5.1.x, 5.2.x, and 5.3.x. Please note that the last two courses of the CCNA Discovery and CCNA Exploration curricula require Packet Tracer version 4.11 at a minimum, CCNA Security requires version 5.2 at a minimum, and the Packet Tracer Skills Based Assessments require version 5.3.2 at a...

I was going through my usual reading today, to be exact, Chapter 3: Troubleshooting LAN Switching of CCNA ICND2 Official Cert Guide 3rd Edition and I came across a text explaining the details of switch forwarding path. And then I just realized that I totally miscomprehend the idea of VLAN tagging. The proof is my previous post  explaining about the problem with Native VLAN.  Quoting what I've said: As I ping from PC1 which is in VLAN 20 to the switches which has management interface of interface VLAN 88, it has to go to R1 from the trunk link. The frame was supposed to be tagged with VLAN 88 but since we defined VLAN 88 on S2 as the Native VLAN, the frame is not tagged (no 802.1Q header). My idea is when a host has to send a frame to a host in another VLAN, the switch tags the frame with VLAN ID of the receiving host before forwarding it to the trunk link -- this is where I got it wrong.  What's right: When a switch receives a frame on a port (ass...

In this simple lab, my objective is to see how classful routing affects the packet forwarding process. Classful routing is enabled using the no ip classless command (classless routing is enabled by default). Classless routing : When a packet’s destination only matches a router’s default route, and does not match any other routes, forward the packet using that default route. Classful routing : When a packet’s destination only matches a router’s default route, and does not match any other routes, only use the default route if this router does not know any routes in the classful network in which the destination IP address resides. ~ CCNA ICND2 Official Cert Guide (3rd Ed) by Wendell Odom I applied this config on my routers. As you can see I enabled classful routing on R1. I also configured default routes on both routers. R1 hostname R1 ! interface FastEthernet0/0  ip address 10.10.10.1 255.255.255.0 ! interface Serial0/0  ip address 192.168.1.1 255.255.255.0 ...

In one lab I did in Packet Tracer, I used EIGRP with Frame Relay in a hub and spoke topology. I did not have a problem with this topology except with the issue of split horizon which can be solved by disabling the feature or implementing static routing (more complex solutions are to change the topology to full mesh or use subinterfaces).  This is the topology of the network: The network is working as it should so I thought of migrating it to OSPF. I haven’t encountered this kind of setup in the CCNA Certification Library and was not really discussed in those books. This is the first time I will be using OSPF in this kind of topology so I don’t really know the nature of this network. I usually use OSPF using point-to-point serial connection with HDLC or PPP. So to do that, I disabled EIGRP and applied the basic OSPF configuration which usually accomplishes the objective of having the routers learn the routes in the network: R1 hostname R1 ! interface Loopback0  ip address 172.1...