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Dear friends ,

Kindly give me authoritative answers to my following queries , since I am writing CCNA EXAM shortly:

1.When a download of frames/files takes place from a remote server on one's host PC then Frames landing at the host PC shall have WHOSE SOURCE MAC ADDRESS - THAT OF THE NEAREST ROUTER TO THE HOST PC OR THAT OF THE SENDER SERVER ?

2.A ROUTER AND A SWITCH ARE CONNECTED VIA FASTETHERNET PORTS - WHICH TYPE OF CABLING MUST BE USED - CROOSSOVER OR STRAIGHTTHROUGH (both fao ports use RJ 45 Connectors which means the same connecting devices on both ends- this creates confusion- if I am writing CCNA exam which option must I choose - CROSSOVER or STRAIGHTTHROUGH CABLE?)

3.A newly purchased router has old NVRAM in it , what must be done with this NAVRAM - SAVED OR ERASED ?

4.ARP really belongs to which OSI layer - Network or Datalink?

5.Are following correctly matched:


NNTP - 119 (UDP)

6.What is the correct sequence to configure dial-on-demand routing on an ISDN BRI interface? it true that TE2 is a serial interface on a router? iF YES OR NO , REASONS FOR THE SAME.

8.Data field in a frame consists of 46-1500 bytes or 64-1500 bytes?

9.What is the basic function of frame-relay DLCI - is it identification of circuit between the local router and the nearest connecting Frame-Switch or the is it the identification of circuit between the far end router and the Frame-Switch?

9.Does multicasting not cause congestion?

10.Is it true that TRUNK PORTS are not configured on routers and that these are done so on switches only?

11.what is the maximum number of loopback interfaces that a router can have?

An early response shall highly be appreciated!

With Warm Regards

Lovely Person


1. The MAC address of the router is used.

2. Straight-through.

3. Erased.

4. Datalink.

9. Identification between the local router and the connected frame relay switch.

9. Multicasting can cause congestion if there is more packets sent than the capacity of the network, same as any other type traffic. However, multicasting will cause less congestion than sending the same packet individually several times as a unicast.

10. Trunk ports may be configured on routers in "router-on-a-stick" scenarios. Configure sub-interfaces on the fast/gigabit-ethernet interface with encapsulation of "isl (vlan#)" or "dot1q (vlan#)".

11. I have never run across a limit of loopback interfaces, but as with any software product, there must be some limit.

I've got to go. I will answer the rest of your questions when I get back.


Hi Lovely,

Your answers are as below

1) Source address will be on the nearest Router which is doing the routing.

2) You need straigh through cable between router and switch as they belong to different group

3) A new purchased router will have NVRAM with default config. So you can sinply start configuring what you want your router to do. Incase it is a second hand router which you purchased you want you can delete the old conig and start with all new config as per your requirement.

4) ARP belongs to OSI data link layer (layer 2)

Check this link for all the details on ARP

5) NTP uses UDP port 123

NNTP uses both TCP and UDP on 119

6) Config should something like this

interface BRI0

no ip address

encapsulation ppp

dialer pool-member 1

isdn switch-type ntt

ppp authentication chap


interface Dialer1

ip address x.x.x.x x.x.x.x

encapsulation ppp

dialer map ip x.x.x.x name ABC

dialer load-threshold 120 either

dialer pool 1

dialer-group 1

ppp authentication chap

ppp multilink

dialer-list 1 protocol ip list 101

ip access-list 101 permit -------->traffic what you want to permit

7) Yes it is a serial interface

8) Data field in a frame consists of 46-1500 bytes

9) Frame Relay virtual circuits are identified by data-link connection identifiers (DLCIs). DLCI values typically are assigned by the Frame Relay service provider (for example, the telephone company).

Frame Relay DLCIs have local significance, which means that their values are unique in the LAN, but not necessarily in the Frame Relay WAN. It is it identification of circuit between the local router and the nearest connecting Frame-Switch

10) Trunk ports are basically configured on the switches but if you want intervlan routing i.e routing between the vlans then you will configure trunk on switch and you will cofigure sub interfaces on router and configure them with dot1q encapsulation so it will also work as a trunk port where all the vlans trffic will be passed from switch to the router. So router can support encapsulation for intervlan routing. But basic functionality of trunk ports are between the switches only.

11) There is high limit of loop back interfaces which you can configure on routers

eg: 7200 VXR can support <0-2147483647>

6500 sup2 msfc 2 also support <0-2147483647>

2500 router also support same number