# isc-dhcpd binding to all interfaces despite dhcpd_ifaces="igb0"



## jem (Nov 3, 2020)

I'm running net/isc-dhcp44-server on my FreeBSD router host, providing DHCP service to four VLANs.  _igb0_ is the main network that most devices connect to, while _igb0.128_, _igb0.192_ and _igb0.193_ are my lab VLANs.  I was specifying `dhcpd_ifaces="igb0 igb0.128 igb0.192 igb0.193"` in /etc/rc.conf.local and all was fine.

I now want to have a play with the net/kea DHCP server, but without causing disruption on the main network.  To that end, I am trying to limit isc-dhcpd to providing service only on that network by changing the `dhcpd_ifaces=` to just `"igb0"`, so that I can run Kea on the other VLAN interfaces.  `ps` confirms that dhcpd is now running with just the igb0 interface at the end of the list of arguments, and when I start the service it outputs:


```
Listening on BPF/igb0/00:30:18:03:0f:28/10.0.0.0/24
Sending on   BPF/igb0/00:30:18:03:0f:28/10.0.0.0/24
```

However, `sockstat` indicates that dhcpd is still binding to *:67 and blocking me from running Kea DHCP on the other VLAN interfaces.  Anyone know why this is and how to resolve it?


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## mickey (Nov 3, 2020)

jem said:


> However, `sockstat` indicates that dhcpd is still binding to *:67 and blocking me from running Kea DHCP on the other VLAN interfaces.  Anyone know why this is and how to resolve it?


I'd say that is part of dhcpd's normal operation and being able to receive DHCP broadcast packets. I am seeing the exact same behaviour with only two interfaces specified.

```
Normally a DHCPv4 server will open a raw UDP socket to receive and send
       most DHCPv4 packets.  It also opens a fallback UDP socket for use in
       sending unicast packets.  Normally these will both use the well known
       port number for BOOTPS.
```
You could probably set up a test server running net/kea on a different machine, without the two servers interfering with each other, if they are both properly configured.


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