I finally found a solution to compile kernel module "bridge" with the same (!) kernel headers I once compiled my kernel with success. Makefile contains the same version of kernel (2.4.20, event the same extraersion -8). But when I try to insert that module into a kernel with insmod I get a lot of errors. Could anyone tell me whats wrong? What am I doing wrong? I guess there is some way to compile only a module, not the whole kernel, which is very useful for developers. Does anyone know how to do so? Thanks, there comes my errors.... [root@localhost linux-2.4.20]# insmod net/bridge/bridge.o net/bridge/bridge.o: unresolved symbol __dev_get_by_name_Rsmp_dff2466c net/bridge/bridge.o: unresolved symbol register_netdev_Rsmp_807e44f8 net/bridge/bridge.o: unresolved symbol ether_setup_Rsmp_66797dc6 net/bridge/bridge.o: unresolved symbol eth_type_trans_Rsmp_697fcdb3 net/bridge/bridge.o: unresolved symbol netif_rx_Rsmp_c5346eca net/bridge/bridge.o: unresolved symbol __write_lock_failed net/bridge/bridge.o: unresolved symbol add_timer_Rsmp_a19eacf8 net/bridge/bridge.o: unresolved symbol del_timer_Rsmp_fc62f16d net/bridge/bridge.o: unresolved symbol __out_of_line_bug_Rsmp_8b0fd3c5 net/bridge/bridge.o: unresolved symbol dev_get_by_index_Rsmp_604eff36 net/bridge/bridge.o: unresolved symbol dev_set_promiscuity_Rsmp_c4ed559b net/bridge/bridge.o: unresolved symbol unregister_netdevice_notifier_Rsmp_fe769456 net/bridge/bridge.o: unresolved symbol __generic_copy_to_user_Rsmp_d523fdd3 net/bridge/bridge.o: unresolved symbol skb_over_panic_Rsmp_8f714d09 net/bridge/bridge.o: unresolved symbol skb_under_panic_Rsmp_26d771ad net/bridge/bridge.o: unresolved symbol br_ioctl_hook_Rsmp_1fb9705f net/bridge/bridge.o: unresolved symbol __br_write_unlock_Rsmp_702da97e net/bridge/bridge.o: unresolved symbol __read_lock_failed net/bridge/bridge.o: unresolved symbol __kfree_skb_Rsmp_fb8e515b net/bridge/bridge.o: unresolved symbol printk_Rsmp_1b7d4074 net/bridge/bridge.o: unresolved symbol kfree_Rsmp_037a0cba net/bridge/bridge.o: unresolved symbol unregister_netdev_Rsmp_091a1ac4 net/bridge/bridge.o: unresolved symbol kmalloc_Rsmp_93d4cfe6 net/bridge/bridge.o: unresolved symbol register_netdevice_notifier_Rsmp_63ecad53 net/bridge/bridge.o: unresolved symbol netdev_finish_unregister_Rsmp_d29730a1 net/bridge/bridge.o: unresolved symbol alloc_skb_Rsmp_6505afe0 net/bridge/bridge.o: unresolved symbol do_softirq_Rsmp_f0a529b7 net/bridge/bridge.o: unresolved symbol br_handle_frame_hook_Rsmp_aed5cfaa net/bridge/bridge.o: unresolved symbol irq_stat_Rsmp_ed7388c8 net/bridge/bridge.o: unresolved symbol dev_queue_xmit_Rsmp_38e4c261 net/bridge/bridge.o: unresolved symbol __br_write_lock_Rsmp_13836e40 net/bridge/bridge.o: unresolved symbol jiffies_Rsmp_0da02d67 net/bridge/bridge.o: unresolved symbol skb_clone_Rsmp_b0b1927a