a VLAN Question ?

CCIE_2011

Hi all .. . I'm quite confused about this ?

If 2 users are belonging to the same VLAN!! How can they communicate if there is a L3 device in between ?

small demonstrations :

PC1

4503 (L2)

6509 (L3)

4503 (L2)

PC2

Also confused about those Qs:
1. How broadcasts produced from PC1 reaches PC2?
2. They should belong to the same IP segment, correct !!
3. Can 6509 become VTP server ?

Thnks in advance

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Comments

APA

Is the router doing inter-vlan routing???

Are they the same vlan using the same gateway? or are they using different gateways but have been given the same vlan id by accident??? (big no no!!!)

CCIE_2011

the 6509 is a L3 device so it should handle interVlan routing.
PC1 & PC2 have the same vlan.

bighornsheep

There are different ways of doing this. But I would set your 6509 as the server running VTP. Set your two 4503 both as client in the same vtp domain as the 6509.

Create your vlan in the 6509 which will then be transferred to the 4503 automatically. (Make sure you configure the link between the 4503s and the 6509 as trunk)

And then you just have to configure the ports PC1 & PC2 are connected to on the 4503 as access ports in the vlan that you created.

CCIE_2011

bighornsheep wrote:

There are different ways of doing this. But I would set your 6509 as the server running VTP. Set your two 4503 both as client in the same vtp domain as the 6509.

Create your vlan in the 6509 which will then be transferred to the 4503 automatically. (Make sure you configure the link between the 4503s and the 6509 as trunk)

And then you just have to configure the ports PC1 & PC2 are connected to on the 4503 as access ports in the vlan that you created.

If i change my network into he following :

PC1 ---- 4503 L2

6509 (L3)

4503 (L2) ---- PC2

>(access)

(distribution)---- (Core)

(distribution) --- (Access)

will it be a good practice to also make 6509 L3 (core) as a VTP server?
it is also possible to add PC1 & PC2 to the same vlan ?

tech-airman

CCIE_2011,

CCIE_2011 wrote:

Hi all .. . I'm quite confused about this ?

If 2 users are belonging to the same VLAN!! How can they communicate if there is a L3 device in between ?

small demonstrations :

PC1
4503 (L2)
6509 (L3)
4503 (L2)
PC2

Also confused about those Qs:
1. How broadcasts produced from PC1 reaches PC2?

The behavior would highly depend on if the port on the 6509 connected to the left 4503 is in "switch port" mode or not. If it's not in "switch port" mode, then it's treated like a router port. Similarly, the behavior would depend on the "switch port" mode of the 6509 that is connected to the right 4503. If it's not in "switch port" mode, then it's treated like a router port. So without further ado, I have to ask:

Is the physical port on the 6509 connected to the left 4503 in "switch port" mode?
Is the physical port on the 6509 connected to the right 4503 in "switch port" mode?

CCIE_2011 wrote:

2. They should belong to the same IP segment, correct !!

Yes, the whole common VLAN should belong to the same IP subnet.

CCIE_2011 wrote:

3. Can 6509 become VTP server ?

Thnks in advance

I don't see why not.

tech-airman

CCIE_2011,

CCIE_2011 wrote:

bighornsheep wrote:

There are different ways of doing this. But I would set your 6509 as the server running VTP. Set your two 4503 both as client in the same vtp domain as the 6509.

Create your vlan in the 6509 which will then be transferred to the 4503 automatically. (Make sure you configure the link between the 4503s and the 6509 as trunk)

And then you just have to configure the ports PC1 & PC2 are connected to on the 4503 as access ports in the vlan that you created.

If i change my network into he following :

PC1 ---- 4503 L2
6509 (L3)
6509 (L3)
6509 (L3)
4503 (L2) ---- PC2
>(access)
(distribution)---- (Core)
(distribution) --- (Access)

From a Core/Distribution/Access perspective, here's how the devices fall:

Core = 6509 Supervisor Engine (L3 routing)
Distribution = 6509 switch fabric between the switch cards (L2 switching)
Access = 4503 Switches (L2 switching)

Good try though.

CCIE_2011 wrote:

will it be a good practice to also make 6509 L3 (core) as a VTP server?

Given the number of devices, sure why not. Make sure you specifically configure the 4503 switches as VTP clients first before connecting the 6509 to the 4503.

CCIE_2011 wrote:

it is also possible to add PC1 & PC2 to the same vlan ?

Assuming you configured the 6509 Layer 3 Switch to be the VTP server and the 4503 Switches to VTP Client mode then you create the VLAN on the 6509 and associate the switch ports on the 4503 connected to the PCs with the same VLAN, sure it's possible.

mikearama

tech-airman wrote:

Assuming you configured the 6509 Layer 3 Switch to be the VTP server and the 4503 Switches to VTP Client mode then you create the VLAN on the 6509 and associate the switch ports on the 4503 connected to the PCs with the same VLAN, sure it's possible.

This is the smart way to config the router/switches, but I have a suggestion... there's no logical reason for the two pc's to be in the same ip subnet. In fact, there's very good reason for them NOT to belong to the same segment.

While your design works fine in a lab environment, where you're studying vlans and vtp... but not playing with a routing protocol, try introducing eigrp or ospf. Ouch. You'd have a router with the same subnet out of two interfaces.

So, I'd suggest:

PC1 (10.10.10.1)

> 4503

6509

4503 <

PC2 (10.10.20.1)

Put both PC's in the same vlan, but assign them static IP's in different subnets. (go with static, cause cisco suggests against having PC's that are in the same vlan from being in different subnets, just cause DHCP has a hard time deciding which subnet to assign IP's from).

Hope that didn't confuse things more,
Mike

hectorjhrdz

This is the smart way to config the router/switches, but I have a suggestion... there's no logical reason for the two pc's to be in the same ip subnet. In fact, there's very good reason for them NOT to belong to the same segment.

While your design works fine in a lab environment, where you're studying vlans and vtp... but not playing with a routing protocol, try introducing eigrp or ospf. Ouch. You'd have a router with the same subnet out of two interfaces.

So, I'd suggest:

PC1 (10.10.10.1)
> 4503
6509
4503 <
PC2 (10.10.20.1)

Put both PC's in the same vlan, but assign them static IP's in different subnets. (go with static, cause cisco suggests against having PC's that are in the same vlan from being in different subnets, just cause DHCP has a hard time deciding which subnet to assign IP's from).

Hope that didn't confuse things more,
Mike

O.O i was wondering that the last week and you iluminate me now.

thnks dude

fid500

An 6509 switch in the distribution layer ? Your company must be richhhhh.

CCIE_2011

fid500 wrote:

An 6509 switch in the distribution layer ? Your company must be richhhhh.

If it is or not .... At the end just a small employee in a support department..... This will not make a difference to me as long as my salary at my account at the end of the month