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I want to setup a cisco router to be a DHCP relay but i want to answer dhcp requests locally if the DHCP Relay request won't answer.

In the other word, I want to setup a dhcp relay with fail safe(Which assign ip from its own DHCP pool)

Ali
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1 Answers1

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You can do that with an event and an ip sla to remove the commands on the failover detection. From there I'd configure conflict detection on your primary DHCP, and possibly split scope as defined in the article below.

The below example would probably need to be modified slightly but should work simply enough.

ip sla 10

icmp-echo DHCP-SERVER-IP

timeout 200

frequency 5

ip sla schedule 10 life forever start-time now

track 1 rtr 10 reachability

event manager applet PRIMARY-DHCP-OFFLINE

event track 1 state down

action 5.0 cli command "enable"

action 5.1 cli command "conf t"

action 5.3 cli command "ip dhcp excluded-address 10.10.10.1"

action 5.4 cli command "ip dhcp pool backup"

action 5.5 cli command "network 10.10.10.1 255.255.255.0"

action 5.6 cli command "default-router 10.10.10.1"

action 5.7 cli command "lease 0 12"

action 5.8 cli command "exit"

action 5.9 cli command "end"


event manager applet PRIMARY-DHCP-ONLINE

event track 1 state up

action 6.0 cli command "enable"

action 6.1 cli command "conf t"

action 6.2 cli command "no ip dhcp pool backup"

action 6.3 cli command "no ip dhcp excluded-address 10.10.10.1"

action 6.4 cli command "end"

If your primary DHCP server is windows the below article for configuring split scope which would ensure the server doesn't tromp over any IPs the DHCP

https://blogs.technet.microsoft.com/teamdhcp/2009/01/22/how-to-configure-split-scope-using-wizard/

You would also want to configure duplicate IP detection on windows just in case as well.

https://technet.microsoft.com/en-us/library/dd183587(v=ws.10).aspx

PHELMS
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