10-01-2016 02:05 PM - edited 03-05-2019 07:10 AM
So there is this simple GNS3 topology. The host is Ubuntu Linux tap0 interface.
ifconfig output:
tap0 Link encap:Ethernet HWaddr fe:6b:25:17:ab:af
inet addr:192.168.2.2 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::fc6b:25ff:fe17:abaf/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:995 errors:0 dropped:805 overruns:0 frame:0
TX packets:69 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:98098 (98.0 KB) TX bytes:9562 (9.5 KB)
R1# show ip route:
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, FastEthernet0/0
C 192.168.2.0/24 is directly connected, FastEthernet0/1
R2# show ip route:
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, FastEthernet0/0
R 192.168.2.0/24 [120/1] via 10.0.0.1, 00:00:04, FastEthernet0/0
When I ping from Host to R1 ( or R1 to Host ) its fine.
When I ping from R2 to R1 ( or R1 to R2 ) its fine.
When I ping from R2 to Host ( or Host to R2 ) all packets are lost.
The routing seems fine what is the problem here ?
10-01-2016 08:23 PM
What is the gateway set to on the Linux host? Should be able to see that with a "route -n". R2 knows how to reach the 192.168.2.0/24 subnet so it should be able to reach the host. I see a lot of drops on your tap0 interface. You can run an "ethtool -S tap0" and that should show you why the host is dropping the packets (possible duplex / speed mismatch?).
10-03-2016 09:37 AM
Ooutput of ethtool -S tap0:
no stats available
Output of route -n:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 146.176.231.254 0.0.0.0 UG 600 0 0 wlan2
1.1.1.1 146.176.231.254 255.255.255.255 UGH 600 0 0 wlan2
146.176.224.0 0.0.0.0 255.255.248.0 U 600 0 0 wlan2
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 wlan2
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 tap0
10-03-2016 04:06 PM
Ah yea, there's your issue. The default route on your server is pointing out of wlan2 and you don't have a route for the 10.0.0.0/24 network. This means that right now traffic destined to the 10.0.0.0/24 is being sent out your wlan2 interface rather than your tap0 interface.
On the server, create a static route for the 10.0.0.0/24 to route out your tap0 interface and your pings should be successful after that.
10-10-2016 12:25 PM
I just did the whole thing in Windows. Thanks for the info though.
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