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We recently had a new Ethernet connection installed and were given the WAN IP address, subnet mask and gateway needed for the connection e.g.

IP   1.2.3.50  
MASK /30  
GW   1.2.3.49  

When I put these details into my laptop and connect it to the NTU, I can ping outside. If I configure the cisco router however, no such luck.

I originally just changed the interface details and default route on the cisco but this wouldn't work. Out of frustration I erased the config (after backing it up to text file) and started again from scratch but I still cannot ping outside.

Since we are starting with a fresh config, there is currently no NAT or ACLs that could have an impact on this. This is an excerpt from the Cisco config as it stands now:

!  
interface FastEthernet4  
  ip address 1.2.3.50 255.255.255.252  
  speed auto  
  duplex auto  
!  
ip route 0.0.0.0 0.0.0.0 1.2.3.49  
!  

When the cable is connected from the Cisco Fa4 to the NTU, both the port and line protocol come up. Here is the output from "show interface fa4"

FastEthernet4 is up, line protocol is up  
  Hardware is PQII_PRO_UEC, address is 7c0e.ced6.3997 (bia 7c0e.ced6.3997)  
  Internet address is 1.2.3.50/30  
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,  
     reliability 255/255, txload 1/255, rxload 1/255  
  Encapsulation ARPA, loopback not set  
  Keepalive set (10 sec)  
  Full-duplex, 100Mb/s, 100BaseTX/FX  
  ARP type: ARPA, ARP Timeout 04:00:00  
  Last input 00:00:00, output 00:00:00, output hang never  
  Last clearing of "show interface" counters never  
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0  
  Queueing strategy: fifo  
  Output queue: 0/40 (size/max)  
  5 minute input rate 1000 bits/sec, 2 packets/sec  
  5 minute output rate 0 bits/sec, 0 packets/sec  
     59979 packets input, 5826666 bytes  
     Received 48113 broadcasts (0 IP multicasts)  
     0 runts, 0 giants, 0 throttles  
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored  
     0 watchdog  
     0 input packets with dribble condition detected  
     3548 packets output, 329680 bytes, 0 underruns  
     0 output errors, 0 collisions, 1 interface resets  
     2518 unknown protocol drops  
     0 babbles, 0 late collision, 0 deferred  
     0 lost carrier, 0 no carrier  
     0 output buffer failures, 0 output buffers swapped out  

The only thing that stands out to me is the line "2518 unknown protocol drops" but what does this mean?

If it helps I am using a Cisco 881 router and it is interfacing with a MRV OS-904

Anyone had any similar issues like this?? I cant for the life of me figure out why there is a difference between using my laptop and the cisco router.

Any help would be much appreciated!

  • Need more information here . . . Are you pinging from the Cisco, do you have NAT on the Cisco, have you looked at your ARP tables, have you tried connecting your laptop to the Cisco (with the laptop taking the place of the NTU)? Do you even get the Ethernet link? What does show interface say? Your Cisco could be configured with a forced data rate on the Ethernet interface that is incompatible with the NTU interface. – Law29 Jun 17 '16 at 6:43
  • Yes i am pinging directly from the cisco. No NAT. ARP tables only shows the configured interface and a "unknown" entry for the gateway IP. Please see edits above @Law29 – plunkos Jun 22 '16 at 2:56

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