Solved

Design of VLANs

Posted on 2012-03-12
5
461 Views
Last Modified: 2012-05-15
I am working with a client who has some Cisco equipment.

network design is very simple now ; all machines in one VLAN and one subnet.

they like to go with a VLAN based solution , they have a Cisco switch 3750 (24 port) and a ASA (5510) . They also have six Dlink (layer3) switches.

The Idea is to use Cisco 3750 as a core switch ; subnet network to 5 different IP ranges ( for 5 departments ) and put each department on a separate VLAN.

They also have another location which will be connected to primary site using a site-to-site VPN (through Cisco ASA) .So ASA provides site-to-site connectivity and Internet access.

machines on that site also need to be in a different VLAN but should be able to talk to servers in primary site.


so .. with this scenario in mind ; here are my thoughts :

we need one dedicated switch on each subnet ( probably those Dlinks)
we need to enable trunking on each Dlink switch.
Each Dlink switch  will be connected to core Cisco switch using its trunk interface.
Core switch performs required routing and send traffic to ASA if required.

Is this right ? I am not quiet sure if ASA should be VLAN aware too ... any thoughts ?
0
Comment
Question by:akhalighi
  • 2
  • 2
5 Comments
 
LVL 4

Expert Comment

by:schmitty007
ID: 37710618
In this scenario your 3750 L3 switch can do the routing between Vlans and you would need to trunk the ports between switches. So your ASA would only have to know that the other subnets are reachable through the 3750.

 There is no need to dedicate one switch per VLAN unless you just wanted to, it is possible to simply assign different switchports to access the vlan intended. It would help to understand the physical topology to answer this question. Are the devices in these 5 different areas cabled back to the same data closet or different closets?

 You would have all 5 Vlans on all switches and simply assign a range/specific ports to each VLAN. You could also use VTP to manage Vlans across the switches if you had a native cisco switching environment.

Example
Int fa0/1
switchport access vlan 10

int Fa0/2
switchport access vlan 20

I would shutdown Vlan1 and pick one Vlan to be your management Vlan for your switches.
I would also recommend using RPVST - rapid per vlan spanning tree.
0
 
LVL 10

Author Comment

by:akhalighi
ID: 37711807
Thanks for all information , can we enable rapid spanning tree even in a Dlink-Cisco mix ?
0
 
LVL 4

Expert Comment

by:schmitty007
ID: 37711848
Spanning-tree is IEEE and is not proprietary to cisco so as long as the switch itself supports RPVSPT then absolutely. You said they are L3 switches so I would assume yes but, to confirm just look up the model numbers on the manufactures website it should confirm / deny.
0
 
LVL 29

Accepted Solution

by:
pwindell earned 500 total points
ID: 37748808
The Idea is to use Cisco 3750 as a core switch ; subnet network to 5 different IP ranges ( for 5 departments ) and put each department on a separate VLAN.

That is the wrong reason to want to do that in most cases.
The primary reason would be because you have more than 200 machines on a segment and it is starting to suffer degradation from the level of Broadcasts.

If you have less than 200 machines, and have no special case security needs,...then leave everything in a single segment.

VLANs,...I try pretty hard to not even use the term, the trem often just creates confusion, voodoo, and visions in people's minds that go beyond all it really amounts to in the end.    An L3 Segment is an L3 Segment, how you "get there" is not that relevant.   If it is a conventional LAN Router it is based on the physical interfaces of the device,...if it is an L3 Switch then it is based on how you group the Switch Ports into logical Router Interfaces by using the VLAN config,...but in the end,...either way,....L3 Segments and just L3 Segments.
0
 
LVL 29

Expert Comment

by:pwindell
ID: 37748822
Simple principle to follow:

For every 200 machines,...create a new /24 (254 host) Segment.

Whether that is done with physical interfaces on a convention LAN Router or with virtualized Interfaces on a L3 Switch really doesn't matter.
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

There are times where you would like to have access to information that is only available from a different network. This network could be down the hall, or across country. If each of the network sites have access to the internet, you can create a ne…
Microservice architecture adoption brings many advantages, but can add intricacy. Selecting the right orchestration tool is most important for business specific needs.
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
Both in life and business – not all partnerships are created equal. Spend 30 short minutes with us to learn:   • Key questions to ask when considering a partnership to accelerate your business into the cloud • Pitfalls and mistakes other partners…

910 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

19 Experts available now in Live!

Get 1:1 Help Now