Am I correct

Hello again, just want to clear things out

I have PC1

router1

router2

PC2

Scenario: PC1 want to send data to pc2 so
the Source ip = pc1 and Destination IP = pc 2
On the frame the source mac is pc1 and destination mac is pc2
the default gateway of pc1 is router1 ethernet interface.

In the router1 the frame is discarded and the source ip and destinaion ip in the packet will remain and the destination ip network will be checked.

Since r1 knows how to get to the n2 by going to r2 it will send it to it's exit interface.

here the Source ip = pc1 and destination ip is pc2 but the MAC source address is router 1 serial interface and the destination mac is router 2 serial interface.

Please do not explain the arp, just tell me if I am correct I forgot since I am finished reading my Sybex and the CBT video and I don't want to re-read again or watch.

Thanks for the help.

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Comments

ciscos

i think its ok.
never mind...it seems you have understand the gist which is
that ip's remain the same and only tha mac's are changing.

chinaman

Thanks for the big help

dmaftei

On the frame the source mac is pc1 and destination mac is pc2

The destination MAC is router1's ethernet.

... but the MAC source address is router 1 serial interface and the destination mac is router 2 serial interface.

There's no MAC address on serial interfaces.

chinaman

oh sorry I forgot there's no mac on r1 to r2 bec it is a L3.

Can you tell me the
SIP
DIP
MACS
DESSource

in R1 to R2

Thanks

EdTheLad

chinaman wrote:

oh sorry I forgot there's no mac on r1 to r2 bec it is a L3.

Can you tell me the
SIP
DIP
MACS
DESSource

in R1 to R2

Thanks

It depends on what encapsulation is configured on your serial interface.By default it is hdlc,this means the inital ethernet frame entering the router will be unencapsulated and the ip packet will be encapsulated within a hdlc frame.The cisco hdlc frame doesnt actively use an address and as its a ptp link you can just view the ip being transported accross the serial link transarently.The same idea goes if you are using PPP.If you use frame relay the data will be encapsulated into a FR frame and a DLCI will be used for addressing.

chinaman

thanks

chinaman wrote:

Hello again, just want to clear things out
I have PC1
to
router1
to
router2
PC2

chinaman wrote:

On the frame the source mac is pc1 and destination mac is pc2

I have a slight doubt:

When the frame leaves PC1 will the destination MAC address be of PC2 or router1.

EdTheLad

It will use the default gateways MAC address which in this case is R1.

dublin_101

stick to the principals..........

the source and destination I.P Addresses always remain the same!

however

the mac addresses will change from router to router..............remember routers operate on layer 3, but, the wan protocols are layer 2, and therefore it needs the mac address!!