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Webcast-Catalyst9k
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DHCP Pool:

I have two core switches and my customer required the core switch to provide dhcp. Should I configure the dhcp pool on both switches to provide redundancy.

Can someone post an example of this configuration for dhcp pool on both core

switches.

Thanxs.

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: DHCP Pool:

Colm

If the DHCP pool is for a vlan that is directly connected then no you don't. Only if the switch is a DHCP server for clients that are more than 1 hop away would you need an ip helper-address.

"If the pool on the first core is used up, will the clients get there ip address from the second core switch?"

Should do because each switch will see a DHCP request from the client, providing your core switches are connected via a L2 link that includes that vlan.

Jon

3 REPLIES
Hall of Fame Super Blue

Re: DHCP Pool:

Colm

You can't configure the same pool on both switches because the switches don't communicate so they could hand out the same addresses. What you can do is configure half the pool on one switch and the other half on the the other switch.

If you choose a big enough pool then half the pool should be enough for all your clients. ON each switch you would need to exclude the IP's used on the other switch eg.

DHCP pool 192.168.5.0/24

on switch 1

ip dhcp excluded-address 192.168.5.129 192.168.5.254

ip dhcp pool SW1

network 192.168.5.0 /24

default-router 192.168.5.1

on switch 1

ip dhcp excluded-address 192.168.5.1 192.168.5.128

ip dhcp pool SW1

network 192.168.5.0 /24

default-router 192.168.5.129

See this link for all options in DHCP setup -

http://www.cisco.com/en/US/docs/ios/ipaddr/configuration/guide/iad_dhcp_svr_cfg_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1046221

Jon

New Member

Re: DHCP Pool:

Thanks Jon.

Do I need to add an ip helper-addresss under the SVI on each core switch?

If the pool on the first core is used up, will the clients get there ip address from the second core switch?

Hall of Fame Super Blue

Re: DHCP Pool:

Colm

If the DHCP pool is for a vlan that is directly connected then no you don't. Only if the switch is a DHCP server for clients that are more than 1 hop away would you need an ip helper-address.

"If the pool on the first core is used up, will the clients get there ip address from the second core switch?"

Should do because each switch will see a DHCP request from the client, providing your core switches are connected via a L2 link that includes that vlan.

Jon

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