diff --git a/conf/confbase.Y b/conf/confbase.Y
index e7fd1677..901ca2b2 100644
--- a/conf/confbase.Y
+++ b/conf/confbase.Y
@@ -27,16 +27,16 @@ CF_HDR
 CF_DEFINES
 
 static void
-check_u16(unsigned val)
+check_u16(uint val)
 {
   if (val > 0xFFFF)
-    cf_error("Value %d out of range (0-65535)", val);
+    cf_error("Value %u out of range (0-65535)", val);
 }
 
 CF_DECLS
 
 %union {
-  int i;
+  uint i;
   u32 i32;
   u64 i64;
   ip_addr a;
@@ -175,7 +175,7 @@ ipa_scope:
 
 pxlen4:
    '/' NUM {
-     if ($2 < 0 || $2 > IP4_MAX_PREFIX_LENGTH) cf_error("Invalid prefix length %d", $2);
+     if ($2 > IP4_MAX_PREFIX_LENGTH) cf_error("Invalid prefix length %u", $2);
      $$ = $2;
    }
  | ':' IP4 {
@@ -196,8 +196,8 @@ net_ip4_: IP4 pxlen4
 
 net_ip6_: IP6 '/' NUM
 {
-  if ($3 < 0 || $3 > IP6_MAX_PREFIX_LENGTH)
-    cf_error("Invalid prefix length %d", $3);
+  if ($3 > IP6_MAX_PREFIX_LENGTH)
+    cf_error("Invalid prefix length %u", $3);
 
   net_fill_ip6(&($$), $1, $3);
 
@@ -223,16 +223,16 @@ net_roa4_: net_ip4_ MAX NUM AS NUM
 {
   $$ = cfg_alloc(sizeof(net_addr_roa4));
   net_fill_roa4($$, net4_prefix(&$1), net4_pxlen(&$1), $3, $5);
-  if ($3 < (int) net4_pxlen(&$1) || $3 > IP4_MAX_PREFIX_LENGTH)
-    cf_error("Invalid max prefix length %d", $3);
+  if ($3 < net4_pxlen(&$1) || $3 > IP4_MAX_PREFIX_LENGTH)
+    cf_error("Invalid max prefix length %u", $3);
 };
 
 net_roa6_: net_ip6_ MAX NUM AS NUM
 {
   $$ = cfg_alloc(sizeof(net_addr_roa6));
   net_fill_roa6($$, net6_prefix(&$1), net6_pxlen(&$1), $3, $5);
-  if ($3 < (int) net6_pxlen(&$1) || $3 > IP6_MAX_PREFIX_LENGTH)
-    cf_error("Invalid max prefix length %d", $3);
+  if ($3 < net6_pxlen(&$1) || $3 > IP6_MAX_PREFIX_LENGTH)
+    cf_error("Invalid max prefix length %u", $3);
 };
 
 net_ip_: net_ip4_ | net_ip6_ ;
diff --git a/filter/config.Y b/filter/config.Y
index 2864d290..a64bb932 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -728,8 +728,8 @@ fprefix:
  | net_ip_ '-'	{ $$.net = $1; $$.lo = 0; $$.hi = $1.pxlen; }
  | net_ip_ '{' NUM ',' NUM '}' {
      $$.net = $1; $$.lo = $3; $$.hi = $5;
-     if ((0 > $3) || ($3 > $5) || ($5 > net_max_prefix_length[$1.type]))
-       cf_error("Invalid prefix pattern range: {%d, %d}", $3, $5);
+     if (($3 > $5) || ($5 > net_max_prefix_length[$1.type]))
+       cf_error("Invalid prefix pattern range: {%u, %u}", $3, $5);
    }
  ;
 
diff --git a/filter/filter.h b/filter/filter.h
index 0beac679..6c81b9bc 100644
--- a/filter/filter.h
+++ b/filter/filter.h
@@ -19,11 +19,11 @@ struct f_inst {		/* Instruction */
   u16 code;		/* Instruction code, see the interpret() function and P() macro */
   u16 aux;		/* Extension to instruction code, T_*, EA_*, EAF_*  */
   union {
-    int i;
+    uint i;
     void *p;
   } a1;			/* The first argument */
   union {
-    int i;
+    uint i;
     void *p;
   } a2;			/* The second argument */
   int lineno;
diff --git a/nest/config.Y b/nest/config.Y
index e672d730..220fa8b0 100644
--- a/nest/config.Y
+++ b/nest/config.Y
@@ -349,8 +349,8 @@ iface_patt:
  ;
 
 tos:
-   CLASS expr { $$ = $2 & 0xfc;        if (($2 < 0) || ($2 > 255)) cf_error("TX class must be in range 0-255"); }
- | DSCP expr  { $$ = ($2 & 0x3f) << 2; if (($2 < 0) || ($2 > 63))  cf_error("TX DSCP must be in range 0-63"); }
+   CLASS expr { $$ = $2 & 0xfc;        if ($2 > 255) cf_error("TX class must be in range 0-255"); }
+ | DSCP expr  { $$ = ($2 & 0x3f) << 2; if ($2 > 63)  cf_error("TX DSCP must be in range 0-63"); }
  ;
 
 /* Direct device route protocol */
diff --git a/proto/ospf/config.Y b/proto/ospf/config.Y
index 9cfc70a9..1f379bf4 100644
--- a/proto/ospf/config.Y
+++ b/proto/ospf/config.Y
@@ -126,7 +126,7 @@ static inline void
 ospf_check_defcost(int cost)
 {
   if ((cost <= 0) || (cost >= LSINFINITY))
-   cf_error("Default cost must be in range 1-%d", LSINFINITY-1);
+   cf_error("Default cost must be in range 1-%u", LSINFINITY-1);
 }
 
 static inline void
@@ -185,10 +185,10 @@ ospf_proto_item:
  | RFC1583COMPAT bool { OSPF_CFG->rfc1583 = $2; }
  | STUB ROUTER bool { OSPF_CFG->stub_router = $3; }
  | ECMP bool { OSPF_CFG->ecmp = $2 ? OSPF_DEFAULT_ECMP_LIMIT : 0; }
- | ECMP bool LIMIT expr { OSPF_CFG->ecmp = $2 ? $4 : 0; if ($4 < 0) cf_error("ECMP limit cannot be negative"); }
+ | ECMP bool LIMIT expr { OSPF_CFG->ecmp = $2 ? $4 : 0; }
  | MERGE EXTERNAL bool { OSPF_CFG->merge_external = $3; }
- | TICK expr { OSPF_CFG->tick = $2; if($2<=0) cf_error("Tick must be greater than zero"); }
- | INSTANCE ID expr { OSPF_CFG->instance_id = $3; if (($3<0) || ($3>255)) cf_error("Instance ID must be in range 0-255"); }
+ | TICK expr { OSPF_CFG->tick = $2; if($2 <= 0) cf_error("Tick must be greater than zero"); }
+ | INSTANCE ID expr { OSPF_CFG->instance_id = $3; if ($3 > 255) cf_error("Instance ID must be in range 0-255"); }
  | ospf_area
  ;
 
@@ -318,7 +318,7 @@ ospf_iface_item:
  | REAL BROADCAST bool { OSPF_PATT->real_bcast = $3; if (!ospf_cfg_is_v2()) cf_error("Real broadcast option requires OSPFv2"); }
  | PTP NETMASK bool { OSPF_PATT->ptp_netmask = $3; if (!ospf_cfg_is_v2()) cf_error("PtP netmask option requires OSPFv2"); }
  | TRANSMIT DELAY expr { OSPF_PATT->inftransdelay = $3 ; if (($3<=0) || ($3>65535)) cf_error("Transmit delay must be in range 1-65535"); }
- | PRIORITY expr { OSPF_PATT->priority = $2 ; if (($2<0) || ($2>255)) cf_error("Priority must be in range 0-255"); }
+ | PRIORITY expr { OSPF_PATT->priority = $2 ; if ($2>255) cf_error("Priority must be in range 0-255"); }
  | STRICT NONBROADCAST bool { OSPF_PATT->strictnbma = $3 ; }
  | STUB bool { OSPF_PATT->stub = $2 ; }
  | CHECK LINK bool { OSPF_PATT->check_link = $3; }
@@ -404,7 +404,7 @@ ospf_iface_start:
 
 ospf_instance_id:
    /* empty */
- | INSTANCE expr { OSPF_PATT->instance_id = $2; if (($2<0) || ($2>255)) cf_error("Instance ID must be in range 0-255"); }
+ | INSTANCE expr { OSPF_PATT->instance_id = $2; if ($2 > 255) cf_error("Instance ID must be in range 0-255"); }
  ;
 
 ospf_iface_patt_list:
diff --git a/proto/radv/config.Y b/proto/radv/config.Y
index 7ba23205..b5f4b5f2 100644
--- a/proto/radv/config.Y
+++ b/proto/radv/config.Y
@@ -91,14 +91,14 @@ radv_iface_item:
  | MIN DELAY expr { RADV_IFACE->min_delay = $3; if ($3 <= 0) cf_error("Min delay must be positive"); }
  | MANAGED bool { RADV_IFACE->managed = $2; }
  | OTHER CONFIG bool { RADV_IFACE->other_config = $3; }
- | LINK MTU expr { RADV_IFACE->link_mtu = $3; if ($3 < 0) cf_error("Link MTU must be 0 or positive"); }
- | REACHABLE TIME expr { RADV_IFACE->reachable_time = $3; if (($3 < 0) || ($3 > 3600000)) cf_error("Reachable time must be in range 0-3600000"); }
- | RETRANS TIMER expr { RADV_IFACE->retrans_timer = $3; if ($3 < 0) cf_error("Retrans timer must be 0 or positive"); }
- | CURRENT HOP LIMIT expr { RADV_IFACE->current_hop_limit = $4; if (($4 < 0) || ($4 > 255))  cf_error("Current hop limit must be in range 0-255"); }
+ | LINK MTU expr { RADV_IFACE->link_mtu = $3; }
+ | REACHABLE TIME expr { RADV_IFACE->reachable_time = $3; if ($3 > 3600000) cf_error("Reachable time must be in range 0-3600000"); }
+ | RETRANS TIMER expr { RADV_IFACE->retrans_timer = $3; }
+ | CURRENT HOP LIMIT expr { RADV_IFACE->current_hop_limit = $4; if ($4 > 255) cf_error("Current hop limit must be in range 0-255"); }
  | DEFAULT LIFETIME expr radv_sensitive {
      RADV_IFACE->default_lifetime = $3;
-     if (($3 < 0) || ($3 > 9000))  cf_error("Default lifetime must be in range 0-9000");
-     if ($4 != -1) RADV_IFACE->default_lifetime_sensitive = $4;
+     if ($3 > 9000)  cf_error("Default lifetime must be in range 0-9000");
+     if ($4 != (uint) -1) RADV_IFACE->default_lifetime_sensitive = $4;
    }
  | DEFAULT PREFERENCE radv_preference { RADV_IFACE->default_preference = $3; }
  | PREFIX radv_prefix { add_tail(&RADV_IFACE->pref_list, NODE this_radv_prefix); }
@@ -125,7 +125,7 @@ radv_iface_finish:
 
   if ((ic->min_ra_int > 3) &&
       (ic->min_ra_int > (ic->max_ra_int * 3 / 4)))
-    cf_error("Min RA interval must be at most 3/4 * Max RA interval %d %d", ic->min_ra_int, ic->max_ra_int);
+    cf_error("Min RA interval must be at most 3/4 * Max RA interval");
 
   if ((ic->default_lifetime > 0) && (ic->default_lifetime < ic->max_ra_int))
     cf_error("Default lifetime must be either 0 or at least Max RA interval");
@@ -163,13 +163,11 @@ radv_prefix_item:
  | AUTONOMOUS bool { RADV_PREFIX->autonomous = $2; }
  | VALID LIFETIME expr radv_sensitive {
      RADV_PREFIX->valid_lifetime = $3;
-     if ($3 < 0) cf_error("Valid lifetime must be 0 or positive");
-     if ($4 != -1) RADV_PREFIX->valid_lifetime_sensitive = $4;
+     if ($4 != (uint) -1) RADV_PREFIX->valid_lifetime_sensitive = $4;
    }
  | PREFERRED LIFETIME expr radv_sensitive {
      RADV_PREFIX->preferred_lifetime = $3;
-     if ($3 < 0) cf_error("Preferred lifetime must be 0 or positive");
-     if ($4 != -1) RADV_PREFIX->preferred_lifetime_sensitive = $4;
+     if ($4 != (uint) -1) RADV_PREFIX->preferred_lifetime_sensitive = $4;
    }
  ;
 
diff --git a/proto/rip/config.Y b/proto/rip/config.Y
index 25c2ac7a..46f6c177 100644
--- a/proto/rip/config.Y
+++ b/proto/rip/config.Y
@@ -65,7 +65,7 @@ rip_proto_item:
    proto_item
  | proto_channel
  | ECMP bool		{ RIP_CFG->ecmp = $2 ? RIP_DEFAULT_ECMP_LIMIT : 0; }
- | ECMP bool LIMIT expr	{ RIP_CFG->ecmp = $2 ? $4 : 0; if ($4 < 0) cf_error("ECMP limit cannot be negative"); }
+ | ECMP bool LIMIT expr	{ RIP_CFG->ecmp = $2 ? $4 : 0; }
  | INFINITY expr	{ RIP_CFG->infinity = $2; }
  | INTERFACE rip_iface
  ;