Internetwork Routing 1

[HutchHutchison]

I am massively confused on internetworking communication ...

If computer A sends a packet to computer b, through a router...

what are the destnation IP address, destination mac and source IP and source mac.

I have looked from some answers, but I need some help.

And does this change if you add a second router into the equation?

 

[lerdalt]

This is kind of hard with out some graphics, but I hope I can help.

Quick layout:
[ComputerA]-------(router)--------[ComputerB]
ComputerA =
-ip address = 192.168.1.2/24
-MAC = 0000.0000.1111

Router interface Ethernet0 to ComputerA =
-ip address = 192.168.1.1/24
-MAC = 0000.0000.aaaa

ComputerB =
-ip address = 192.168.2.2/24
-MAC - 0000.0000.2222

Router interface Ethernet1 to ComputerB =
-ip address = 192.168.2.1/24
-MAC - 000.0000.bbbb

So computerA sends a packet to Computer B. The packet will be enter the router on interface Ethernet 0 with:
Source MAC = computerA
Source IP = computerA
Destination MAC = router
Destination IP = ComputerB

Packet will exit the router on interface Ethernet 1 with:
Source MAC = router
Source IP = computerA
Destination MAC = computerB
Destination IP = ComputerB

When the packet enters the router, it will strip off the layer2 addressing. As its exits the router it will add its own layer2 address.

Clear as mud?

 

[CiscoGuy33]

HutchHutchison,

In therory the packet and Layer 3 address (IP) stays the same from end to end - you will get to NAT and PAT soon enough and see where the private IP address is changed at the NAT router to a public address - this is the exception to the rule.

The layer 2 frame and its address is changed at each "hop" or router that it passes through. The layer 2 frame will reflect the layer 2 protocol that the router is using to communicate with the next router.[Layer2] (Layer3)

computer 1 - [Ethernet](IP) to router 1
router 1 - [Frame Relay](IP) to router 2
router 2 - [Ethernet](IP) to computer 2

I hope this clears some of the mud!!


E.A. Broda
CCNA, CCDA, CCAI, Network +

 

[HutchHutchison]

Thank you so much for your help!