Solved

vlan and layer 3

Posted on 2013-01-22
3
277 Views
Last Modified: 2013-02-06
I saw 2 configurations that give the same result. I just want your inputs on which one is the best practice.

Scenario 1:
- A Cisco 2921 router (Fa0/1) connects to a 3750 switch (Fa0/2).
- Fa0/1 is configured with 10.10.10.1/24
- Fa0/2 is configured as an access port on vlan 1
- On the switch, vlan 1 is configured with ip address 10.10.10.2/24
- On the switch, default gateway pointed to 10.10.10.1

Scenario 2:
- A Cisco 2921 router (Fa0/1) connects to a 3750 switch (Fa0/2).
- internal subnet is 10.10.10.0/24
- Fa0/1 is configured with 10.10.20.1/30
- Fa0/2 is configured with 10.10.20.2/30
- On the switch, default gateway pointed to 10.10.10.1
- on the router, next hop for 10.10.10.0/24 is 10.10.20.2

Thanks
0
Comment
Question by:biggynet
3 Comments
 
LVL 10

Accepted Solution

by:
ddiazp earned 167 total points
ID: 38808324
Scenario 1 is what you want. Maybe it's just my preference but working with vlan interfaces is much more flexible, easier and more widely accepted.
0
 
LVL 20

Assisted Solution

by:rauenpc
rauenpc earned 167 total points
ID: 38808512
If I'm reading that right, the difference between the two is a routed subnet between the switch and router, versus the Router being on the same subnet.

If you only have the single subnet and never go beyond it, then it's a wash because everything talks directly on the same layer two network.

If you end up with more internal subnets, then there can be a difference. With a single subnet, the default gateway for all devices will be the router. The ip on the switch really only provides management. When you have multiple subnets, all devices need to use the switch as a default gateway to get the best performance (the switch will use the router as a default gateway). This way all internal traffic is L3 switched which is much better than making a single FA link on the router do all the internal routing. An odd situation can happen when you have multiple subnets, and the router exists on one of the subnets that other devices, aside from the switch, reside. If any of those devices were to use the router as a default gateway while other devices were using the switch, you end up with split routing and users will not get consistent performance. Using the separately routed interface/vlan ensures that split routing can't happen.

In the end, I try to use the separately routed interface/vlan whenever possible even if only one vlan exists. It requires a relatively small amount of effort, and it lays the ground work for when additional vlans are needed.
0
 
LVL 9

Assisted Solution

by:Sandeep Gupta
Sandeep Gupta earned 166 total points
ID: 38809672
second scenario is straight forwad ..you connect two boxes directly and give the IP on interface.

In first scenario..both the interfaces are directly conncted and it is a property of vlan you applied ..vlan can be used as L2 as well as L3. here you uses vlan as L3 by giving it ip.

you applied vlan 1 as access so that port and link property do not change..

if you apply vlan 1 on port as trunk ..it will not work.
0

Featured Post

How to improve team productivity

Quip adds documents, spreadsheets, and tasklists to your Slack experience
- Elevate ideas to Quip docs
- Share Quip docs in Slack
- Get notified of changes to your docs
- Available on iOS/Android/Desktop/Web
- Online/Offline

Join & Write a Comment

Suggested Solutions

In the world of WAN, QoS is a pretty important topic for most, if not all, networks. Some WAN technologies have QoS mechanisms built in, but others, such as some L2 WAN's, don't have QoS control in the provider cloud.
Let’s list some of the technologies that enable smooth teleworking. 
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
In this tutorial you'll learn about bandwidth monitoring with flows and packet sniffing with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're interested in additional methods for monitoring bandwidt…

762 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

20 Experts available now in Live!

Get 1:1 Help Now