MAC Address Questions
triplebenc
Member Posts: 28 ■□□□□□□□□□
in CCNA & CCENT
Hey guys, I was wondering if you could help me out w/ this:
Switch2
PC3
|
|
Router
|
|
|
Switch1
PC2
|
|
PC1
Couple things that I dont get are:
If pc 1 sends a packet to pc2, then what will be pc1's destination MAC?
When pc 2 recives this packet, doest it see Switch one's MAC or PC1 Mac?
If PC1 sends a packet to PC3 through a router, is the destination MAC the router, or is is pc3? and does pc3 see switch 2's MAC or the routers Mac?
Probably kind of confusing, but these are some questions I ran into taking a test and wasnt sure about them. Pretty much what pc's see when a packet is sent. I know that the IP addresse's never change, but just not sure about the MAC address. Thanks a bunch guys! I just took the test and got an 800 so I'm almost there!
Switch2
PC3
|
|
Router
|
|
|
Switch1
PC2
|
|
PC1
Couple things that I dont get are:
If pc 1 sends a packet to pc2, then what will be pc1's destination MAC?
When pc 2 recives this packet, doest it see Switch one's MAC or PC1 Mac?
If PC1 sends a packet to PC3 through a router, is the destination MAC the router, or is is pc3? and does pc3 see switch 2's MAC or the routers Mac?
Probably kind of confusing, but these are some questions I ran into taking a test and wasnt sure about them. Pretty much what pc's see when a packet is sent. I know that the IP addresse's never change, but just not sure about the MAC address. Thanks a bunch guys! I just took the test and got an 800 so I'm almost there!
Comments
-
Ahriakin
Member Posts: 1,799 ■■■■■■■■□□
The switch bridge ports/interfaces have no mac address of their own. So PC1 sets PC2's Mac as the destination address.
In the second case PC1 knows Router3 is it's Default Gateway and uses PC3's IP address BUT the router's Mac address (The router then uses PC3's mac address out the other side). PC3 sees the Router's MAC as the source of the frame, but PC1 as the Source IP - since return messages are routed by IP and not MAC this is not a problem.
The basic rule of thumb is this: When passing through Layer2 devices (Switches/Bridges) the Mac address remains that of the target. When you have to pass through a Layer3 device (Router) the Mac address is that of the Device and not the target.We responded to the Year 2000 issue with "Y2K" solutions...isn't this the kind of thinking that got us into trouble in the first place?