Thanks for a wonderful 2013, have a safe Christmas and New year everyone.
Merry Christmas
December 25, 2013
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Take a break, Uncategorized | Tagged: 25th. december, Christmas, christmas day, holidays, new year, nye, safe christmas, xmas, xmas day | 
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Posted by Josh Gahan
STP Overview Video
December 12, 2013Below is a short overview of STP and how to navigate it in the CISCO IOS enjoy.
[youtube=http://www.youtube.com/watch?v=zapAZRP7mEk&w=560&h=315]
Leave a Comment » | IOS Commands, Networking, Protocols, Switches, Videos | Tagged: 802.1w, blocking port, ccent, ccent exam, ccent study, ccna, cisco icnd2, cisco packet tracer, designated port, fast ethernet, GNS3, icnd1 study, icnd2, icnd2 exam, interface cost, Microsegmentation, packet racer, root bridge, stp, stp overview, stp port roles, testking | Permalink
Posted by Josh Gahan
Open Shortest Path First (OSPF)
December 12, 2013Moving forwards the next bunch of topics on the list look like so:
Configure and Verify OSPF
- Neighbour Adjacencies
- OSPF States
- Discuss Multi-area
- Configure OSPFv2 and v3
- Router ID
- LSA Types
So lets first get a little background on OSPF before moving any further.
OSPF or Open Shortest Path First is, as the name suggest, an open standard link state routing protocol. The AD of OSPF is 110 and OSPF uses a metric of the outgoing interface Cost to determine the best route. It’s a fast converging and flexible routing protocol which also enables us to separate the topology into areas.
The Topology data for the OSPF network is contained within Link State Advertisements and all routers in the same area share the exact same topology information.
I won’t delve any further into OSPF at this point, i just simply want to introduce the upcoming topics and as you can see there are a few things to get through. So in the upcoming days i will describe the purpose of the LSA’s the RID , configuration and some helpful troubleshooting commands.
Don’t stress too hard this stuff is pretty easy.
Leave a Comment » | ICND2 Topics, Networking, Protocols, Routers | Tagged: ccent, ccna, cisco, Cisco routing, GNS3, icnd1, icnd2, Link State Advertisement, Link State Advertisements, LSA, LSA1, LSA2, LSA3, LSA4, Open Standards, ospf, OSPF network, OSPFv2, OSPFv3, RID, Router ID, routing protocols, test king | Permalink
Posted by Josh Gahan
Routing Metrics
December 10, 2013On our journey through the Cisco ICND2 objectives, we are expected to know a thing or two about “Metrics”
So what is a metric you ask ?
Well a routing metric is used by all routing protocols to decide on the best path to any given network. Not to be confused with Administrative Distance (AD). Which tell the router which path to believe when a router learns a route from more then one routing protocol.
Below is an example of what a metric is, with the use of RIPv2. As you can see R1 has two paths to reach R2. One is out FA0/1 directly to R2 (Which in the real world would be a connected route with a lower AD then RIP) and out FA0/2 through R3.
The metric with RIP is calculated using hop count, so the path with the least hops is the best path. The path highlighted in red would be used in this example.
Leave a Comment » | ICND2 Topics, Networking, Protocols, Routers | Tagged: AD, administrative distance, ccent, ccna exam, cisco ccna, cisco exam, cisco icnd1, cisco icnd2, eigrp, GNS3, hop count, icnd1, icnd2, igp, ripng, ripv2, routing, routing path, routing protocol, test king | Permalink
Posted by Josh Gahan
Split Horizon
December 9, 2013The next routing protocol feature to talk about is Split Horizon.
A feature of Distance Vector that prevents routing loops from forming. Split horizon rules stop a router from sending routing updates back out the interface from which it learnt them from.
Split horizon is used with RIPv2 and EIGRP and yup you guessed it they are Distance Vector routing protocols.
The example below gives you some understanding of what Split Horizon is actually doing. The RIP update going out R1’s FA0/1 interface only includes the subnet 192.168.0.0/24 (Route highlighted in red). As you can see from the routing table below, R1 learnt this network from an update off FA0/3, so Split Horizon Rules allow this network to be sent in an update out FA0/1.
The routes highlighted in black, are learnt from FA0/1 so Split horizon rules will not allow these routes to be sent in an update, over FA0/1
Leave a Comment » | ICND2 Topics, Networking, Protocols, Routers | Tagged: ccent, ccna, eigrp, fa0/1, GNS3, horizon, icnd2, poison reverse, ripv, routers, routing protocol, split, split horizon, test king | Permalink
Posted by Josh Gahan
Default Administrative Distances
December 1, 2013The ICND2 exam asks for knowledge about Routing protocols and their Default Administrative distances. The following table below should be burned into your brain before taking the exam i would imagine.
An Administrative Distance is used so a router can make a decision on how believable the route is as reported by the corresponding routing protocols. Learn this and in the coming days we will use this to configure and Verify both flavours of OSPF and EIGRP.
| Route | Administrative Distance |
| Connected | 0 |
| Static | 1 |
| BGP (External Routes) | 20 |
| EIGRP (Internal Routes) | 90 |
| IGRP | 100 |
| OSPF | 110 |
| IS-IS | 115 |
| RIP | 120 |
| EIGRP (External Routes) | 170 |
| BGP (Internal Routes) | 200 |
| Unusable | 255 |
Leave a Comment » | ICND2 Topics, Networking, Protocols, Routers | Tagged: AD, bgp, ccna, cisco, deafult administrative distance, eigrp, eigrpv6, icnd2, opsfv3, ospf, RIP, routing, routing protocols, static routes | Permalink
Posted by Josh Gahan