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I have an issue with the internet connection in Ubuntu not working any longer.

I have two NIC's. Both static. One with a internet IP and one local. I can SSH into local fine, but the internet IP cannot be seen outside the network. I have 5 static internet IP's (only 1 assigned to this server) and the others work fine with the same configurations, so I know it's not the ISP. I can also ping the other internet IPs I have, but I can't ping out - say to google's 8.8.8.8.

netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
XX.49.84.232   0.0.0.0         255.255.255.248 U         0 0          0 eth1
172.24.98.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
0.0.0.0         XX.49.84.238   0.0.0.0         UG        0 0          0 eth1

/etc/network/interfaces file:
auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet static
address 172.24.98.60
netmask 255.255.255.0

auto eth1
allow-hotplug eth1
iface eth1 inet static
address XX.49.84.237
gateway XX.49.84.238
netmask 255.255.255.248

Any ideas? Thank you so much!

KIT
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1 Answers1

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Check route to 8.8.8.8:

$ ip ro get 8.8.8.8
8.8.8.8 via XX.49.84.238 dev eth0  src XX.49.84.237 
    cache  mtu 1500 advmss 1460 hoplimit 64

Then run tcpdump and ping 8.8.8.8:

# tcpdump -pni eth1                  (one console)
# ping 8.8.8.8                       (second console)

Copy output in question.

Also check ARP:

$ arp -a
XX.49.84.238 (XX.49.84.238) в xx:xx:xx:xx:xx:xx [ether] на eth1

And iptables rules:

# iptables -nv -L
ooshro
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  • ip ro get 8.8.8.8 8.8.8.8 via XX.49.84.238 dev eth1 src XX.49.84.237 cache mtu 1500 advmss 1460 hoplimit 64 – KIT Feb 28 '11 at 16:10
  • Ok, then run tcpdump and ping simultaneity – ooshro Feb 28 '11 at 16:11
  • tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes 10:12:21.522105 IP XX.49.84.237 > 8.8.8.8: ICMP echo request, id 4868, seq 1, length 64 --- times 5 ping 8.8.8.8 PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. ^C --- 8.8.8.8 ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 4033ms – KIT Feb 28 '11 at 16:13
  • arp -a does nothing – KIT Feb 28 '11 at 16:15
  • sudo iptables -nv -L Chain INPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination – KIT Feb 28 '11 at 16:16
  • please add all output in qestion(use edit)... "tracepath -n 8.8.8.8" ? – ooshro Feb 28 '11 at 16:18
  • "arping XX.49.84.238"? – ooshro Feb 28 '11 at 16:19
  • (edit) tracepath -n 8.8.8.8 1: XX.49.84.237 2.146ms pmtu 1500 1: no reply 2: no reply 3: no reply 4: no reply 5: no reply 6: no reply 7: no reply 8: no reply 9: no reply 10: no reply 11: no reply 12: no reply 13: no reply 14: no reply 15: no reply 16: no reply 17: no reply 18: no reply 19: no reply 20: no reply 21: no reply 22: no reply 23: no reply 24: no reply 25: no reply 26: no reply 27: no reply 28: no reply 29: no reply 30: no reply 31: no reply Too many hops: pmtu 1500 Resume: pmtu 1500 – KIT Feb 28 '11 at 16:22
  • arp -a XX.49.84.238 ? (XX.49.84.238) at 00:13:f7:9c:af:98 [ether] on eth1 – KIT Feb 28 '11 at 16:30
  • try again "tcpdump -pni eth1" and "dig google.com @8.8.8.8" – ooshro Feb 28 '11 at 16:44
  • ` tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes 10:49:18.788840 ARP, Request who-has XX.49.84.238 tell XX.49.84.237, length 28 10:49:18.789825 ARP, Reply XX.49.84.238 is-at 00:13:f7:9c:af:98, length 46 10:49:18.789908 IP XX.49.84.237.40104 > 8.8.8.8.53: 61892+ A? google.com. (28) dig google.com @8.8.8.8 ; <<>> DiG 9.7.1-P2 <<>> google.com @8.8.8.8 ;; global options: +cmd ;; connection timed out; no servers could be reached ` – KIT Feb 28 '11 at 16:52
  • try change address to other in the same network – ooshro Feb 28 '11 at 16:56
  • Well...I changed the internet IP to another one in my range (XX.49.84.235) and everything works. Is that a clue as to why this one could be not working? – KIT Feb 28 '11 at 17:02
  • most likely a problem with ISP – ooshro Feb 28 '11 at 17:03
  • Ok. Well thank you very much for your help today. – KIT Feb 28 '11 at 17:04
  • Instead of `arp -a`, you can use `ip neigh`. – sciurus Feb 28 '11 at 18:46