Use the ifconfig –a output to calculate the new collisions seen at the interfaces of PC1 and PC3. Explain the differences between the outcomes in Exercise 3(A) and Exercise 3(B).

What will be an ideal response?

Before: PC1
```
eth0 Link encap:Ethernet HWaddr 00:50:BF:90:7D:33
inet addr:10.0.1.11 Bcast:10.0.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:533854 errors:0 dropped:0 overruns:0 frame:0
TX packets:539437 errors:0 dropped:0 overruns:0 carrier:0
collisions:2173 txqueuelen:100
RX bytes:52175980 (49.7 Mb) TX bytes:59977807 (57.1 Mb)
Interrupt:9 Base address:0x6c00
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:79957 errors:0 dropped:0 overruns:0 frame:0
TX packets:79957 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:5449922 (5.1 Mb) TX bytes:5449922 (5.1 Mb)
After:
eth0 Link encap:Ethernet HWaddr 00:50:BF:90:7D:33
inet addr:10.0.1.11 Bcast:10.0.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:958765 errors:0 dropped:0 overruns:0 frame:0
TX packets:964348 errors:0 dropped:0 overruns:0 carrier:0
collisions:2173 txqueuelen:100
RX bytes:93817144 (89.4 Mb) TX bytes:101618971 (96.9 Mb)
Interrupt:9 Base address:0x6c00
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:79957 errors:0 dropped:0 overruns:0 frame:0
TX packets:79957 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:5449922 (5.1 Mb) TX bytes:5449922 (5.1 Mb)
```
Before: PC3
```
eth0 Link encap:Ethernet HWaddr 00:50:BF:90:67:74
inet addr:10.0.1.31 Bcast:10.0.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:500 Metric:1
RX packets:1010957 errors:0 dropped:0 overruns:0 frame:0
TX packets:2547 errors:0 dropped:0 overruns:0 carrier:0
collisions:10 txqueuelen:100
RX bytes:99072344 (94.4 Mb) TX bytes:225038 (219.7 Kb)
Interrupt:9 Base address:0x6c00
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:114498 errors:0 dropped:0 overruns:0 frame:0
TX packets:114498 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:7371986 (7.0 Mb) TX bytes:7371986 (7.0 Mb)
After:
eth0 Link encap:Ethernet HWaddr 00:50:BF:90:67:74
inet addr:10.0.1.31 Bcast:10.0.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:500 Metric:1
RX packets:1011076 errors:0 dropped:0 overruns:0 frame:0
TX packets:2649 errors:0 dropped:0 overruns:0 carrier:0
collisions:10 txqueuelen:100
RX bytes:99083322 (94.4 Mb) TX bytes:234958 (229.4 Kb)
Interrupt:9 Base address:0x6c00
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:114498 errors:0 dropped:0 overruns:0 frame:0
TX packets:114498 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:7371986 (7.0 Mb) TX bytes:7371986 (7.0 Mb)
```
After adding a bridge (Router1) between the two hubs and again running the ping commands as in Exercise 3B, no more messages were lost due to collisions after the introduction of the bridge. From the bridge table output we note that messages from PC1 meant for PC2 and from PC2 to PC1 are not forwarded by the bridge to the hub for hosts PC3 and PC4, and vice versa. Hence there are no more collisions.