Lan design

Unanswered Question
Feb 14th, 2009

We are going to Connect a branch office with our head office.At present our main office has flat network with IP new branch is within 100 mtrs.I am planning to connect the branch with optical fibre .For my branch I have choose Cisco 2960-24TC-L and for main office Cisco 3560-8PC or 3560-12PC for inter Vlan routing.My branch will have the IP address of questions are..1)Will that be a good solution

2)If in branch we will connect some Unmanaged Dlink or low end switch with the Cisco switch for future user expansiopn, will there be a problem.Please Advice and please sugest me some plan if this is not ok.Our organization is not a big one so justification of return of invest is a factor.

I have this problem too.
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Richard Burts Sat, 02/14/2009 - 11:57


The 3560 should be adequate to provide intervlan routing for the branch and the head office. Your post does not tell us whether the head office has any outside connectivity and this might have some impact on the network design (especially in terms of where default gateways might point and whether some dynamic routing protocol was needed.

But based on the description in this post I believe that a /24 for the head office and another /24 for the branch office, and intervlan routing should be an adequate design.

As far as unmanaged devices are concerned there is always a tradeoff about using unmanaged switches. They are less expensive which makes them attractive in some respects. The fact that you can not configure VLANs on them is not a disadvantage in situations where the traffic is all in one VLAN, such as you describe for the branch office. They generally do layer 2 forwarding pretty well. But they do not provide any ability to do troubleshooting. I had an experience at a customer site where they had a networking problem. Their network had only 1 managed switch and a number of unmanaged switches (most of them daisy chained together). We could tell that something was generating large volumes of invalid traffic. But we had no way to find where it was coming from except to go port by port on the unmanaged switches disconnecting and reconnecting ports until we found the one where the invalid traffic stopped. Following this episode they decided to replace most of their unmanaged switches with managed switches to provide better troubleshooting capabilities. From their perspective the money that they saved by purchasing unmanaged switches became less attractive when compared to the cost of the outage that they endured and the extended nature of the outage because they did not have good ability to troubleshoot it. How does you management think about issues such as this?



Leo Laohoo Sun, 02/15/2009 - 20:24

I agree with the above post. Putting an un-managed switch is courting trouble. Whenever I see an un-managed switch when I do a floor walk, I would discreetly remove the infernal machine.

What are your company's future plans regarding growth of the new site? Will you need a PoE switch? Will there be more than 24 ports requirement in the future?

Will you be planning to put any redundant paths to your single Fiber Optic Cable?

soumik1979 Sun, 02/15/2009 - 20:45

Dear All

thank you for your responces...At present at main office we are having only an leased line internet with 1841 router and ASA 5510.The Soon we will going to connect two branch .One branch is the short range branch that I have discribed earlier post.For Another branch will be connect to leased line with 1841 router .I shall use eigrp routing protocol here.

So--The main branch IP is

Short Range branch:

P2p leased line branch:

For Leolaohoo-I am planning for redundant fibre connectivity via two different path.Please advice me over this.If you need more details please reply me via post...

Leo Laohoo Sun, 02/15/2009 - 21:03

Darn. I forgot to ask. Will future growth also include Wireless and VoIP? If you or management is unsure, better get PoE switch just to be ready.

How may we assist you over the redundant fibre?

soumik1979 Sun, 02/15/2009 - 21:17

Right now we dont have any plan for wireless or voip....I have told about the fibre becoz you want to know that ..


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