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Community Member

SLB Does this to me?

Hello Experts!

I Have 1 DHCP Server WHICH Provide IPs to all my network computers this DHCP Represent a Single Point failure ,i need to make redundany for this server in case the 1st DHCP Goes Down the new 2nd 1 takes Over.this DHCP IS Connected to CORE 6509 SUP 7209 IOS:(72033-jk9sv-mz.122-18.SXD5.bin)

Does SLB achieve this for me?if so tell me the Procedure

10xs

6 REPLIES
Cisco Employee

Re: SLB Does this to me?

No Ali SLB will not do that. What you eventually need is 2 DHCP servers in your LAN with the same DHCP pools configured on them. Then under the SVI on your core 6509 define two " ip-helper addresses " for both the servers. The DHCP request will be sent to both the servers and which one replies first, the client will get the IP address from the same. If one of the DHCP server goes down the other one wil take care of it.

Here is what you have to do :

Config t

Int Vlan 1

Ip address x.x.x.1 y.y.y.0

ip-helper address a.a.a.a

ip-helper address b.b.b.b

Int Vlan 2

Ip address c.c.c.1 d.d.d.0

ip-helper address a.a.a.a

ip-helper address b.b.b.b

You dont have to put the ip-helper address on the Vlan interface where your DHCp servers are connected.

HTH,

-amit singh

Hall of Fame Super Blue

Re: SLB Does this to me?

Hi Ali

You can use another "ip helper-address" statement under your L3 interfaces eg

if your existing DHCP server is 192.168.5.10 your config would look something like

vlan 10

ip address 192.168.6.1 255.255.255.0

ip helper-address 192.168.5.10

If you add another DHCP server into your network eg 192.168.5.11 just add this under all your vlan interface that already have ip helper-address commands ie

vlan 10

ip address 192.168.6.1 255.255.255.0

ip helper-address 192.168.5.10

ip helper-address 192.168.5.11

HTH

Jon

Community Member

Re: SLB Does this to me?

Hello

10xs a lot for ur valuable reply

ALI

Cisco Employee

Re: SLB Does this to me?

Hi Ali,

As experts above posted you can use 2 DHCP servers and both will reply to the DHCP request and then it depend on client to which it responds, I will recommend when you configure 2 DHCP servers always configure different not overlapping pool of addresses on your 2 DHCP servers.

HTH

Ankur

Community Member

Re: SLB Does this to me?

Ankur My Freind!

plz give some example regarding ur recommendation.

ALI

Cisco Employee

Re: SLB Does this to me?

Hi Ali,

Because two DHCP servers cannot serve the same addresses, address pools defined for a subnet must be unique across DHCP servers. Therefore, when using two or more DHCP servers to serve a particular subnet, the complete list of addresses for that subnet must be divided among the servers. For example, you could configure one server with an address pool consisting of 70% of the available addresses for the subnet and the other server with an address pool consisting of the remaining 30% of the available addresses.

Using multiple DHCP servers decreases the probability of having a DHCP-related network access failure, but it does not guarantee against it. If a DHCP server for a particular subnet fails, the other DHCP server may not be able to service all the requests from new clients which may, for example, use up the server's limited pool of available addresses.

If you are considering multiple DHCP servers, remember that multiple DHCP servers cannot share any of the same addresses. If you use more than one DHCP server in your network, each server must be configured with their own unique IP address ranges.

HTH

Ankur

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