What is ARP and how does it actually work? I’m surprised at the amount of people who don’t know exactly what it does and how important it is.
To illustrate, I’m going to use this extremely simple network:
Both of these systems are really just connected to a home router. Remember that these ports are really just switched ports. The only time they traverse a layer3 port is when they are sending traffic outside the local LAN.
ARP is the Address Resolution Protocol. Essentially all it does is resolve a logical IP address to a physical Hardware (MAC) address.
In the above diagram, if 10.20.30.108 wants to send traffic to 10.20.30.4, it will move down the IOS layers. It will eventually get down to layer2. The layer2 header needs to have both a source and a destination MAC address. 10.20.30.108 has the layer3 address already, but not layer2. This is where ARP comes into the picture.
Sign it here: http://etherealmind.com/petition/
DO IT!!!
We the undersigned ask you to sign our petition.
We are the people who are learning about Data networking and Cisco IOS software. As students and practitioners, we need to learn theory and knowledge and then to take that knowledge and practice on Cisco IOS software.
We want to be able to practice that knowledge, and demonstrate our competence. We know that you are considering the value. This petition is to show our need for this solution. Wendel Odom discusses the possibility Cisco Considers IOS for Certifcation Self Study and we are calling for Cisco to make an option available.
This experience and knowledge we gain gives us the capability to make the most of Cisco equipment for our employers, your customers. We help drive the best return on investment, and keep the network performing in the way that your customers expect.
STP works extremely well, but you lose operational links with it. i.e. you lose bandwidth. There are also quite a few other problems with STP (convergence speed being 1 of them)
TRILL seems to be the new technology coming in to resolve this. I’ve gone through the RFC: http://tools.ietf.org/html/rfc5556 and it looks pretty awesome stuff. I particularly like the following:
3.2. Zero Configuration and Zero Assumption
Both bridges and hubs are zero configuration devices; hubs having no
configuration at all, and bridges being automatically self-
configured. Bridges are further zero-assumption devices, unlike
hubs. Bridges can be interconnected in arbitrary topologies, without
regard for cycles or even self-attachment. Spanning tree protocols
(STPs) remove the impact of cycles automatically, and port
autolearning reduces unnecessary broadcast of unicast traffic.
As promised, I’ll now start writing up solutions to my previously posted labs. I hope this will spur up some conversation. I still stress that you should always try to do the lab without my help first. This will ensure you learn how to do it properly. Also remember that there are always multiple ways to do certain labs, so don’t take my solution as gospel.
I’ll be walking through my first MPLS lab which was originally posted over here: http://mellowd.co.uk/ccie/?p=518
- Use RIP as the routing protocol on CPE devices
- CPE1 and CPE5 belong to Company_A
- CPE2 and CPE6 belong to Company_B
- Each site has a /24 that is advertised via the loopback
- CPE1 should be able to ping CPE5’s loopback and vice-versa
- CPE2 should be able to ping CPE6’s loopback and vice-versa
- Different companies should NOT be able to ping each other. They must stay completely separate
I initially started this blog to post labs I had created for myself during my studies. I’ve noticed that I don’t get a lot of comments on the actual lab posts I make though. I’m hoping to change that, so I’ll be starting to create my own solutions to those labs in order to initiate some discussion.
I’m going to hit them at random though, so be aware :) In future I’ll post a lab, leave it for a week, and then provide my solution to it. That way you get to figure it out for yourself first. If you really are stuck the solution will be up in a week. Remember though that there is always more than 1 way to do a lab, so don’t take my solutions as gospel.
I’ll start one later and will do more whenever I have a bit of free time :)
Now that my CCIP has been completed, I’d like to dive a bit into Juniper. We have a few Junipers in our network and I’d like to learn more about them. The few times I’ve used JunOS already I’ve been impressed.
I might do either the JNCIA-ER or the JNCIS-ER. I’ll see how much time I have.
Juniper do a great job of giving LOTS of free study material on their site, so I suggest you take a look as well.
I’ve gone and configured myself a Juniper Olive (google it) for actual labbing and so on. I might just put up a couple of Juniper labs!
I’ll put up a few things here and there as I go along.
I nailed the MPLS exam this morning so that completes my CCIP!
I’d like to finish the MPLS Fundamentals book I’m reading as there is a lot of stuff in there that’s not in the exam.
After that I’d like to do my JNCIA and then start reading LOTS of books so I can eventually do my CCIE written.
The diagram is the same as my last VPN Lab. Also it uses my MPLs topology found over here: http://mellowd.co.uk/ccie/?p=522
This is the topology for this lab (click for a bigger image):
- Customer1 and Customer 2 both have MPLS vpn’s through the ISP core.
- Customer1 is using OSPF and Customer2 is using EIGRP
- Customers should have no access to each others networks
- Customers should be able to reach all their sites from all their sites
- The ISP wants to monitor the CPE routers via their monitoring server. Create another loopback on each CPE router and give them all a /32 loopback in the 172.16.1.1/24 range – i.e. 172.16.1.1/32 for CPE1, 172.16.1.2/32 for CPE2 and so on
- Ensure the monitoring router can get to all these /32 routes (and ONLY these /32 routes) – It should not know about any customer routes – CPE routers should only see their OWN loopbacks in the routing table
I’ve been real busy at work recently, and so I’ve neglected my site quite a bit. I’ve got a bunch of ideas for more updates and they will be coming soon! :)
I’ve booked my MPLS exam for next month. I really think I should’ve written it earlier, but again with work being full up, it’s not that easy to fit in the study time needed. We’ll see how it goes :)
This lab will test a Central Services MPLS VPN.
The diagram is the same as my last VPN Lab. Also it uses my MPLs topology found over here: http://mellowd.co.uk/ccie/?p=522
This is the topology for this lab (click for a bigger image):
- Customer1 and Customer 2 both have MPLS vpn’s through the ISP core.
- Customer1 is using OSPF and Customer2 is using EIGRP
- Customers should have no access to each others networks
- Customers should be able to reach all their sites from all their sites
- The ISP is now providing a mail relay for it’s customers to use. Ensure that all customers can get to the 10.200.1.1/24 subnet through their vpn’s, but they must still be seperated from each other.
Comments