Cisco 3550 and VLANS

[MM1]

Hi all,

 

I am looking to make some changes to our network. We currently have a flat network but I am wanting to create separate vlans. However our internet is provided by bgfl so we have a typical Cisco 3550 series switch which then feeds to our own core switch. What is the best option to route between the vlans as obviously I can't touch the Cisco 3550 Switch as it is managed by bgfl.

 

Any help would be appreciated.

 

Thanks

[MM1]

First post was kind of rushed so just to add would my best option here be to just have a L3 Core switch underneath bgfls Cisco 3550 switch and just do my intervlan routing through that? If so what is a good budget L3 switch?

 

Thanks

[ass17]

The answer could depend on how many ports you are going to connect to the layer 3? We have all our buildings on fibre that connect to it. We have two HP 5406zl core switches.

[MM1]

Pretty much same scenario. How do those hp core switches treat you? if anyone has any suggestions of a budget L3 switch?

[ass17]

They are perfect for us, none of the modules have failed.

 

You would have to think Netgear for cheapness and HP/Cisco for best reliability.

[MM1]

Thanks think HP will be a good route.

[MM1]

Looking back at this now I have included a quick diagram of how things kind of look currently. As stated we currently have a layer 2 core switch with a flat network. The plan is to get a new layer 3 core switch and implement a couple of vlans. So if I swap out our current core switch for a layer 3 and setup the vlan interfaces on this so I can do the routing between vlans within our internal network. And then on our core switch set the default gateway to the current default gateway issued by the BGFL, obviously I cannot touch any of the settings on anything above our core switch so this is where I am getting abit lost with ensuring the different vlans can route out to the internet. (I'm presuming this will be fine because I am going to subnet within our given 10. range).

 

 

Any help would be appreciated.

 

Thanks

Edited November 11, 2017 by MM1

[mukz]

We have a firewall vlan on our setup, bgfl use an IP address 10.xx.xx.1 as the gateway. You then set a route to that ip address and any vlans which you have configured will hit the internet.

(Sorry if it doesn’t make sense) typing in a hurry whilst trying to help my Nephew.

 

I can give you an example config when i get back into the office.

[ReBoot]

You just need to set the default gateway on your new L3 core switch to the IP of the BGFl 3550. The link between your core switch and the 3550 will be untagged (no VLANs).

 

You current edge switches will need to be setup with whatever VLANs you are planning and the links between the edge and core will need to be trunked. On the core switch you will need layer 3 interfaces for each VLAN and the IPs of these interfaces will become the default gateways for clients on the VLANs.

 

Note if you were thinking of each edge switch as a single VLAN this would be a waste of time and you should stick with what you have. Likewise if all VLANs are reachable from any client then there is not much point in implementing VLANs - VLANs are typically used to achieve separation between clients or treat traffic differently using different QoS schemes per VLAN. If you have no need of this type of network forget VLANs.

[FN-GM]

Note if you were thinking of each edge switch as a single VLAN this would be a waste of time and you should stick with what you have.

 

I disagree, putting each edge switch on a VLAN has some benefits such as cutting down broadcast traffic.

[ReBoot]

Yes agreed it will reduce the scope of broadcast traffic to each VLAN if that's an issue.

[MM1]

We have a firewall vlan on our setup, bgfl use an IP address 10.xx.xx.1 as the gateway. You then set a route to that ip address and any vlans which you have configured will hit the internet.

(Sorry if it doesn’t make sense) typing in a hurry whilst trying to help my Nephew.

 

I can give you an example config when i get back into the office.

 

Yea that would be great please and thanks for the help

 

You just need to set the default gateway on your new L3 core switch to the IP of the BGFl 3550. The link between your core switch and the 3550 will be untagged (no VLANs).

 

You current edge switches will need to be setup with whatever VLANs you are planning and the links between the edge and core will need to be trunked. On the core switch you will need layer 3 interfaces for each VLAN and the IPs of these interfaces will become the default gateways for clients on the VLANs.

 

Note if you were thinking of each edge switch as a single VLAN this would be a waste of time and you should stick with what you have. Likewise if all VLANs are reachable from any client then there is not much point in implementing VLANs - VLANs are typically used to achieve separation between clients or treat traffic differently using different QoS schemes per VLAN. If you have no need of this type of network forget VLANs.

 

Will everything (all vlans) route ok back and fourth out to the internet from the core switch to the bgfl 3550 despite the port been untagged.

 

The real reason for us looking at implementing vlans was mainly to try and reduce broadcast traffic. Feel free to make suggestions though as It's great to hear people's opinions and recommendations.

 

Thanks for all the info btw

[MM1]

I disagree, putting each edge switch on a VLAN has some benefits such as cutting down broadcast traffic.

 

Yea this is the plan

[pow]

I haven't read the above in great detail, but I always put the 'internet' on it's own VLAN - so only the router and the gateway on that VLAN. The way I've handled this at a school that has a gfl connection to a non school owned switch is to define the internet vlan with a subnet in that range (for example if it's on 10.10.10.1 then I would define the internet vlan as 10.10.10.1/24), tag the switchport that connects to the uplink as that VLAN and then define the default route on the core to the existing IP address of the router.