Routing protocol question

x5150

From the ciscopress book,

Which of the following are functions of a routing protocol?
d. To forward IP packets based on a packet's destination IP address.


Why is choice d. not correct here? Is it because 'routing protocol' is the process of learning/updating routes and the word 'routing' is reserved for the process of forwarding packets? Kind of confusing.


Next question,

Is it correct to say routers receive frames and forward packets (Then Layer 3 could be called frame receiving instead of packet forwarding)? In the ciscopress book pg 117 it uses the wording.

Router 1 processes the incoming frame, encapsulates the packet in an HDLC frame, and forwards the packet to Router 2. Router 2 processes the incoming frame, strips HDLC header, encapsulates the packet in a Frame Relay header and forwards the packet to Router 3. Router 3 processes incoming frame and forwards packet to PC2 (it also then says Router 3 encapsulates the packet in an Ethernet header and trailer with PC2s MAC, and forward the frame).

So they are using frame and packet interchangeably or what?

HDLC and Frame Relay are Data Link layer 2 protocols, and a Router is a Layer 3 device so it doesn't make sense in my head.

I'm just thinking the words frame, HDLC, Frame Relay goes with Layer 2 and packet, IP, routing with Layer 3.

xciton

Which of the following are functions of a routing protocol?
d. To forward IP packets based on a packet's destination IP address.

Why is choice d. not correct here?

Perhaps they are getting to the fact that the routing protocol does not do the forwarding of packets. RIP/EIGRP/OSPF populate the routing table, it's the actual router that forwards the packets along.

notgoing2fail

I really hate it when questions get this particular. I understand what they are trying to do, sometimes though it leaves to too much interpretation.

hexem

the hdlc/frame-relay are used to encpasulate layer3 packets to be sent to a remote device depending on the wan type being used, once it receives that frame it strips the frame off and re-encapsulates the packet within an ethernet frame to be sent to the PC, local area networks use ethernet so thing's change accordingly as packet's are sent through various networks.

remember differn't layer 2 encapsulation is needed to move upper layer information around.

remember the differnce between routing / routed

routing protocols = RIP, EIGRP, OSPF

routed protocols = IPV4, IPV6, IPX etc

xenodamus

The way I see it, router both recieve and forward frames...true. But to do their job (routing), they are more concerned with the destination of the packet inside the frame. They recieve a frame, strip the L2 header and trailer, examine the destination IP, rebuild the L2 header and trailer for the next link, and forward it on.

As far as routing protocols go, their job is not to forward packets (that definition would fit the router itself). Their job is to inform the router of routes/paths to other networks.

mikej412

notgoing2fail wrote: »

I really hate it when questions get this particular.

Routing/Routed is a basic concept you learn in the CCNA. It's not as high profile or glamorous as subnetting -- and unfortunately, unlike subnetting, it's one of those things someone can never "get" and still become a CCNA. String together enough of those "little things" and while they may become a CCNA, they just don't become a good CCNA.

The question is supposed to reinforce the concept of Routed vs Routing. If you missed that distinction in your studies, the question is your wake up call. That's the purpose of review questions -- to make sure you've learned the concepts the author deemed important.

Bl8ckr0uter

When I was studying I always thought of the Network as a neighborhood (full of houses and streets) Routing protocols as maps (of the streets and landmarks) and Routed Protocols as addresses on the houses on the map. It is a bit crude but I thought it worked out pretty well.

CiskHo

knwminus wrote: »

When I was studying I always though of the Network as a neighborhood (full of houses and streets) Routing protocols as maps (of the streets and landmarks) and Routed Protocols as addresses on the houses on the map. It is a bit crude but I thought it worked out pretty well.

Seems like a good analogy to me!

x5150

Thanks guys. I guess the way I'm going to try to remember it is,

routed protocol - packet information. ROUT-ED , PACK-ED.

routing protocol - ROUTer INformation