Same DHCP server serving requests for 2 VLANs

[Damir Reic]

Hi,

I have several Cata 3500XL switches connected to one 1 HP L3 switch which is connected Sonicwall router. Vlan1 has subnet of 10.10.0.0/24 and Microsoft DCHP server lays inside VLAN1.

Now i want to add VLAN11  (192.168.10.0/24) as second data VLAN but DHCP requests should go to microsoft DCHP server.

This is what i did:

Configured VLAN11 IP on each cisco switch

IP default gateway with IP from other subnet (i guess this is bad since maybe it should be IP of VLAN11 on HP L3 switch?)

Trunk ports are configured to pass everything on cisco switches

On VLAN11  i configured IPhelper IP to be MS DHCP server on each Cisco switch

I haven't tested this yet but i have problem in process.I can't ping VLAN11 IPs between switches (i configured VLAN1 and VLAN11 with IP). When client plugs computer to a port that belongs to VLAN11 will i be sure that client will get IP from the 192.168 range or there is possiblity that he gets IP from the management VLAN range?

[acampbell · Accepted solution]

Damir,

3500XL are layer 2 only switches.
Ip config on them is really just to allow you
to manage them.

You are right with some of what you have done.

1) Create VLAN 11 in all switches if your VTP mode is transparent.
Only need to create it on the VTP server switch if you are
using VTP client/server with the same VTP domain.

2) Make sure that VLAN 11 is in the trunks to the layer 3 switch.

3) On the layer 3 switch create an SVI fir Vlan 11.

int vlan 11
ip address 192.168.10.1 255.255.255.0

4) Add an ip helper in this new SVI to point at the DHCP servers address.

5) Create a new scope on the MS DHCP server
Addresses here aree only suggestions
Name = VLAN11
Scope range = 192.168.10.11 - 200 Mask 255.255.255.0
Default gateway 192.168.10.1
Add any DNS servers address domain names etc
Activate scope

6) Make sure that you add a route from the router for
192.168.10.0/24 next hop the L3 switch vlan 1 SVI address

Hope this makes sense to you.

Regards,
Alex.
Please rate useful posts.

[Damir Reic]

Hi,

thanks for answer, i know 3500XL is L2 switch but this is what troubles me:

interface Vlan1

ip address 10.10.0.253 255.255.255.0

interface Vlan11

ip address 192.168.0.253 255.255.255.0

This is configured between two 3500XL switches and i can't ping IPs on VLAN11 between 2 3500XL (trunk port passes all). Can i have 2 VLAN with IP on this switch?

[acampbell]

Damir,

The 3500 switches can only support
1 interface vlan (SVI)

This is because it only has 1 ip route which is
a default route
you configure the route :-

ip default-gateway a.b.c.d

a.b.c.d should be the next hop alond the vlan of the SVI

e.g.

interface vlan 1
ip address 10.10.0.200 255.255.255.0
!
ip default-gateway 10.10.0.254
!

I am also including the link to the config guide
http://www.cisco.com/en/US/docs/switches/lan/catalyst2900xl_3500xl/release12.0_5_wc_1_/swg/sc.html

By the way these switches are really very old now
Cisco will not support them any more
No IOS upgrades etc

Hope this helps

Regards,
Alex.
Please rate useful posts.

[Damir Reic]

Acampbell thanks for clarification!