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ip_print_ifs returns wrong MTU.

0 votes
ip_print_ifs(); returns a MTU of 16 yet it is defined as 1500.

ifmtu(i, 0)); returns goofy values but ifmtu(i, _if_tab[0].ipaddr)); returns 1500.

in ip.lib

printf("%-4s %4u ", IF_P2P(i) ? (IF_PKT_ETH(i) ? "ppoe" : "ppp") : IF_PKT_REAL_WIFI(i) ? "wifi"
: "eth", ifmtu(i, _if_tab.ipaddr));

Returns 16

Something is very goofy.
asked Sep 12, 2014 in Rabbit by dbt3481 New to the Community (0 points)

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3 Answers

0 votes
You didn't give any relevant information. What version of DC are you using? What Rabbit board are you using?

What networking parameters do you have set up? How did you set them up?
answered Sep 12, 2014 by trooper2 Veteran of the Digi Community (591 points)
DC 10.72 and a RCM4310

#define TCPCONFIG 1  /* Static IP */
#define _PRIMARY_STATIC_IP  ""
#define _PRIMARY_NETMASK    ""
#define MY_GATEWAY          ""
#define MY_NAMESERVER       ""

   GetIpAddress(IpAddress); //This reads the IP from a set of 8 hex rotary switches...

              IFS_IPADDR, aton(IpAddress),
            IFS_NETMASK, aton(""),
    while (ifpending(IF_ETH0) == 1) tcp_tick(NULL);

0 votes
In DC 10.72 Function lookup:
ip_print_ifs <IP.LIB>

SYNTAX: void ip_print_ifs(void)

KEYWORDS: tcpip, interface

DESCRIPTION: Print all interface table entries. This is for debugging
only, since the results are printed to the Dynamic C stdio

There are 8 fields for each interface entry:
the interface number
IP addr:
The local ("home") IP address of this interface. May
be if interface is not currently active.
Local subnet mask.
Indicates status; one of
Yes: interface currently active
No: currently inactive
NYU: Not Yet Up i.e. coming up
NYD: Not Yet Down i.e. coming down
Interface type; one of
eth: normal ethernet
ppp: PPP over serial port
pppoe: PPP over ethernet
Maximum transmission unit.
A list of the following characters:
* = this is the default interface (IF_DEFAULT)
D = Use DHCP
DD= Currently configured via DHCP
S = allow IP address configuration via directed
ping (ICMP echo).
SS= IP address currently set via directed ping
1 = IGMP version 1 router present on this interface
->nn = Virtual interface on specified real i/f
IP address of peer node (for PPP or PPPOE), or address
of default router on this interface (for ethernet
type). May be blank or if no peer or router
is available.
answered Sep 12, 2014 by MargaretK Veteran of the Digi Community (545 points)
0 votes
When I run display_mac.c on an RCM4310 I get

# IP addr. Mask Up Lnk Type MTU Flags Peer/router

--- --- ---- ----

0 yes yes eth 16 *

When I run it on an RCM6750 I get

# IP addr. Mask Up Lnk Type MTU Flags Peer/router

--- --- ---- ----

0 yes yes eth 1500 *

I would assume this is a bug as the MTU should be 1500 for ethernet and 1489 if WiFi and Rabbit 5000 or above.
answered Sep 15, 2014 by trooper2 Veteran of the Digi Community (591 points)
Indeed, I looked into debugging it but gave up as I have more pressing issues.