On Sat, 2 Dec 2006, Marlon K. Schafer wrote:

Yeah, the waters in the routed vs. bridged argument are getting more and more muddied all of the time.

How many wasted ip's are there in a routed network?  Lots.

This is a big misconception. I don't have time to go into it here, but the truth of the matter is that what you are calling "wasted" is better described as a "cost" in exchange for a benefit.

What are the benefits of a routed network? More control and better customer isolation.

This is only one of the benefits. Scalability especially in a wireless network is a benefit. Alvarion offering VLAN will provide some of the scalability and other benefits that routing will offer. If you think that VLANs are a "scalable" solution, look over the networks owned by the tier 1 providers and see what they are using...routed with BGP.

With the new ap's that block client to client isolation, with vlan switches, bandwidth controlling cpe (or other solutions) and features like what Patrick is talking about routing is becoming less and less critical every day.

No...it's becoming less and less used toward the customer because more and more people are getting into the business of providing internet service without understanding HOW or WHY their network would function better if it were not bridged. You can argue that point if you want, but I have moved more networks from bridged to routed with positive results than the other way around. (there is one notable exception, but I think those results are a bit skewed for other reasons.)

Is bridging "easier"? Yes. Is it common? Among smaller providers, yes. Is is scalable? Only if you use some other technology (such as vlan) to create the separation between the endpoints. As I said, even with VLANs, there is a limit to the scale the network can reach without some routing.

solution. They vlan customers into a single port to the isp. Basically frame a fancy switch, almost frame relay. No routing used at all. We don't even have a good option for routing at the

You don't think their networks are routed? Look at your border router...the public interface is going to have a /30 address...your range of public IP space is routed via that /30 address. You are incorrect in your assumption that there is "no routing used at all".

customer other than doing it just because. It's certainly not a requirement.

No...not a requirement.  It's just a more scalable solution.

Maybe if you are a HUGE isp but certainly not for a few hundreds subs. Hundreds of subs it's still a maybe. And with thousands

I'd disagree here, too. But, I've only been an ISP since 1993, so what do I know...

The technology included in the VL line makes it easier to build a network that can be run by less technical staff. There is a cost savings there too.

It is true that the VL line of products offer some real options. VLANs are a GOOD tool, and having this option DOES offer some cool upsale possibilities. But, VLANs are not intended to be a replacement for a routed network. I've been in this business for a long time. I've built several networks to fairly large scale, including more than one to over 1000 customer base. One that I am now managing has over 3000 subs. That network is using VLANs to provide some services. It is using other technologies as well, but the network is routed. You can't scale a bridged network. It's just that simple. As I said in another post..."you don't have to believe that, others don't have to do it, but it IS the best practice".

Butch Evans
Network Engineering and Security Consulting
Mikrotik Certified Consultant
WISPA Wireless List: wireless@wispa.org


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