# Rabbit Board 4000 **URL:** \ **Category:** Rabbit Software\ **Tags:** dynamicc, rabbit-4000\ **Created:** [July 23, 2015, 5:44pm UTC](https://forums.digi.com/t/rabbit-board-4000/15165 "2015-07-23T17:44:58Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![wse-ltd.com](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@wse-ltd.com](https://forums.digi.com/u/wse-ltd.com)\ **Post date:** [July 23, 2015, 5:44pm UTC](https://forums.digi.com/t/rabbit-board-4000/15165/1 "2015-07-23T17:44:58Z")
hello, I have a rabbit board 4000 BL4S160 2m serial program flash. Basically after I power cycle the network router which connects to the board (simulating an extended power outage), the values stored in memory are lost. I have replaced the battery to no avail. I have inherited this code and controller so I am kind of new to does? Any ideas on where to start? ---
**Author:** ![petermcs](https://avatars.discourse-cdn.com/v4/letter/p/4af34b/32.png) [@petermcs](https://forums.digi.com/u/petermcs)\ **Post date:** [July 24, 2015, 12:13am UTC](https://forums.digi.com/t/rabbit-board-4000/15165/2 "2015-07-24T00:13:05Z")
I have seen something similar in my products where the Rabbit device is set to use Link Local addressing in the absence of a DHCP server. What happens is that when the router goes down, the rabbit board changes network and then when the router is restored it changes network again. There is a bug in the TCP/IP stack which as far as I can remember, relates to how the stack stores its list of routers which can end up in a loop writing to memory beyond the end of the list. I modified the code to always clear the list of routers in this case and it solved the problem for me - I did report the issue to Digi but I don’t think they tried to get to the bottom of it. I’m working on adding support for a GPRS module to my product and will have to revisit this whole area as the simple fix I put in place does not work if you have more than one network connection as every time the GPRS connection is dropped, all the routers are flushed. Regards, Peter ---
**Author:** ![wse-ltd.com](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@wse-ltd.com](https://forums.digi.com/u/wse-ltd.com)\ **Post date:** [July 26, 2015, 5:46pm UTC](https://forums.digi.com/t/rabbit-board-4000/15165/3 "2015-07-26T17:46:59Z")
OK thanks Peter. Here is my code snippet for the network handler: ```auto //IP network handler thread while(1) { if(ifpending(IF_DEFAULT) != IF_UP)//if nextwork interface isn't up... { // Start network and wait for interface to come up. do { sock_init();//initialist TCP socket for HTTP Post commands. ifdown(IF_ETH0); while (ifpending(IF_ETH0) == IF_COMING_DOWN) { tcp_tick(NULL); yield; } ifconfig(IF_ETH0, IFS_DOWN, IFS_IPADDR, aton(IPAddressString), IFS_NETMASK, aton(SubnetString), IFS_ROUTER_SET, aton(DefaultGatewayString), IFS_NAMESERVER_SET, aton(DNSServerString), IFS_UP, IFS_END); yield; while (ifpending(IF_DEFAULT) == IF_COMING_UP) { tcp_tick(NULL); yield; } }while(ifpending(IF_DEFAULT) != IF_UP); //Network must be up so initialise http server, and reserve port 80 for multiple web connections http_init(); tcp_reserveport(80); printf("set up network "); printf(" done"); } //run the http server daemon and process TCP services http_handler(); tcp_tick(NULL); yield; } ``` Could you provide a code snippet to clear the list of routers please? -Paramjit ---
**Author:** ![wse-ltd.com](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@wse-ltd.com](https://forums.digi.com/u/wse-ltd.com)\ **Post date:** [July 26, 2015, 5:47pm UTC](https://forums.digi.com/t/rabbit-board-4000/15165/4 "2015-07-26T17:47:54Z")
OK thanks Peter. Here is my code snippet for the network handler: //IP network handler thread while(1) { if(ifpending(IF\_DEFAULT) != IF\_UP)//if nextwork interface isn’t up… { // Start network and wait for interface to come up. do { sock\_init();//initialist TCP socket for HTTP Post commands. ifdown(IF\_ETH0); while (ifpending(IF\_ETH0) == IF\_COMING\_DOWN) { tcp\_tick(NULL); yield; } ifconfig(IF\_ETH0, IFS\_DOWN, IFS\_IPADDR, aton(IPAddressString), IFS\_NETMASK, aton(SubnetString), IFS\_ROUTER\_SET, aton(DefaultGatewayString), IFS\_NAMESERVER\_SET, aton(DNSServerString), IFS\_UP, IFS\_END); ``` yield; while (ifpending(IF_DEFAULT) == IF_COMING_UP) { tcp_tick(NULL); yield; } }while(ifpending(IF_DEFAULT) != IF_UP); //Network must be up so initialise http server, and reserve port 80 for multiple web connections http_init(); tcp_reserveport(80); printf("set up network ``` “); printf(” done"); ``` } //run the http server daemon and process TCP services http_handler(); tcp_tick(NULL); yield; } ``` Could you provide a code snippet to clear the list of routers please? -Paramjit WSE Ltd ---
**Author:** ![petermcs](https://avatars.discourse-cdn.com/v4/letter/p/4af34b/32.png) [@petermcs](https://forums.digi.com/u/petermcs)\ **Post date:** [July 27, 2015, 1:41am UTC](https://forums.digi.com/t/rabbit-board-4000/15165/5 "2015-07-27T01:41:33Z")
I fixed the problem in my case by changing the router\_del\_all() function in ARP.lib to the following: // PMCS \_arp\_nodebug void router\_del\_all(void) { auto unsigned i; auto RTEntry \* rte; auto ATHandle ath; auto ATEntry \* ate; ``` // This function may be called pre-sock_init(). If so, then there will // be no ARP cache entries, so flush will not be called. ``` LOCK\_GLOBAL\_IF\_INIT(TCPGlobalLock); #ifndef ARP\_MINIMAL #ifdef ARP\_VERBOSE printf("ARP: deleting all routers "); #endif for (i = 0, rte = \_arp\_gate\_data; i \< ARP\_ROUTER\_TABLE\_SIZE; ++i, ++rte) if (rte-\>ath) { ath = ATH2INDEX(rte-\>ath); if (ath \< ARP\_TABLE\_SIZE) { ate = \_arp\_data + ATH2INDEX(ath); ate-\>flags &= ~ATE\_ROUTER\_ENT; // No router any more ate-\>ath = 0; \_arp\_unlink\_to(ate); } ``` rte->ath = 0; } ``` #else memset(\_arp\_gate\_data, 0, sizeof(\_arp\_gate\_data)); #endif UNLOCK\_GLOBAL\_IF\_INIT(TCPGlobalLock); } This solved the crashing problem but will only work for boards with a single network interface. I’m going to have to figure out something better soon as I want to have a GPRS interface in addition to the Ethernet one. ---
**Author:** ![wse-ltd.com](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@wse-ltd.com](https://forums.digi.com/u/wse-ltd.com)\ **Post date:** [July 28, 2015, 8:39am UTC](https://forums.digi.com/t/rabbit-board-4000/15165/6 "2015-07-28T08:39:14Z")
I am trying this today and will let you know how it goes. Thanks. ---
**Author:** ![wse-ltd.com](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@wse-ltd.com](https://forums.digi.com/u/wse-ltd.com)\ **Post date:** [August 3, 2015, 11:02am UTC](https://forums.digi.com/t/rabbit-board-4000/15165/7 "2015-08-03T11:02:45Z")
looks like the main problem was the battery on the board needed replacing. It is now able to retain memory values after long power outage. thanks for the help.