diff --git a/sys/net/network_layer/fib/fib.c b/sys/net/network_layer/fib/fib.c
index b9cf05ce55..72037141df 100644
--- a/sys/net/network_layer/fib/fib.c
+++ b/sys/net/network_layer/fib/fib.c
@@ -669,9 +669,9 @@ int fib_sr_create(fib_table_t *table, fib_sr_t **fib_sr, kernel_pid_t sr_iface_i
 * @brief Internal function:
 *        checks the lifetime and removes the entry in case it expired
 */
-static int fib_sr_check_lifetime(fib_sr_t *fib_sr, uint64_t *now)
+static int fib_sr_check_lifetime(fib_sr_t *fib_sr)
 {
-    uint64_t tm = fib_sr->sr_lifetime - *now;
+    uint64_t tm = fib_sr->sr_lifetime - xtimer_now64();
     /* check if the lifetime expired */
     if ((int64_t)tm < 0) {
         /* remove this sr if its lifetime expired */
@@ -731,8 +731,6 @@ static int fib_is_sr_in_table(fib_table_t *table, fib_sr_t *fib_sr)
 int fib_sr_read_head(fib_table_t *table, fib_sr_t *fib_sr, kernel_pid_t *iface_id,
                      uint32_t *sr_flags, uint32_t *sr_lifetime)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (iface_id == NULL) || (sr_flags == NULL)
         || (sr_lifetime == NULL) || (fib_is_sr_in_table(table, fib_sr) == -ENOENT) ) {
@@ -740,14 +738,14 @@ int fib_sr_read_head(fib_table_t *table, fib_sr_t *fib_sr, kernel_pid_t *iface_i
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
 
     *iface_id = fib_sr->sr_iface_id;
     *sr_flags = fib_sr->sr_flags;
-    *sr_lifetime = fib_sr->sr_lifetime - now;
+    *sr_lifetime = fib_sr->sr_lifetime - xtimer_now64();
 
     mutex_unlock(&(table->mtx_access));
     return 0;
@@ -756,8 +754,6 @@ int fib_sr_read_head(fib_table_t *table, fib_sr_t *fib_sr, kernel_pid_t *iface_i
 int fib_sr_read_destination(fib_table_t *table, fib_sr_t *fib_sr,
                             uint8_t *dst, size_t *dst_size)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (dst == NULL) || (dst_size == NULL)
         || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
@@ -765,7 +761,7 @@ int fib_sr_read_destination(fib_table_t *table, fib_sr_t *fib_sr,
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -787,15 +783,13 @@ int fib_sr_read_destination(fib_table_t *table, fib_sr_t *fib_sr,
 int fib_sr_set(fib_table_t *table, fib_sr_t *fib_sr, kernel_pid_t *sr_iface_id,
                uint32_t *sr_flags, uint32_t *sr_lifetime)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
         mutex_unlock(&(table->mtx_access));
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -842,8 +836,6 @@ int fib_sr_delete(fib_table_t *table, fib_sr_t *fib_sr)
 
 int fib_sr_next(fib_table_t *table, fib_sr_t *fib_sr, fib_sr_entry_t **sr_path_entry)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (sr_path_entry == NULL)
         || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
@@ -856,7 +848,7 @@ int fib_sr_next(fib_table_t *table, fib_sr_t *fib_sr, fib_sr_entry_t **sr_path_e
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -883,8 +875,6 @@ int fib_sr_next(fib_table_t *table, fib_sr_t *fib_sr, fib_sr_entry_t **sr_path_e
 int fib_sr_search(fib_table_t *table, fib_sr_t *fib_sr, uint8_t *addr, size_t addr_size,
                   fib_sr_entry_t **sr_path_entry)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (addr == NULL) || (sr_path_entry == NULL)
         || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
@@ -892,7 +882,7 @@ int fib_sr_search(fib_table_t *table, fib_sr_t *fib_sr, uint8_t *addr, size_t ad
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -918,8 +908,6 @@ int fib_sr_search(fib_table_t *table, fib_sr_t *fib_sr, uint8_t *addr, size_t ad
 int fib_sr_entry_append(fib_table_t *table, fib_sr_t *fib_sr,
                         uint8_t *addr, size_t addr_size)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (addr == NULL)
         || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
@@ -927,7 +915,7 @@ int fib_sr_entry_append(fib_table_t *table, fib_sr_t *fib_sr,
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -965,8 +953,6 @@ int fib_sr_entry_add(fib_table_t *table, fib_sr_t *fib_sr,
                      fib_sr_entry_t *sr_path_entry, uint8_t *addr, size_t addr_size,
                      bool keep_remaining_route)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (sr_path_entry == NULL) || (addr == NULL)
         || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
@@ -974,7 +960,7 @@ int fib_sr_entry_add(fib_table_t *table, fib_sr_t *fib_sr,
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -1023,15 +1009,13 @@ int fib_sr_entry_add(fib_table_t *table, fib_sr_t *fib_sr,
 int fib_sr_entry_delete(fib_table_t *table, fib_sr_t *fib_sr, uint8_t *addr, size_t addr_size,
                         bool keep_remaining_route)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
         mutex_unlock(&(table->mtx_access));
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -1075,8 +1059,6 @@ int fib_sr_entry_overwrite(fib_table_t *table, fib_sr_t *fib_sr,
                            uint8_t *addr_old, size_t addr_old_size,
                            uint8_t *addr_new, size_t addr_new_size)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (addr_old == NULL) || (addr_new == NULL)
         || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
@@ -1084,7 +1066,7 @@ int fib_sr_entry_overwrite(fib_table_t *table, fib_sr_t *fib_sr,
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -1127,15 +1109,13 @@ int fib_sr_entry_overwrite(fib_table_t *table, fib_sr_t *fib_sr,
 int fib_sr_entry_get_address(fib_table_t *table, fib_sr_t *fib_sr, fib_sr_entry_t *sr_entry,
                              uint8_t *addr, size_t *addr_size)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
     if ((fib_sr == NULL) || (fib_is_sr_in_table(table, fib_sr) == -ENOENT)) {
         mutex_unlock(&(table->mtx_access));
         return -EFAULT;
     }
 
-    if (fib_sr_check_lifetime(fib_sr, &now) == -ENOENT) {
+    if (fib_sr_check_lifetime(fib_sr) == -ENOENT) {
         mutex_unlock(&(table->mtx_access));
         return -ENOENT;
     }
@@ -1274,8 +1254,6 @@ int fib_sr_get_route(fib_table_t *table, uint8_t *dst, size_t dst_size, kernel_p
                      uint8_t *addr_list, size_t *addr_list_elements, size_t *element_size,
                      bool reverse, fib_sr_t **fib_sr)
 {
-    uint64_t now = xtimer_now64();
-
     mutex_lock(&(table->mtx_access));
 
     if ((dst == NULL) || (sr_iface_id == NULL) || (sr_flags == NULL)
@@ -1292,7 +1270,7 @@ int fib_sr_get_route(fib_table_t *table, uint8_t *dst, size_t dst_size, kernel_p
     /* Case 1 - check if we know a direct route */
     for (size_t i = 0; i < table->size; ++i) {
 
-        if (fib_sr_check_lifetime(&table->data.source_routes->headers[i], &now) == -ENOENT) {
+        if (fib_sr_check_lifetime(&table->data.source_routes->headers[i]) == -ENOENT) {
             /* expired, so skip this sr and remember its position */
             if (check_free_entry == -1) {
                 /* we want to fill up the source routes from the beginning */