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Bug #16806

open

DHCP client sends packets to the wrong interface with Multi-WAN

Added by Nazar Mokrynskyi 1 day ago. Updated 1 day ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
DHCP (IPv4)
Target version:
-
Start date:
Due date:
% Done:

0%

Estimated time:
Plus Target Version:
Release Notes:
Default
Affected Version:
2.8.1
Affected Architecture:

Description

I have ix0 parent interface with 3 VLANs, one for each ISP: 10 (WAN), 20 (WAN2) and 30 (WAN3).
All ISPs use DHCP to assign IP addresses.

The issue is that pfSense often sends DHCP requests through the wrong interface.
For example, it sends packets from WAN2 IP address to WAN2's gateway, but using WAN interface (confirmed by doing packet capture both on the ix0.10 and on ix0 with VLAN 10).
Naturally, this causes DHCP issues on top of other unresolved DHCP client bugs I have been struggling with over the years.

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 #1

Updated by Nazar Mokrynskyi 1 day ago

I narrowed it down to broadcast working correctly, while unicast not working correctly.

This it caused by dhclient not installing routes for `dhcp-server-identifier` returned by DHCP server when DHCP server and gateway are on different subnets.
As the result, unicast packets go through the default gateway instead of the correct interface.

I bet this is also fixed upstream like https://redmine.pfsense.org/issues/14604, but the version included in pfSense/FreeBSD is ancient and not spec-compliant.

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