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Beginner

Understanding how to replace layer 2 switch to layer 3 switch

Hi all,

I've major problems to understand how to replace L2 switch to L3 switch.

Router what I'm using is Cisco 2801, and switch is Dell PowerConnect 6224P.

I'm not sure if this is correct place to ask help, because of Dells switch,

but i guess configuration principals should be the same.

I've tried to follow Ciscos configuration examples, but unfortunately I haven't had

any working environment at all yet.

I've possibility to start from scratches, so if assuming I have completely reseted router

and switch, without any configurations, what should I consider?

Assuming:

Router BVI0 is connected to ISP (it will receive ip from ISP's DHCP).

Router port Fe0/0 is connected to switch port G12.

Switch ports G01 - G06 is connected to ESXI4 server.

Switch ports G07 - G08 is Connected to Cisco Access points.

Switch ports G09 - G11 is connected to Workstations (Production 1 and 2)

Switch ports G12 - G17 is connected to Workstations (Production 1)

Switch ports G18 - G24 is Connected to Workstations (Production 2)

VLAN   1 IP addresses 10.10.1.x      (Native) Does it need any ip addresses at all?

VLAN  10 IP addresses 10.10.10.x    (Management)

VLAN  99 IP addresses 10.10.99.x    (DMZ/Guest)

VLAN 100 IP addresses 10.10.100.x (Production 1)

VLAN 200 IP addresses 10.10.200.X (Production 2)

I would appreciate to understand basic configurations correct first,

before getting in to details of AP and ESXI configurations.

All routing between VLANs should be done in Switch.

Should I create VLANs sub-interfaces under router Fe0/0?

Should I assign trunk between router and switch?

Should I assign "base equipments" (router, switch, APs etc.) IP addresses in native 10.10.1.x or

Management 10.10.10.x networks?

Please let me know if you will need any further information.

Thanks in advance!

Regards

Petteri

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3 REPLIES 3
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Hall of Fame Guru

Re: Understanding how to replace layer 2 switch to layer 3 switc

Should I create VLANs sub-interfaces under router Fe0/0?

Should I assign trunk between router and switch?

Should I assign "base equipments" (router, switch, APs etc.) IP addresses in native 10.10.1.x or

Management 10.10.10.x networks?

Not familiar with Dell but in answer to your questions above -

No, you should not need subinterfaces on the router if the switch is L3. You only need to use subinterface with a trunk to the switch if the switch is L2 and you need to route the vlans off the router.

No you shouldn't use a trunk. What you would do is make the port on the L3 switch a routed port and then connect to router using a /30 subnet. Then either run OSPF between router and switch or use static routes ie. on switch -

ip route 0.0.0.0 0.0.0.0    <-- note this is Cisco syntax not Dell

on the router you would need to add a route for each vlan on the Dell switch eg.

ip route 10.10.100.0 255.255.255.0

You should have a separate management network vlan for your switch/router/APs

Don't use vlan 1 for anything and there is no need to worry about the native vlan as you are not using a trunk to connect to the router.

Jon

Highlighted
Beginner

Re: Understanding how to replace layer 2 switch to layer 3 switc

Hi Jon,

Thanks for your suggestions!

I've tried to follow your suggestions, but have met this following problem:

I've assigned IP address 10.10.10.1/24 for Cisco ISR2801 router, and removed all sub-interfaces.

I've assigned IP address 10.10.10.2/30 to the Dell 6224 switch.

I've created VLANs 10,99,100,200 to the switch.

When I tried to assign IP address 10.10.10.3/24 to the VLAN 10, I will receive following error message:

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

console(config-if-vlan20)#ip address 10.10.20.3 255.255.255.0

Subnet conflict between specified IP Address and current configuration.

All routing interfaces, service ports and network ports must be configured on

different subnets.

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

I assume it's Dell related issue, but I hope it's OK to bring it up here.

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

I've looked from the net and found this 6224 configuration script:

ip address 10.10.10.10 255.0.0.0      #####IMPORTANT - THIS CANNOT BE IN ANY OF YOUR DEFINED VLANS/SUBNETS

ip default-gateway 10.10.10.1   #####MUST MAKE SENSE TO THE ABOVE ADDRESS (ie, in same subnet)

ip domain-name subdomain.domain.com   #####YOUR DOMAIN NAME

ip name-server 192.168.1.100   #####NAMESERVER

ip name-server 192.168.1.101   #####NAMESERVER

ip https server   #####ENABLE HTTPS MANAGEMENT

ip routing   #####ENABLE LAYER 3 ROUTING

ip route 0.0.0.0 0.0.0.0 192.168.1.1   #####DEFAULT ROUTE FOR OFFNET ROUTING

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

If I understand this correctly, I should assign un used IP address for the switch, like 192.168.1.1/24 etc?

I would appreciate to hear your suggestion  before I will proceed.

Thanks!

Regards

Petteri

Highlighted
Hall of Fame Guru

Re: Understanding how to replace layer 2 switch to layer 3 switc

Petteri

I've assigned IP address 10.10.10.1/24 for Cisco ISR2801 router, and removed all sub-interfaces.

I've assigned IP address 10.10.10.2/30 to the Dell 6224 switch.

I've created VLANs 10,99,100,200 to the switch.

When I tried to assign IP address 10.10.10.3/24 to the VLAN 10, I will receive following error message:

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

console(config-if-vlan20)#ip address 10.10.20.3 255.255.255.0

Subnet conflict between specified IP Address and current configuration.

All routing interfaces, service ports and network ports must be configured on

different subnets.

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

I assume it's Dell related issue, but I hope it's OK to bring it up here.

No it's not Dell related, it is a general issue. You cannot use the same IP subnet for the P2P link ie. the link between the router and the switch and for a vlan.

What you can do is use 10.10.10.0/24 for vlan 10. Then use an unused subnet for the P2P link eg. 192.168.5.0/30 which goves you 2 useable addresses, so -

switch port -> 192.168.5.1 255.255.255.252

2801 router interface -> 192.168.5.2 255.255.255.252

then on switch -

ip route 0.0.0.0 0.0.0.0  192.168.5.2

on router -

ip route 10.10.10.0 255.255.255.0 192.168.5.1

ip route 10.10.20.0 255.255.255.0 192.168.5.1

etc.. for each vlan

Jon

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