Why is this Ethernet interface up/up ?

[rakuten02]

The interface is still showing up/up in my router when I am unable to ping the ISP PE router.

The keepalive setting is the default of 10sec, so I would assume the interface would be up/down when the ISP PE router is down?

This Ethernet interface is connected to a ISP PE router with the following settings:

no ip redirects
no ip unreachables
no ip proxy-arp
load-interval 30
delay 5000
duplex full
speed 100

media-type rj45

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

[balaji.bandi]

The most case you connect to NTU, it never goes down - so the connected interface always up/up (depends on the provider) so check the CDP neighbor you can see the PE router.

what kind of circuit delivery?

post the interface status

show interface gi0/0

[rakuten02]

Ah, NTU will always be up? I will check on cdp neighbor when possible.

Show interface:

Hardware is iGbE, address is 
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)

[balaji.bandi]

this output does not show up/up? post complete show interface gi 0/0  -what device is this?

[rakuten02]

It is the same Ethernet interface, just that I missed out the up/up and removed IP addresses for security reasons.

GigabitEthernet0/1 is up, line protocol is up
Hardware is iGbE, address is 
Internet address is 
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 1y3w, output 00:00:00, output hang never
Last clearing of "show interface" counters 4w3d
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
410518 packets output, 54818378 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

[balaji.bandi]

-what device is this?  can you post-show version?

what is the outcome if you remove the cable from Gi 0/1 ? is the interface still up?

[rakuten02]

Cisco IOS Software, C3900e Software (C3900e-UNIVERSALK9-M), Version 15.4(3)M3, RELEASE SOFTWARE (fc2)

Cisco CISCO3945-CHASSIS (revision 1.0) with C3900-SPE250/K9 
8 Gigabit Ethernet interfaces
1 Virtual Private Network (VPN) Module

I am unable to remove the cable as the device is at a remote site. 

[balaji.bandi]

Looks it connect to NTU so i believe that is the reason this up all time, but it did not have any traffic for long. as provider to test NTU off the port and check.

[rakuten02]

Verified that the ISP PE router or NTU is not showing up as a CDP neighbor.

[MHM Cisco World]

Are you use ISP PE as L2 or L3VPN ?

[rakuten02]

L3VPN.

[MHM Cisco World]

the only reason there is L2 between CE and PE and this make the link UP/UP.

[rakuten02]

What would be a possible L2 between the CE & PE? Thanks!