ARP command output

Let say i have to router A and B, both have S0 and E0. and the router connect each other through S0 and all the configuration is done. ping from to all the interface on the routers is successfull. if i telnet to router A and issues command "show arp", wat will be the result?

personally, i think mac add of the router B serial 0 interface.

please let me know if i am wrong...

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Comments

marlon23

Tricky question

serial interfaces do not have mac-addresses !!! , only ethernet one

you will see only MAC of RouterA if any.

brAun

em... i think serial interface should have mac address too....

any other people have any idea about this mac address and show arp command?

marlon23

Man, you dont know basics and you want to go for CCNA on monday?! (as you wrote in different topic)
I wish you a good luck, becouse I think you can only suceed with cheating.
And becouse you booked CCNA with knowledge you have, I am damn sure you are cheater.

And becouse you are so ignorant to people when they try to help you, I wouldn't waste my time to explain you why there is no such a thing as MAC address on serial interfaces.

EdTheLad

marlon23 wrote:

Man, you dont know basics and you want to go for CCNA on monday?! (as you wrote in different topic)
I wish you a good luck, becouse I think you can only suceed with cheating.
And becouse you booked CCNA with knowledge you have, I am damn sure you are cheater.

And becouse you are so ignorant to people when they try to help you, I wouldn't waste my time to explain you why there is no such a thing as MAC address on serial interfaces.

Another cat fight starts on techexams, why? no idea! i dont see any indication
of being ignorant, he only requested second opinions.Anyway back to the question, the serial interface by default will use hdlc encapsulation and since it forms a ptp link no address is required.There is an address field available in the hdlc header but its not used with cisco's implementation.

marlon23

when somebody has no idea about topic, and he wouldn't show no will to learn something, that is what I call to be ignorant. (still believes he has true, even with his poor knowledge, ignoring your clue. sorry, I have no patience with this-like persons.)

but ok, ed_the_lad is the dog here, so cats should clear the road

sprkymrk

marlon23 wrote:

when somebody has no idea about topic, and he wouldn't show no will to learn something, that is what I call to be ignorant. (still believes he has true, even with his poor knowledge, ignoring your clue. sorry, I have no patience with this-like persons.)

Hi marlon. I have to agree with Ed here. The guy was only asking for a second opinion, he wasn't trying to disrespect you. He wouldn't have asked the question if he wasn't willing to learn. If a guy doesn't know something, is he to assume that the first person who responds to his question does know? I have posted (in sincerety) wrong answers to topics on this forum before, and have been corrected - not flamed or called names. We are all learning from each other here, and your input is appreciated. Let's just give a guy the benefit of the doubt before we start slinging mud around.

By the way, I liked your comment about dogs and cats, never heard that before.

marlon23

I am grounded..

So sorry brAun, that I started this blame. But honestly, you need some study - you are missing basics. So dont be scared, and ask anything, we will help you to get your CCNA, and conquer CISCO!!!

brAun

i admit that i don't have very very strong knowledge in CCNA, but i have been studying for a long time.

i did the icnd exam half year ago and i got 825 which is nearly pass, after that i lose my interest in getting cert and didn't study until now. So i have book an exam to set a deadline for myself to push myself to study. i only review the material for 1 or 2 days only...

i should think of serial interface uses different data link layer protocol. but at least i got something from this.

marlon23, u really make me realise that i can't be like this anymore (being lazy). i must working harder to my ccna exam.

Danman32

You already passed ICND? Then all you need is intro and you certify.

Anyway, the point of a MAC is to identify a particular host on a multi-point network, such as Ethernet. With serial, there's only 2 points. Now frame relay can be multi-point, which is why there is a DLCI. The DLCI in this case is used in place of the MAC, and because of the way frame relay works, it uses Reverse Arp.

So for point-point serial, there is no hardware address other than the interface itself, therefore there is no ARP table for the serial interface. Consider also, that for Ethernet, the frame that goes across the ethernet interface includes the MAC destination and source address. The serial interface frame would not need or have physical addresses. It would simply place the IP packet on the wire, encapsulated by HDLC or PPP.

brAun

thanks danman32,
i have pass my intro last year Nov or this year jan. em.... i don't remember hehe... sry i got very bad memory. anyway i have done my intro.... so i am CCNA now. but i think i still need more study about routing and multilayer switching......but i willl do all this after i got my mcp.

lwwarner

Danman32 wrote:

The DLCI in this case is used in place of the MAC, and because of the way frame relay works, it uses Reverse Arp.

Frame relay uses Inverse ARP (InARP), not Reverse ARP (RARP), to map the local DLCI of a VC to the remote IP address. RARP, OTOH, is the obsolete predecessor of BOOTP/DHCP for self IP address discovery.

Danman32

I stand corrected. I do understand the method FR does IP/DLCI mapping though, I just got the term wrong.

skaeight

brAun, was this an actual practice question you found somewhere, or is it a hypothetical scenario you came up with?

Also, something that everyone else missed is that depending on where you are telneting into Router A from, the mac address from either the host you're telneting from, or the router between the host and Router A would be in the mac table.