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What could be the issue if IPv4 fixed addressing not working

ka2tik
Techie
Posts: 1
2027     0

 We have DHCP running and we want to have some IP from DCHP range to be reserved for some hosts, so that IP would not be leased to another device other than reserved host.

What should be the best option to achieve this ?

Tried with fixed addressing but it didn't work as after fixed address with MAC address configuration for one end system, it is getting other DHCP leased IP address rather than the fixed reserved IP.

What could have caused such issue?

Re: What could be the issue if IPv4 fixed addressing not working

Adviser
Posts: 101
2028     0

Are you sure it was exaclty the same MAC address?

 

You can also convert the IP address from the range where the device got its IP to a fixed address after the inital lease has been granted.

 

 

 

 

Re: What could be the issue if IPv4 fixed addressing not working

Moderator bkoshy
Moderator
Posts: 130
2028     0

Hello,

 

New fixed address creation AND fixed address changes are most often required to be written directly to the DHCP configuration file [dhcpd.conf]. Hence any new fixed address creation, changes to existing ones would require you to restart the service on the concerned DHCP server. However, there are features such as "Immediate FA configuration", in NIOS version 7.0 and above which can apply a fixed address without having to restart the dhcp service. Having said that, even if immediate FA configuration is enabled, if the fixed address you are allocating to a MAC address falls in an existing DHCP range, you will have to restart the service for the changes to take effect.

 

Apart from the above, DHCP server most often uses relay agent information (giaddr) for subnet selection for a client. For example: If the Fixed Address you configured is 1.1.1.1 inside 1.1.1.0/24 network and if the client's request for an IP address is via 2.2.2.1 which falls in 2.2.2.0/24 network, your client would end up receiving an IP address from the pool inside 2.2.2.0 network. Having said that, I would like to clarify that subnet selection may not always be associated to relay agent info. Sometimes, it could be on the basis of certain custom configuration such as Option-82, sub-option 5 [Link selection]

Best Regards,
Bibin Thomas

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