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DHCP Relay upstream and downstream interfaces
Open, NormalPublicENHANCEMENT

Description

This is based on the T1276

Currently, the dhcp-relay service requires to specify both upstream and downstream interfaces to make the service working. There is no distinction for them in VyOS config syntax and in the isc-dhcp-relay config file.
Additionally, the current config syntax is not understandable for many users, especially for those who are used to Cisco or HP approach (ip helper set per L3 interface). They often ask why do they need to add DHCP server facing interfaces into the relay config.
Another drawback is that the current config makes the relay to generate an extra and needless DHCP REQUEST packet with a wrong address set in the giaddr field (details in T1276).

Current syntax and config file:

show service 
 dhcp-relay {
     interface eth0
     interface eth1
     relay-options {
         relay-agents-packets discard
     }
     server 172.16.0.254
 }
# On what interfaces should the DHCP relay (dhrelay) serve DHCP requests?
INTERFACES="eth0 eth1"

# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-4 -a -m discard"

Proposed change:

show service 
 dhcp-relay {
     upstream-interface eth0
     downstream-interface eth1
     relay-options {
         relay-agents-packets discard
     }
     server 172.16.0.254
 }
# On what interfaces should the DHCP relay (dhrelay) serve DHCP requests?
INTERFACES=""

# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-4 -a -m discard -id eth0 -iu eth1"

IMPORTANT NOTE: the isc-dhcp-relay allows to differentiate between downstream and upstream interfaces since v4.3.5. Therefor, this change could be easily introduce into VyOS 1.3. For v1.2, the isc-dhcp-relay package upgrade would be required and I'm not sure if that is possible.

Details

Difficulty level
Unknown (require assessment)
Version
-
Why the issue appeared?
Will be filled on close
Is it a breaking change?
Config syntax change (migratable)

Event Timeline

g.skupien triaged this task as Normal priority.Apr 30 2020, 7:15 PM
g.skupien created this task.
pasik added a subscriber: pasik.May 1 2020, 10:35 AM