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FMC DHCP Relay Error

While I was trying to configure DHCP Relay on an FTD the other day, I was stuck for a while with the Error : DHCP: Interface 'inside' is currently configured as CLIENT... . The exact error is below, and that was happening every time I was trying to deploy the configs on the FMC:

Error : DHCP: Interface 'inside' is currently configured as CLIENT and cannot be changed to a RELAY SERVER by a RELAY feature

Surfing the web trying to find a fix, a few posts where talking about disabling the call-home feature. However, I could not find a way to do this through FMC. And to be honest, I was not a 100% sure how the call-home would affect DHCP Relay.

The error I was getting was clearly stating the inside interface was configured as a DHCP client. But the interface was assigned with a static IP address. On that FTD box I had AnyConnect configured and one of the options was to use an internal DHCP server via the inside interface. So, under the AnyConnect tunnel group general-attributes I had the command dhcp-server applied. So I thought that would have been the issue then. I removed that command but did not really help.

I was left with no options apart from reloading the FTD. After the reload, I tried to configure the DHCP Relay and it worked. So, I said, it must have been something to do with the dhcp-server command I removed. To try to reproduce the issue, I removed the DHCP Relay configs, and then added again the dhcp-server command. And then added again the DHCP Relay and it worked.

That for me did not make any sense, and I think the main reason why it was not working would be due to some software bug. In fact, surfing the web, I could find a similar reported bug. Although it was not exactly the same, but for me it seemed that the FTD I was working on was hitting a similar bug.

Here is the snippet of the call-home and DHCP Relay configs from my FTD:

ftdv-03# sh run | be call
profile CiscoTAC-1
no active
destination address http
destination address email
destination transport-method http
subscribe-to-alert-group diagnostic
subscribe-to-alert-group environment
subscribe-to-alert-group inventory periodic monthly
subscribe-to-alert-group configuration periodic monthly
subscribe-to-alert-group telemetry periodic daily
snort preserve-connection
: end
ftdv-03# sh run dhcprelay
dhcprelay server outside
dhcprelay enable inside
dhcprelay timeout 60

As you can see, in the end the call-home feature and the DHCP Relay can coexist together. I had already covered DHCP Relay configuration on FMC in this previous post. Take a look if you want to read more about it.

This wraps this post on Error : DHCP: Interface 'inside' is currently configured as CLIENT and cannot be changed to a RELAY SERVER by a RELAY feature.

Please let me know if you ever came across a similar situation, and how did you manage to fix it in the comments below.

Thank you for reading!

Posted in Blog, Firepower, FMC, FTD, Security

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