Gateway Config

gateway_ip_NOT_specified.md

Gateway IP (192.168.10.1) is NOT specified

Host 1

root@host1:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.0.2.2        0.0.0.0         UG    0      0        0 eth0
10.0.2.0        *               255.255.255.0   U     0      0        0 eth0
192.168.10.0    *               255.255.255.0   U     0      0        0 eth1
192.168.20.0    *               255.255.255.0   U     0      0        0 eth1

root@host1:~# ping 192.168.20.20
PING 192.168.20.20 (192.168.20.20) 56(84) bytes of data.
From 192.168.10.10 icmp_seq=1 Destination Host Unreachable
From 192.168.10.10 icmp_seq=2 Destination Host Unreachable
From 192.168.10.10 icmp_seq=3 Destination Host Unreachable
From 192.168.10.10 icmp_seq=4 Destination Host Unreachable
From 192.168.10.10 icmp_seq=5 Destination Host Unreachable
From 192.168.10.10 icmp_seq=6 Destination Host Unreachable
^C
--- 192.168.20.20 ping statistics ---
7 packets transmitted, 0 received, +6 errors, 100% packet loss, time 6019ms
pipe 3

Host 2

NOTE: tcpdump started before ping was issued in host 1

root@host2:~# tcpdump -n -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
22:46:45.338178 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:46.337945 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:47.338237 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:48.341552 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:49.337374 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:50.338895 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:51.356868 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:52.357944 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46
22:46:53.358751 ARP, Request who-has 192.168.20.20 tell 192.168.10.10, length 46

gateway_ip_specified.md

Gateway IP (192.168.10.1) is specified

Host 1

root@host1:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.0.2.2        0.0.0.0         UG    0      0        0 eth0
10.0.2.0        *               255.255.255.0   U     0      0        0 eth0
192.168.10.0    *               255.255.255.0   U     0      0        0 eth1
192.168.20.0    192.168.10.1    255.255.255.0   UG    0      0        0 eth1

root@host1:~# ping 192.168.20.20
PING 192.168.20.20 (192.168.20.20) 56(84) bytes of data.
^C
--- 192.168.20.20 ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5026ms

Host 2

NOTE: tcpdump started before ping was issued in host 1

root@host2:~# tcpdump -n -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
22:40:42.297004 IP 192.168.10.10 > 192.168.20.20: ICMP echo request, id 3372, seq 1, length 64
22:40:43.305269 IP 192.168.10.10 > 192.168.20.20: ICMP echo request, id 3372, seq 2, length 64
22:40:44.313704 IP 192.168.10.10 > 192.168.20.20: ICMP echo request, id 3372, seq 3, length 64
22:40:45.322191 IP 192.168.10.10 > 192.168.20.20: ICMP echo request, id 3372, seq 4, length 64
22:40:46.322609 IP 192.168.10.10 > 192.168.20.20: ICMP echo request, id 3372, seq 5, length 64
22:40:47.306915 ARP, Request who-has 192.168.10.1 tell 192.168.10.10, length 46
22:40:47.306963 ARP, Reply 192.168.10.1 is-at 08:00:27:be:b2:2f, length 28
22:40:47.322725 IP 192.168.10.10 > 192.168.20.20: ICMP echo request, id 3372, seq 6, length 64