VLANS - improving network performance

[bladedanny]

Hi All,

 

I know there's been a lot of posts about VLANS but can't see one similar to my question.

 

I'm pretty new to VLANS but think I understand the basics. Basically we have two buildings, the one with the servers and router in works at an acceptable speed, the other can be a bit slow. My main concern is that our admin office is in the second building and access to the network and SIMS can be at times a bit slow.

 

Currently everything from building 1 to building 2 goes via a single copper cat 5e cable supposedly running at a gig. We do have a second cat 5e cable that follows the same route that is not in use.

 

If I have this second cable and the admin office on a separate VLAN to the rest of the building and set the servers and printers to trunk ports for both VLANS would this work?

 

In other words can I send the admin office traffic down one cable to the main switch and the rest of the building down another and see improvements on speed?

 

I know in an ideal world we would link the buildings via fiber but, at least for now, this isn't an option.

 

Thanks,

[foofighterjim]

If you have one link for each, one may be idle whilst the other is at full bandwidth. So I wouldn't restrict yourself on the links between the buildings. I would trunk your two 1GB links to give yourself the maximum throughput possible at all times.

[Sagima]

I think that's a lot of work for not a lot of gain. I think VLANing is a good thing but wouldn't your goal be achieved just by LAGging the two cable together on the switch? It's all of 2 minutes work and if it solves your problem you've saved your self a lot of time

[bladedanny]

If you have one link for each, one may be idle whilst the other is at full bandwidth. So I wouldn't restrict yourself on the links between the buildings. I would trunk your two 1GB links to give yourself the maximum throughput possible at all times.

 

Networking noob time. Can you connect two switches with two cables? I'm sure I've had them both connected and the switches just freaked out, like a network storm.

[Davit2005]

Networking noob time. Can you connect two switches with two cables? I'm sure I've had them both connected and the switches just freaked out, like a network storm.

 

Yep, Spanning tree would block one link if it was enabled but as others have said you could use LACP, just remember set up the ports as LACP before you connect them both up :-)

[Sagima]

It's called link aggregation - it doesn't give you a 2gig link but lets you have two 1gig paths your switch will load balance for traffic. You need to set it up on the switch otherwise it will cause a network loop/storm.

 

How it's done depends on the switch

[bladedanny]

Looks like LAG is what's going to be best. We have netgear switches which look easy enough to configure LAG. I'm presuming it needs to be configured at both ends.

[Sagima]

Looks like LAG is what's going to be best. We have netgear switches which look easy enough to configure LAG. I'm presuming it needs to be configured at both ends.

 

yes it does

[m25man]

TIP:

 

With all switches (especially Netgear) MAKE SURE that the switch config is backed up before you start!

If the switches at each end are the same model its worth making sure they are running the same firmware levels and update both if required.

If they are not the same model at least make sure each switch has the latest firmware on each.

Finally, Make sure that once the LACP trunks are correctly configured, set and working - SAVE the current running config and validate it.

 

Reason for this is there are some buggy versions of Netgear firmware that despite you hitting the "Save" option it doesn't!

The CLI works but the GUI may not. (and Vice Versa).

So the next time the switch gets rebooted (and some models again with buggy firmware do this all by themselves) your newly defined LACP Trunk/LAG/VLAN tags all disappear and you are consumed in a tsunami of hurt!

Netgear seem to have a knack for releasing a Firmware version to fix one thing and break others (which is why they are cheap and obviously don't test their own FW thoroughly).

[teejay]

One other thing is to check you have manually set a root bridge in your spanning tree protocol, if left on automatic it will set the root bridge onto the switch with the lowest MAC address, which is usually some carp old switch that needs binning and will really slow things down.