Network design and IP addressing

[tnayak]

Hi, I'm a newbie and have been stuck trying to find answers to a few basic questions for several weeks.  I'm not sure why I have not been able to find this information on the web - probably using the wrong search terms.  Per the attached diagram, the network consists of a router, 2 switches, an access point and multiple VLANs, but we may need to add a router in each location as we grow. My questions are:

1) Should I assign a static IP address to the ports that connect the router (g0/1 & g0/2) and switches (GigabitEthernet1/0/52) and access point (BVI1)?  If so, should I assign all of the ports to the same subnet, i.e. each of these ports has an address in the subnet 172.16.1.x?

1a) If router port g0/1 IP address is 172.16.1.1, should I use that as the address for the ip default gateway on switch1?

1b) Does the subnet automatically become the management vlan?

2) What is a good practice to use for assigning IP addresses to the VLAN sub-interfaces on the router? SO far, I have to assign ip addresses to both router ports to the radio sub-interfaces for each vlan on the access point.   I would appreciate any suggestions on how to manage this as the network grows?

ROUTER PORT G0/1 (connects to switch1)                   ROUTER PORT g0/2 (connects to switch2)     

GigabitEthernet0/1.10 IP address = 10.10.10.1            GigabitEthernet0/2.10 IP address = 10.10.10.2 

GigabitEthernet0/1.20 IP address = 10.20.20.1            GigabitEthernet0/2.10 IP address = 10.20.20.2

GigabitEthernet0/1.30 IP address = 10.30.30.1            GigabitEthernet0/2.10 IP address = 10.30.30.2

GigabitEthernet0/1.40 IP address = 10.40.40.1            GigabitEthernet0/2.10 IP address = 10.40.40.2

GigabitEthernet0/1.50 IP address = 10.50.50.1            GigabitEthernet0/2.10 IP address = 10.50.50.2

3)  I want to change the native VLAN and configured the trunk ports on both switches with the command switchport trunk native vlan 666. I also created a sub-interface for the (new) native vlan on each radio on the access point and configured it using the command and encapsulation dot1q 777 native.  I assume that I need to create a sub-interface for this VLAN on both internal-facing router ports. Do I need to assign an IP address to this sub-interface?

4) If some of the people/devices at Site A, i.e. connected to VLAN20 and switch1, move to Site B, i.e. connected to switch2, what is the best way to support their access to VLAN20.  

     Option 1: Add VLAN20 to switch2 - I assume that I would need to add the VLAN and create an SVI.  Does the SVI on both switches need an IP address?

     Option 2: Create a new VLAN and enable inter-VLAN routing between them

5) I currently have DHCP servers on each switch providing ip addresses for the VLANs, should I move to a single DHCP server on the router for all VLANs?

6) Should I use the IP address of the router sub-interface as the DHCP dns-server and DHCP default router?

I would greatly appreciate any suggestions.

[luis_cordova · Accepted solution]

Hi @tnayak,

You have a lot of questions, hehe

1) Should I assign a static IP address to the ports that connect the router (g0/1 & g0/2) and switches (GigabitEthernet1/0/52) and access point (BVI1)?

A: The attached picture shows switch L3, so I recommend configuring SVIs for the routing of the vlan connected to them.

If so, should I assign all of the ports to the same subnet, i.e. each of these ports has an address in the subnet 172.16.1.x?

A: A router can not have the same network configured on two or more of his interfaces.

1a) If router port g0/1 IP address is 172.16.1.1, should I use that as the address for the ip default gateway on switch1?

1b) Does the subnet automatically become the management vlan?

A: If your switches are L3, you should not need a default-gateway.
I suggest you configure a SVI vl100 and a subinterface (G1 / 1.100) in the router to communicate, through a routing protocol, the devices.

2) Do I need to create a sub-interface for each vlan on each router port that connects to a switch?

A: It would not be necessary, since the gateways of the vlan would be hosted in the SVI of your L3 switch.

3) What is a good practice to use for assigning these IP addresses.

A: The idea when assigning IPs is to have clarity about the current use and the growth of your network.
Having that, you can divide your network into subnets, according to the host requirement for each one.

4) Do I need to declare the new native vlan on the router?  How do I do this?

A: The purpose of the native vlan is to give a number of vlan to the packets that arrive at the switch without vlan number.
Because of this, in the link that connects the switch with the router, it is not necessary to assign a native vlan, since no vlan numbers will arrive from the router.

5) I understand that I need to create an SVI on each switch for each VLAN.  Do I need to assign an IP address to the SVI on both switches?

A: Yes, the SVI will serve as a gateway for the vlan that are connected to the switches.
You must keep in mind that networks must be different in each switch, even if they have networks with the same number of vlan.

6) I currently have DHCP servers on each switch providing ip addresses for the VLANs, should I move to a single DHCP server on the router for all VLANs?

A: Managing DHCP requests requires CPU usage, so I do not suggest moving the DHCP pool to the router.

7) Should I use the IP address of the router sub-interface as the DHCP dns-server and DHCP default router?

A: The dns-server command must point to the IP of your DNS server.
If you do not have a local one, I suggest pointing to google.
The default-router command should indicate the IP of your network's gateway, which will be the one you configure in the SVI of your switches.

Regards

[tnayak]

Hi Luis,

Thank you for the information.  Sorry for the number of questions - I feel like I have been pushing on a rope as try to reconcile what I am learning with what I thought I knew:).  Could I impose on you with two follow-up questions?  I found the article (link below) after I posted my question and it discusses creating a sub-interface with an IP address for each VLAN on each router port.  Please confirm my understanding of your answers in regards to this article:

1) Creating sub-interfaces on the router would only be necessary if I want to enable inter-VLAN routing.

2) I still would not need to create a sub-interface for the native vlan on the router ports because the switch would not forward those packets. 

https://www.routerfreak.com/router-on-a-stick-introduction-configuration/

Thanks

Tim

[tnayak]

Hi Luis,

Thank you for the information.  Sorry for the number of questions - I feel like I have been pushing on a rope as try to reconcile what I am learning with what I thought I knew:).  Could I impose on you with two follow-up questions?  I found the article (link below) after I posted my question and it discusses creating a sub-interface with an IP address for each VLAN on each router port.  Please confirm my understanding of your answers in regards to this article:

1) Creating sub-interfaces on the router would only be necessary if I want to enable inter-VLAN routing.

2) I still would not need to create a sub-interface for the native vlan on the router ports because the switch would not forward those packets. 

www.routerfreak.com/router-on-a-stick-introduction-configuration

Thanks

Tim

[luis_cordova · Accepted solution]

hi @tnayak,

1) Creating sub-interfaces on the router would only be necessary if I want to enable inter-VLAN routing.

A: Yesit is.
There are other topologies in which subinterfaces are created, but, I do not want to worry you anymore.

2) I still would not need to create a sub-interface for the native vlan on the router ports because the switch would not forward those packets. 

A: It is not necessary to create a subinterface on the router by the native vlan because the router will not send packets without vlan numbers to the switch.
Now, you could create a subinterface so that the switch, as a device, has a gateway.

On this, for the administration of the switch you could configure the SVI vl100, assign IP address and mask.
Then, create subinterface G1/1.100 on the router.
Then, configure some routing protocol so that these two devices share the conected networks.

Regards