Sunday, November 1, 2009

IPv6 Static Routing

In this hands-on exercise, we configure IPv6 addresses on 3 routers in a triangle. Then we configure IPv6 static routes to allow the 6 IPv6 subnets (3 loopback, 3 P2P links) to be accessible on all 3 routers.
Static routes are easy to understand. At first glance they appear simple. You just manually configure which next-hop to go to for each subnet destination. But in actual use they are very complex. In our example with 3 routers and 6 subnets, we end up using 12 static route commands to implement our routing. Even then we do not achieve full redundancy, because static routes do not reroute around network failures. Even a small production network with approximately 20 routers would have too many static route commands necessary to make a static-route implementation feasible. In the real world, using dynamic routing protocols to minimize manual configurations (minimizing both effort and errors) is necessary to achieve a robust environment.
That said, static routes are sometimes useful at the edge of your network. You redistribute static routes into your routing protocol at the edge of your network where you don't want to dynamically route with routers outside your administrative control. The goal there is just to use the static route to inject a route into your routing protocol. Not to use the static route as your primary routing mechanism.

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8 Comments:

Blogger chrisv25 said...

Thanks for the new vids! I am taking BSCI on Nov 30 and am currently reviewing OSPF (vid 19 right now) using your lessons. I am still very sketchy on IPv6 so, i will definitly be looking at the new stuff!

November 25, 2009 at 5:48 AM  
Blogger matthew said...

Hey, just wanted to let you know that I really do enjoy the podcasts that you do. Please keep them coming!

December 2, 2009 at 10:15 AM  
Blogger Ulrik Poulsen said...

Hi Darrel

I will soon be studying for a CCNA and have just downloaded your great podcasts. I have a quick question though: I can see that you are using a mac, which I would like to do as well. What app are you using to connect to the routers? I know on a PC you use hyperterminal, but information on how to use a mac is hard to come by. I was hoping you could tell me what your setup is.

Thanks again for some great tutorials.

/ ulrik

March 11, 2010 at 2:15 AM  
Blogger Darrell Root said...

I use ZTerm with a keyspan USB to serial adapter. I believe I discuss that in the first episode (scrounging gear and getting console).

March 20, 2010 at 10:20 PM  
Blogger Justin said...

Why are you configuing the loopback interfaces with an IP? Is this required or just for an example in this lab?

November 24, 2010 at 12:02 PM  
Blogger Darrell Root said...

Loopback addresses are always "up" and are not vulnerable to hardware failures. There are two advantages to using them:

1) If your primary DNS entry for a router is the loopback, you'll be able to ssh to that router even if one of the physical interfaces is down. But if you use a physical interface as the primary DNS entry, if that interface goes down you won't be able to ssh to the box via its DNS entry even if you had another path.

2) The loopback address is used as a stable identifier for some routing protocols (OSPF, EIGRP). Since loopback addresses never go down, that's more stable than using a physical interface.

You are right that reason #2 does not apply for a static route example. But reason #1 still applies. And even if you deploy a production network with static routing (not something I would recommend because it's hard to reroute around failures) you might convert to dynamic routing in the future.

November 26, 2010 at 12:31 PM  
Blogger katty said...

192 168 1 1 is the management panel address for the ADSL modem. Worldwide provider of modem devices uses

September 23, 2016 at 5:21 AM  
Blogger Ajay Kumar said...

192 168 0 1 is a default IP address of many routers as they are already set through their companies, so that is the reason why during configuring these routers you need to be on the same network.

December 27, 2016 at 5:31 AM  

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