7005 questions

8390 answers

13623 comments

10299 members

0 votes
110 views 3 comments
by
Hi all,

unfortunately I did not find anything in the manuals. Does the DHCP server check if an IP is already in use by a device with a static IP prior to assigning it?

I know the question sounds a bit silly but I might be facing a situation where this could happen.

Thx!

1 Answer

0 votes
by
Hello,

It's a bit odd that you are experiencing this. But mostly when the IP address leased it will be in the ARP Table and DHCP Leases. May I know if you are configuring it on the static lease option or you are just putting the IP address manually?  Also is the subnet mask correct? Could you explain it more in details :)

Regards,
Jerome
by

From dnsmasq's FAQ:

Q: Does the dnsmasq DHCP server probe addresses before allocating
   them, as recommended in RFC2131?

A: Yes, dynamically allocated IP addresses are checked by sending an
   ICMP echo request (ping). If a reply is received, then dnsmasq
   assumes that the address is in use, and attempts to allocate an
   different address. The wait for a reply is between two and three
   seconds. Because the DHCP server is not re-entrant, it cannot serve
   other DHCP requests during this time. To avoid dropping requests,
   the address probe may be skipped when dnsmasq is under heavy load.
So it does.
Regards,
by

Hi Jerome,

I am very well aware that this weird ;-)

There is a PC connected to the router which needs to have the same IP all the time in order to ensure full functionality. As we have seen issues where Windows somehow ignores a fixed IP. For this reason there could be the additional option to reserve the same IP within the DHCP range. As I have also seen cases where reservations are not pulled correctly these two issues need to be addressed somehow...

Many thanks for the dnsmasq's FAQ except!

BR

by
Hello,

For this such cases like the reserved IP getting occupied and the router is not getting rebooted it is best to get the troubleshoot file and share it with us. So that we can further check what may be causing the issue.

Thank you and have a nice day!

Regards,

Jerome