DHCP ON CORE SWITCHES

[ajay chauhan]

Hi,

Can we enabled DHCP on both core switches ? how would redundancy will take place please explain if its possible.

Thanks

Ajay

[andrew.prince · Accepted solution]

Ajay,

1) Can we enabled DHCP on both core switches - yes you can if you really want to.

2) how would redundancy will take place - it would not

You would have overlapping DHCP scopes - the issue is the time it takes for the DHCP assignment to take place, as you are aware before an IP is issued, the DHCP server will send out a request to see if the IP is already taken.  As you cannot sync DHCP address assignement between 2 devices, they will issues addresses from identical configured pools.

My advice - keep the DHCP on 1 device.

JMTPW

[Jon Marshall · Accepted solution]

ajaychauhan wrote:
Hi,
Can we enabled DHCP on both core switches ? how would redundancy will take place please explain if its possible.
Thanks
Ajay 

Ajay

Agree with Andrew, core switches are probably not the best for running any type of extra services such as DHCP.

If you do you can achieve redundancy by splitting up the subnet between switches ie.

192.168.5.0 255.255.255.0

default-gateway - 192.168.5.1

switch1

DHCP pool = 192.168.5.1 - 127

subnet mask = 255.255.255.0

DG = 192.168.5.1

switch 2

DHCP pool = 192.168.5.128 - 254

subnet mask = 255.255.255.0

DG = 192.168.5.1

key thing to note is subnet mask and DG are same for both scopes.

This only really gives you redundancy if you can provide an address for all clients in that subnet from either switch so if you have 192.168.5.0/24 then you need to make sure you have 126 clients or less in that vlan. That way if a switch goes down there are still enough addresses on the other switch for all clients in that vlan.

Jon

[ajay chauhan]

Thanks a lot both of you