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Feature #11990

DHCP client support for "Classless Static Route" option

Added by Joshua M. Clulow 5 months ago.

Status:
New
Priority:
Normal
Category:
networking
Start date:
Due date:
% Done:

0%

Estimated time:
Difficulty:
Medium
Tags:

Description

RFC 3442 describes a DHCP option used to provide a static route entry to the client. This option is quite flexible, and allows for both next-hop style routes (where a prefix is directed through a locally accessible gateway) and for local routes (where an off-subnet host is described as being directly accessible).

Google Compute Engine (GCE) uses a somewhat eccentric network configuration, which it describes to the guest using this DHCP option. In particular, the DHCP server provides a 32 bit subnet mask; i.e., there are no on-subnet hosts. The DHCP server then provides a classless route option for an off-subnet gateway IP, and a default gateway entry using that off-subnet IP.

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