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DHCP relay not working when same interface is used as listen- and downstream-interface
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I have a couple of VLANs on my site. In VLAN1200 are a DHCP server and clients. Clients in the other VLANs (e.g. VLAN1202) optain IP adresses from DHCP server in VLAN1200 as well. Therefore I have configured DHCP relay agent with listen-interface in VLAN1202 and downstream-interface in VLAN1200 which is working fine so far.

But I also have a DHCP server on a remote site for redundancy which also provides DHCP services for all VLANs of my site. To configure DHCP relay for VLAN1200 to forward packets to the DHCP server in the remote site I have to add VLAN1200 to listen-interface of the relay agent. But when I do this, DHCP relay stops relaying DHCP requests at all.

I guess setting the same interface as listen-interface and downstream-interface is not supported or it is a bug of the ISC dhcrelayd daemon. The dhcrelayd daemon keeps running with this configuration but it simply stops relaying any requests.

If this is not a bug, it would be nice to be able to configure multiple independent DHCP relay instances in VyOS. If this can't be realized with ISC dhcrelayd, maybe a migration to dnsmasq dhcp-relay is a possible solution.

Here is my forum topic as reference.

I am currently running VyOS 1.4-rolling-202307311804 on my router and this is a summary of my configuration:

VLAN Interfaces

ethernet eth1 {
    description INTERNAL
    duplex auto
    hw-id 00:0c:29:3c:ab:a8
    speed auto
    vif 1200 {
        description HN-HH-CLIENTS
    vif 1202 {
        description HN-HH-MGMT-WLAN
    vif 1203 {
        description HN-HH-DMZ-IOT
    vif 1204 {
        description HN-HH-DMZ
    vif 1205 {
        description HN-HH-DMZ-GUESTS
    vif 1280 {
        description HN-HH-VPN-TRANSFER

DHCP Relay

listen-interface eth1.1200
listen-interface eth1.1202
listen-interface eth1.1204
listen-interface eth1.1203
listen-interface eth1.1205
relay-options {
    relay-agents-packets discard
upstream-interface eth1.1280
upstream-interface eth1.1200


Difficulty level
Unknown (require assessment)
VyOS 1.4
Why the issue appeared?
Will be filled on close
Is it a breaking change?
Unspecified (possibly destroys the router)
Issue type
Bug (incorrect behavior)