Simmi Singla wrote: > > Hi all, > Can anybody explain me when i use the broadcast keyword in sub > interface(fram-relay interface-dlci 16 broadcast) then if i > have only static routing will it affect that.I read that it is > used only for OSPF to pass broadcasts , if multicasting > disabled.But In a scenario if I have no dynamic routing and > give this command what will happen. > will it pass unknown broadcasts on frame-relay.
Remember a router doesn't pass broadcasts, i.e. forward broadcasts. So think about when you would need to let a router send broadcasts on its own, from its own interface. The usual case is to support dynamic routing. If you are using static routing, then you don't have to worry about it. Frame Relay is used on routers to create virtual circuits to remote sites. A point-to-point virtual circuit can send broadcasts without any problem. Frame Relay is often designed in a hub-and-spoke topology, however, with the hub router connecting many remote sites. A typical design is to place all the WAN serial interfaces in this design in the same subnet, thus creating a multiaccess WAN "cloud." The cloud resembles a LAN subnet, but does not support broadcasting like a LAN would. The cloud is a nonbroadcast multiaccess (NBMA) network. When a router sends a broadcast into the cloud, only a directly connected router on the same virtual circuit hears it. Many protocols were designed with the assumption that two hosts on the same subnet have Layer 2 connectivity and can easily hear each other's broadcasts. This isn't the case in a Frame Relay hub-and-spoke topology. So to fix the problem, if this is your design, you better add the "broadcast" keyword if you are using dynamic addressing. For example, use seomthing like "frame-relay map protocol address broadcast." The other solution, however, is to use subinterfaces. This turns the links back into normal point-to-point links. Then they support broadcast no problem. Chuck can correct me if I got this wrong! :-) Priscilla > moreover exactly how it is used in point-to-point sub > interfaces. > Thanx a lot in advance--:) Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=61865&t=61829 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
