diff --git a/bird-gdb.py b/bird-gdb.py
index a85ef8c6..3cf65a9c 100644
--- a/bird-gdb.py
+++ b/bird-gdb.py
@@ -30,6 +30,7 @@ class BIRDFValPrinter(BIRDPrinter):
             "T_ENUM_ROA": "i",
             "T_ENUM_NETTYPE": "i",
             "T_ENUM_RA_PREFERENCE": "i",
+            "T_ENUM_AF": "i",
             "T_IP": "ip",
             "T_NET": "net",
             "T_STRING": "s",
diff --git a/conf/gen_keywords.m4 b/conf/gen_keywords.m4
index cf3fb58e..0c1dc545 100644
--- a/conf/gen_keywords.m4
+++ b/conf/gen_keywords.m4
@@ -34,9 +34,11 @@ m4_define(CF_CLI, `CF_KEYWORDS(m4_translit($1, [[ ]], [[,]]))
 ')
 
 # Enums are translated to C initializers: use CF_ENUM(typename, prefix, values)
-m4_define(CF_enum, `m4_divert(1){ "CF_enum_prefix[[]]$1", -((CF_enum_type<<16) | CF_enum_prefix[[]]$1), NULL },
+# For different prefix: CF_ENUM_PX(typename, external prefix, C prefix, values)
+m4_define(CF_enum, `m4_divert(1){ "CF_enum_prefix_ext[[]]$1", -((CF_enum_type<<16) | CF_enum_prefix_int[[]]$1), NULL },
 m4_divert(-1)')
-m4_define(CF_ENUM, `m4_define([[CF_enum_type]],$1)m4_define([[CF_enum_prefix]],$2)CF_iterate([[CF_enum]], [[m4_shift(m4_shift($@))]])DNL')
+m4_define(CF_ENUM, `m4_define([[CF_enum_type]],$1)m4_define([[CF_enum_prefix_ext]],$2)m4_define([[CF_enum_prefix_int]],$2)CF_iterate([[CF_enum]], [[m4_shift(m4_shift($@))]])DNL')
+m4_define(CF_ENUM_PX, `m4_define([[CF_enum_type]],$1)m4_define([[CF_enum_prefix_ext]],$2)m4_define([[CF_enum_prefix_int]],$3)CF_iterate([[CF_enum]], [[m4_shift(m4_shift(m4_shift($@)))]])DNL')
 
 # After all configuration templates end, we generate the 
 m4_m4wrap(`
diff --git a/conf/gen_parser.m4 b/conf/gen_parser.m4
index af43d96f..5b378a93 100644
--- a/conf/gen_parser.m4
+++ b/conf/gen_parser.m4
@@ -44,6 +44,7 @@ m4_define(CF_CLI_HELP, `')
 
 # ENUM declarations are ignored
 m4_define(CF_ENUM, `')
+m4_define(CF_ENUM_PX, `')
 
 # After all configuration templates end, we finally generate the grammar file.
 m4_m4wrap(`
diff --git a/filter/data.h b/filter/data.h
index 083595f4..db6b6e12 100644
--- a/filter/data.h
+++ b/filter/data.h
@@ -38,6 +38,7 @@ enum f_type {
   T_ENUM_ROA = 0x35,
   T_ENUM_NETTYPE = 0x36,
   T_ENUM_RA_PREFERENCE = 0x37,
+  T_ENUM_AF = 0x38,
 
 /* new enums go here */
   T_ENUM_EMPTY = 0x3f,	/* Special hack for atomic_aggr */
diff --git a/lib/ip.h b/lib/ip.h
index 945f2893..f3b1cc31 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -48,6 +48,13 @@
 #define UDP_HEADER_LENGTH	8
 
 
+/* IANA Address Family Numbers */
+/* https://www.iana.org/assignments/address-family-numbers/address-family-numbers.xhtml */
+/* Would use AF_ prefix, but that collides with POSIX address family numbers */
+#define AFI_IPV4		1
+#define AFI_IPV6		2
+
+
 #ifdef DEBUGGING
 
 typedef struct ip4_addr {
diff --git a/nest/config.Y b/nest/config.Y
index 1bc203dd..8fe060c5 100644
--- a/nest/config.Y
+++ b/nest/config.Y
@@ -85,6 +85,7 @@ CF_ENUM(T_ENUM_RTS, RTS_, DUMMY, STATIC, INHERIT, DEVICE, STATIC_DEVICE, REDIREC
 CF_ENUM(T_ENUM_SCOPE, SCOPE_, HOST, LINK, SITE, ORGANIZATION, UNIVERSE, UNDEFINED)
 CF_ENUM(T_ENUM_RTD, RTD_, UNICAST, BLACKHOLE, UNREACHABLE, PROHIBIT)
 CF_ENUM(T_ENUM_ROA, ROA_, UNKNOWN, VALID, INVALID)
+CF_ENUM_PX(T_ENUM_AF, AF_, AFI_, IPV4, IPV6)
 
 %type <i32> idval
 %type <f> imexport