From c6473d654d9995a45ebc4bf612a610d123a24a54 Mon Sep 17 00:00:00 2001
From: Jeremy Stretch <stretch@packetlife.net>
Date: Fri, 24 Jan 2020 15:03:38 -0500
Subject: [PATCH] Add explanatory text for constants

---
 netbox/dcim/constants.py | 4 +++-
 netbox/ipam/constants.py | 7 +++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/netbox/dcim/constants.py b/netbox/dcim/constants.py
index 0301da7d8..0e05867e4 100644
--- a/netbox/dcim/constants.py
+++ b/netbox/dcim/constants.py
@@ -26,7 +26,7 @@ REARPORT_POSITIONS_MAX = 64
 #
 
 INTERFACE_MTU_MIN = 1
-INTERFACE_MTU_MAX = 32767
+INTERFACE_MTU_MAX = 32767  # Max value of a signed 16-bit integer
 
 VIRTUAL_IFACE_TYPES = [
     InterfaceTypeChoices.TYPE_VIRTUAL,
@@ -49,7 +49,9 @@ NONCONNECTABLE_IFACE_TYPES = VIRTUAL_IFACE_TYPES + WIRELESS_IFACE_TYPES
 #
 
 POWERFEED_VOLTAGE_DEFAULT = 120
+
 POWERFEED_AMPERAGE_DEFAULT = 20
+
 POWERFEED_MAX_UTILIZATION_DEFAULT = 80  # Percentage
 
 
diff --git a/netbox/ipam/constants.py b/netbox/ipam/constants.py
index 22a977371..41075e54a 100644
--- a/netbox/ipam/constants.py
+++ b/netbox/ipam/constants.py
@@ -9,6 +9,11 @@ BGP_ASN_MAX = 2**32 - 1
 # VRFs
 #
 
+# Per RFC 4364 section 4.2, a route distinguisher may be encoded as one of the following:
+#   * Type 0 (16-bit AS number : 32-bit integer)
+#   * Type 1 (32-bit IPv4 address : 16-bit integer)
+#   * Type 2 (32-bit AS number : 16-bit integer)
+# 21 characters are sufficient to convey the longest possible string value (255.255.255.255:65535)
 VRF_RD_MAX_LENGTH = 21
 
 
@@ -42,6 +47,7 @@ IPADDRESS_ROLES_NONUNIQUE = (
 # VLANs
 #
 
+# 12-bit VLAN ID (values 0 and 4095 are reserved)
 VLAN_VID_MIN = 1
 VLAN_VID_MAX = 4094
 
@@ -50,5 +56,6 @@ VLAN_VID_MAX = 4094
 # Services
 #
 
+# 16-bit port number
 SERVICE_PORT_MIN = 1
 SERVICE_PORT_MAX = 65535