[lwip-users] lwip network interface

[bhavani sai prasad]

Hi every one,
              I have a doubt regarding network interface in lwIP.My question is in network interface structure.

struct netif {
struct netif *next;
char name[2];
int num;
struct ip_addr ip_addr;
struct ip_addr netmask;
struct ip_addr gw;
void (* input)(struct pbuf *p, struct netif *inp);
int (* output)(struct netif *netif, struct pbuf *p,
struct ip_addr *ipaddr);
void *state;
};

1.How is "gw" field used to search network interface while sending and recving data?
2.what is the use of "gw"? Is this "gw" field used only for default network interface or for all the interfaces?
3.what is default interface?will it be like "netif" structure (or) "gw" field is called as default network interface.
4.let us say if my system have 3 interfaces.one interface eth interface ,second one as token ring interface and third one as default interface.
is it possible to have an interface like this?

please give me breafe idea about this concept.

thankx in advance.

rgds,
chinna