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VLANs / switch/router question

Posted on 2011-05-05
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Last Modified: 2012-05-11
Hi,

I am little confused about the following scenario and I would like for someone to provide some explanation:

Scenario:

-2 Cisco switches: SW1 and SW2
-1 Cisco Catalyst 6500 Series
-SW1 and SW2 are connected via fiber to the 6500
-3 servers : server1 is connected to VLAN20 SW1, server2 is connected to VLAN21 SW2 and server3 is connected to vlan21 on SW1

That being said, if SERVER1 vlan21 SW2 sends traffic to SERVER2 vlan21 SW3, would the traffic be routed to the 6500 and then to go to the switch?

Or basically since SERVER1 and SERVER2 ports are configured on the same VLAN 21 the traffic will go from SW1 to SW2 through the trunk port without going to the 6500 Core Router?


 
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Question by:llarava
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by:peea
ID: 35703238
> if SERVER1 vlan21 SW2 sends traffic to SERVER2 vlan21 SW3, would the traffic be routed to the 6500 and then to go to the switch?

YES, the traffic will go through 6500 if SW2 and SW3 have no direct connection, but it is NOT routing, it is bridging.

> since SERVER1 and SERVER2 ports are configured on the same VLAN 21 the traffic will go from SW1 to SW2 through the trunk port without going to the 6500 Core Router?

if there is a truck link between SW1 and SW2, and VLAN21 is allowed on the trunk connection, no traffic will go via 6500 for same VLAN communication.
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by:llarava
ID: 35703295
Thank you for your answer. I have one more quick question to ask. I think that the switch gets overloaded from the traffic that comes from HUB that is connected to one of the ports.

The HUB has some other devices connected to it and I bealive that they are generating a lot of traffic. I was wondering if you could there is any way to get an idea of the what is happening with the traffic on that particular switch.

We have been having some problems with a switch that is trunking with the switch that holds the HUB and I bealive that this could be the cause but besides the theory about hub and switches I will need to get some prove in order to get replaced the hub.

How could I get some metrics and determine what is going on with the switch?

 
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Author Comment

by:llarava
ID: 35703417
Going back to the original question

> if SERVER1 vlan21 SW2 sends traffic to SERVER2 vlan21 SW3, would the traffic be routed to the 6500 and then to go to the switch?

YES, the traffic will go through 6500 if SW2 and SW3 have no direct connection, but it is NOT routing, it is bridging.

------------------------

Bridging will be used if a trunk ports is not configured between the switches and the traffic will go through the 6500 in order to get from one switch to the other. Is that correct? If so, if no trunk is configured but the traffic is between different VLANs would the traffic be directed to the 6500 through bridging?

Finally if a trunk is in place would all the traffic between different VLANs will go trough the 6500?

 
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Marius Gunnerud earned 2000 total points
ID: 35704264
>since SERVER1 and SERVER2 ports are configured on the same VLAN 21 the traffic will go from SW1 to SW2 through the trunk port without going to the 6500 Core Router?

If the connection to the 6500 still remains and a link is added between SW1 and SW2 Spanning Tree will be in effect. The route traffic will choose will depend on where the root bridge is located. you can force the 6500 to be the root bridge by lowering its priority, then all traffic will be sent via the 6500.

>Bridging will be used if a trunk ports is not configured between the switches and the traffic will go through the 6500 in order to get from one switch to the other. Is that correct? If so, if no trunk is configured but the traffic is between different VLANs would the traffic be directed to the 6500 through bridging?

In this case the 6500 would need to be configured to route traffic between the two vlans and you must point the switches to the 6500 as the default gateway. This would not be bridging.
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by:Don Johnston
ID: 35706308
I'm a bit confused.

>-3 servers : server1 is connected to VLAN20 SW1, server2 is connected to VLAN21 SW2 and server3 is connected to vlan21 on SW1

Which I interpret to mean:

Server 1 - VLAN 20 - SW1
Server 2 - VLAN 21 - SW2
Server 3 - VLAN 21 - SW1

>That being said, if SERVER1 vlan21 SW2 sends traffic to SERVER2 vlan21 SW3, would the traffic be routed to the 6500 and then to go to the switch?

Does this mean Server 1 is on VLAN 21 and connected to SW2?
And Server 2 is on VLAN 21 connected to SW3?

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