DHCPACK question

[Jack Kielsmeier]

Howdy!

The requests you see coming from the gateway address are client
broadcast DHCP requests hitting your gateway. Your gateway then forwards
that onto your DHCP server via it's DHCP helper address function.

Once a client receives an IP, it notes the DHCP server address and will
request IP renewal from your DHCP server directly rather than sending
out a broadcast.

To put it more simply, when a machine doesn't have an IP, it'll send a
broadcast out to get one, your gateway/router which is on the same
network as the client, will see the broadcast and then direct the
request to the DHCP server.

Once the client has an IP, it knows the IP address of the DHCP server
and will communicate directly with it to renew it's lease.
-- 
Jack Kielsmeier <jackkiel at netins.net>

> 
> Probably a silly question but since I don't deal with DHCP much I will ask anyway.
> I am doing some troubleshooting and I noticed in the logs that DHCPACK sometimes
> gets requested via the gateway and other times via eth0. Why would that be?
> 
> Here is an example of the log
> 
> Feb 12 08:34:15 net1 dhcpd: Added new forward map from it022402.domain.co.nz. to 205.118.130.186
> Feb 12 08:34:15 net1 dhcpd: DHCPREQUEST for 205.118.130.186 from 00:0d:5e:82:75:d1 (IT022402) via 205.118.130.129
> Feb 12 08:34:15 net1 dhcpd: DHCPACK on 205.118.130.186 to 00:0d:5e:82:75:d1 (IT022402) via 205.118.130.129
> Feb 12 08:35:18 net1 dhcpd: DHCPINFORM from 205.118.130.186 via 205.118.130.129
> Feb 12 08:35:18 net1 dhcpd: DHCPACK to 205.118.130.186 (00:0d:5e:82:75:d1) via eth0
> Feb 12 08:35:21 net1 dhcpd: DHCPINFORM from 205.118.130.186 via 205.118.130.129
> Feb 12 08:35:21 net1 dhcpd: DHCPACK to 205.118.130.186 (00:0d:5e:82:75:d1) via eth0
> 
> Feb 12 09:55:44 net1 dhcpd: Added new forward map from it022555.mydomain.ac.nz. to 205.118.130.200
> Feb 12 09:55:44 net1 dhcpd: DHCPREQUEST for 205.118.130.200 from 00:14:c2:06:3e:a3 via 205.118.130.129
> Feb 12 09:55:44 net1 dhcpd: DHCPACK on 205.118.130.200 to 00:14:c2:06:3e:a3 (it022555) via 205.118.130.129
> Feb 12 11:08:40 net1 dhcpd: Added new forward map from it022555.massey.ac.nz. to 205.118.130.200
> Feb 12 11:08:40 net1 dhcpd: DHCPREQUEST for 205.118.130.200 from 00:14:c2:06:3e:a3 (it022555) via eth0
> Feb 12 11:08:40 net1 dhcpd: DHCPACK on 205.118.130.200 to 00:14:c2:06:3e:a3 (it022555) via eth0
> 
> cheers
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