Add second year

second/semester2/CT2108/Labs/Lab-01/Lab1.md

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+#1 hex vals of source & destination MA addresses in ethernet frame containing arp request messages
+Sender MAC address: IntelCor_4b:81:47 (20:1e:88:4b:81:47)
+Sender MAC address: IntelCor_4b:81:47 (20:1e:88:4b:81:47) 
+
+# 2hex val two byte ether frane type in arp request messages
+packet type: sent by us (4) 
+Port numbers are the way the TRANSPORT layer recognizes which packet belongs to what process at the end systems.
+They're used to let the process-to-process delivery work; but ICMP, from a functional point of view, is not a transport layer protocol.
+
+ICMP is a messaging protocol at the Network layer(on top of the IP; but not really in the transport layer), it's got a lot of responsibilities but none of them has anything to do with process-to-process delivery, so having a port number there wouldn't make any sense.
+
+# 3ip addr of host and ip addr of dest host for ping. why icmp not have source n destination 
+Source Address: 140.203.135.95
+Destination Address: 104.18.143.17
+
+#4 icmp type n code nums of ping reqs sent by host. what other fields does this icmp pack have. no bytes checkusum seq num identify fields
+

second/semester2/CT2108/Labs/Lab-01/instructions.md

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+- To get network interface information use: `ip address`. 
+- To view the ARP cache: `ip neigh`. 
+- To delete the ARP cache: `ip -s neigh flush all`. 
+- To run a ping with a large payload and not allow IP fragmentation: `ping -M do -s 1600 www.rte.ie`. 
+- To display the routing table on your device: `ip route`. 
+- To run a traceroute without DNS name lookoup: `traceroute -n www.rte.ie`.