Information Technology Reference
In-Depth Information
The Internet Control Message Protocol (ICMP) process on PC1 formulates a ping request to
PC3 and sends the reply to the IP process.
1.
The IP process on PC1 encapsulates the ping packet with a source IP address of
192.168.1.10
and destination IP address of
192.168.4.10
.
2.
PC1 then frames the packet with the source MAC address of (indicate device name)
PC1
and
the destination MAC address of (indicate device name)
R1
.
3.
Next, PC1 sends the frame out on the media as an encoded stream of
bits
.
4.
R1 receives the bit stream on its
FastEthernet 0/0
interface. Because the destination MAC
address matches the receiving interface's MAC address, R1 strips off the Ethernet header.
5.
R1 looks up the destination network address
192.168.4.0/24
in its routing table. This destina-
tion has a next-hop IP address of
192.168.2.2
. The next-hop IP address is reachable out inter-
face
Serial 0/0/0
.
6.
R1 encapsulates the packet in a High-Level Data Link Control (HDLC) frame and forwards the
frame out the correct interface. (Because this is a point-to-point link, no address is needed.
However, the address field in the HDLC packet contains the value 0x8F.)
7.
R2 receives the frame on the
Serial 0/0/0
interface. Because the frame is HDLC, R2 strips off
the header and looks up the network address
192.168.4.0/24
in its routing table. This destina-
tion has a next-hop IP address of
192.168.3.2
. The next-hop IP address is reachable out inter-
face
Serial 0/0/1
.
8.
R2 encapsulates the packet in an HDLC frame and forwards the frame out the correct interface.
9.
R3 receives the frame on the
Serial 0/0/1
interface. R3 strips off the header and looks up the
network address
192.168.4.0/24
in its routing table. This destination address is directly con-
nected to the
FastEthernet 0/0
interface.
10.
R3 encapsulates the ping request in a frame with the source MAC address of (indicated device
name)
R3
and the destination MAC address of (indicate device name)
PC3
.
11.
R3 then sends the frame out on the media as an encoded bit stream.
12.
PC3 receives the bit stream on its
Fast Ethernet
interface. Because the destination MAC address
matches the MAC address of PC3, PC3 strips off the Ethernet header.
13.
The IP process on PC3 examines the
192.168.4.10
IP address to make sure that it matches its
own IP address. Then PC3 passes the data to the ICMP process.
14.
The ICMP process on PC3 formulates a ping reply to PC1 and sends the reply to the IP
process.
15.
The IP process on PC3 encapsulates the ping packet with a source IP address of
192.168.4.10
and destination IP address of
192.168.1.10
.
16.
PC3 then frames the packet with the source MAC address of (indicate device name)
PC3
and
the destination MAC address of (indicate device name)
R3
.
17.
PC3 then sends the frame out on the media as an encoded bit stream.
18.
R3 receives the bit stream on its
FastEthernet 0/0
interface. Because the destination MAC
address matches the receiving interface's MAC address, R3 strips off the Ethernet header.
19.
R3 looks up the destination network address
192.168.1.0/24
in its routing table. This destination
has a next-hop IP address of
192.168.3.1
. The next-hop IP address is reachable out interface
Serial 0/0/1
.
20.
