08-13-2008 11:58 PM - edited 03-06-2019 12:47 AM
Hi Cisco Gurus,
I have a LAN running in a flat network. The devices are 1 L3 switch and 3 L2 switch and 1 router. Currently no VLAN is configured, and all are running in VLAN 1.
We are planning on LAN expansion and we will be using another subnet. My problem is, what's the best configuration for this requirement? My concerns are as follows:
1. Can I retain the existing configuration, meaning the existing subnet will be in VLAN 1 and the new VLAN on VLAN 2?
2. For interVLAN routing, I plan to do the following configs in my L3 switch:
-ip routing (to enable L3 functionality)
-interface vlan2, with IP address (for SVI on new VLAN)
-configure encapsulation trunk on switch-to-swtich ports
=are these configurations enough?
Thanks in advance for those who will reply!
Emman
08-14-2008 01:35 AM
Hi ,
Yes , you can do same thing..
L3 : 1. create Vlan 2 and assign IP to that Vlan.
Ip routing i.e inter vlan routing should be done on L3 itself.
Configure three ports as trunk ports to connect L2 switches.
If you want to have control over L2 switches , create Vlan 2 on all L2 switches.
assign IP address to all three and configure ip default-gateway as Vlan 2 Ip address of L3 Switch.
Configure one port of L2 as trunk to connect it to L3 switch.
The purpose is you can place servers or PC either in Vlan 2 or in Vlan 1 according to requirement .
Thanks,
Satish
08-14-2008 04:08 PM
hi Satish,
Thanks for your helpful advice! I will try to implement this in our production tonight and keep you updated of the outcome...thanks again!
Brgds,
Emman
08-14-2008 04:14 PM
hi Emman
just for ur information
the config i have posted
fuuly oerational
and if u find if configurable then it will be very useful for u
and good luck
08-14-2008 01:39 AM
hi Emmanuel
just follow the folowing instructions and evry thing will be ok
first i will use an example for u to make easy and u can use in ur network aswel
vlan 2 192.168.2.0 / 24
vlan 3 172.16.1.0 /24
first configure the L2 switches as following
vlan 2
name vlan_2
vlan 3
name vlan_3
the folowing config on the switch i asume u have 2950 which use only encapsulation dot1q
lets say this is the port connect the two swtches L2 and L3
interface fa 0/24
switchport mod trunk
no shut
and the folowing example for two access port connected to the client invlan2 and 3
interface fa 0/1
switchport mode access
switchport access vlan 2
spanning-tree portfast
no shut
interface fa 0/2
switchport mode access
switchport access vlan 3
spanning-tree portfast
no shut
now let move to L3 switch
in this switch i will configure DHCP for u for each vlAN IN ths case u dont need to add ip address to each client connect to the access ports
first lets configure the interface connect to the L2 switch trunk
int fa 0/24
switchport trunk encapsulation dot1q
switchport mode trunk
no shut
creat vlan 2 and 3
vlan 2
name vlan_2
vlan 3
name vlan_3
now lets crea layer three vlan interfaces SVI
interface vlan 2
ip address 192.168.2.1 255.255.255.0
no shut
interface vlan 3
ip address 172.16.1.1 255.255.255.0
no shut
now let enable L3 routing between vlans enter this command
IP routing
now lets configure the DHCP and notice that each vlan will use the corsponding SVI as a default gate way
ip dhcp pool vlan2
network 192.168.2.0 /24
default-router 192.168.2.1
ip dhcp pool vlan3
network 172.16.1.0 /24
default-router 172.16.1.1
ip dhcp excluded-address 192.168.2.1 172.16.1.1
now lets go to the last stage which is th connectivity wiith router
i will use here static route and default route
and the connection between the L3 switch and the router interface will be over layer three witchport
lets say in L3 u gonna use port fastethernet 0/1 to connect to the router do:
int fa0/1
no switchport
ip address 10.1.1.1 255.255.255.0
no shut
now lets make a default route on the L3 switch point to thr router for internet or any thing els
ip route 0.0.0.0 0.0.0.0 10.1.1.2
where 10.1.1.2 is the router ip address directly connect to the L3 port we just configured
no lets move to the router
lets say the router fa0/1 connected to the L3
interface fa0/1
ip address 10.1.1.2 255.255.255.0
no shut
now lets configure a route for our vlans in the router
ip route 192.168.2.0 255.255.255.0 10.1.1.1
ip route 172.16.1.0 255.255.255.0 10.1.1.1
then configure ur router for any thing else
now the network
fully operational and has vlans and VLAN routing and DHCP
important: if u miss any of the above config command u may loss the connectivity
good luck
please, if helpful rate
08-14-2008 07:14 PM
Hi Marwanshawi,
thanks a lot for this configuration, I will compare this to my configuration.
sure no problem, will rate your post afterwards...thanks again!
08-18-2008 09:53 PM
Hi All,
the VLANS are working now.
The existing VLAN before--VLAN 1 can connect now to VLAN 2. After doing all your suggestions, I still cannot ping from VLAN 1 to VLAN 2 because the default-gateways of switches in and hosts in VLAN 1 is pointed to the router's FastEth interface. Since this vLAN is already existing, and it would be impractical to change all hosts' default-gateway setting, I added a default route in the router for the new VLAN:
ip route (VLAN2 subnet) (subnetmask) (L3 switch's FastEth interface)
is this just OK? since after doing this set-up, both VLANS can now communicate bidirectionally.
Thanks for the answers and enlightenment!
Brgds,
Emman
08-18-2008 10:10 PM
although it is not best practice but its good work around and iam happy its work now
good luck
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide