IPaddress and Default gateway setting

[thangaRasu]

1. Does a router have a global ID / IP Address i.e A single IP which is used to  identify the router ?

2. Does Router have a default gateway for each I/F or is there a global  default gateway used for all interfaces

3. Router PPP link. Will those ports  also have a MAC ID or do only Ethernet ports have MAC IDs?

[devils_advocate]

1. It depends, if using OSPF the router will have a Router ID but in general the router will likely have several IP addresses.

2. The router itself doesn't have a default gateway as such because its job is to route packets using its routing table. It may have a default route however which is where to forward packets when there is no matching entry in the routing table. A switch or a host will have a default gateway so it knows where to forward frames which are not destinated for another host on its own Vlan.

3. Standard PPP doesn't use MAC addresses.

[thangaRasu]

Thank you for the response

I am not clear with the Answer 1 and 3( what is meant by Standard PPP)

[devils_advocate]

Well a routers job is to recieve packets on one interface, lookup the destination IP address in its routing table and then make a forwarding decision. Routers are Layer 3 devices so will have several IP addresses, effectively one for each L3 interface.

Picture a Router which has a LAN interface and a WAN interface. The WAN interface will likely have an external IP address and the LAN interface will have an internal private IP address. This is a very basic explanation but it illustrates my point that routers do not have a single 'global' IP address which is used to identify the router. In terms of the LAN, the router will have at least one private internal IP address which is used to remotely manage it via SSH/Telnet.

I was referring to Point to Point, in that it is its own protocol so doesn't use MAC addresses.