vlans and default gateways

[ilpadrino]

I'm trying to determine what kinds of switches to purchase for the datacenter. I plan to have separate vlans for internal departments, servers, branch offices. I have many branch offices connected to 3 routers. Then I have 5 departments totally about 160 ports inside the central location. Then I have 3 groups of servers which I was planning to connect to 3 separate switches. Lastly, I have two internet connections and firewalls.

Do all switches need to be layer 3, or can I have one "backbone" layer 3 switch connected to layer 2 switches? And where do the servers and internal department workstations get their default gateway - the layer 2 switches?

 

[vipergg]

I would say get a backbone layer3 type switch like a 3550 and then you can get layer 2 switches for all the users and servers lie a 2950 or something like that . Default gateway is for being able to be routed between subnets or to the internet so it would be the layer 3 routed interface address on your layer router/switch . Default gateway is coded into the NIC card or if you are running a dhcp server it would automatically be acquired from the server .

 

[ilpadrino]

Ok, so if I had vlan2, vlan3, vlan4 for the 3 sets of servers, these are 3 different subnets. What are their default gateways? Would they be the 2950 switches ip address?

 

[vipergg]

Yes they would be 3 different subnets. Nope the gateway would be the layer3 or router interface address not the switch ip , when you send it to the router it knows how to route it to its destination so you set the pc's nic card default gateway to the router address . Switches do no routing if they are a strict layer 2 switch , but they have blurred the lines as they combined a lot of the switches and routers together so one box can do both switching and routing like a cisco 3550 .

 

[ilpadrino]

Ok, so from what you're saying, would the default gateway for pc's correspond to their vlan subnets? Let's say the servers were 192.168.20.x. Then their default gateway would be 192.168.20.1, which is the assigned address of the 3550's vlan? Even though the 3550 technically has a "real" address in a different subnet?

 

[MTandSAV]

what do you mean with a 'real' address. They 3550 can have dozens of vlans configured with ip address in different subnet.
vlan 2 192.168.20.1/24 server is for example 192.168.20.2/24
vlan 3 192.168.30.1/24 server is for example 192.168.30.2/24
vlan 4 192.168.40.1/24 server is for example 192.168.40.2/24

looking ahead of layer 2 switch:
On a layer2 switch you can have only 1 vlan up up, which should be your management vlan. All other vlans won't show up up, but will work
Obviously you should also create dhcp pools per vlan, so that hosts in such vlan get a ip address in that range.


CCNA, CCNP..partly