what does tunnel up line up means

Unanswered Question
Mar 20th, 2008

Tunnel1 is up, line protocol is up

Hardware is Tunnel

Internet address is

MTU 1514 bytes, BW 1000 Kbit, DLY 10000 usec,

reliability 255/255, txload 2/255, rxload 1/255

Encapsulation TUNNEL, loopback not set

Keepalive not set

Tunnel source (FastEthernet0), destination UNKNOWN

Tunnel protocol/transport multi-GRE/IP

Key 0x186A0, sequencing disabled

Checksumming of packets disabled

Tunnel TTL 255

Fast tunneling enabled

Tunnel transmit bandwidth 8000 (kbps)

Tunnel receive bandwidth 8000 (kbps)

Tunnel protection via IPSec (profile "vpnprof")

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: 0/0 (size/max)

5 minute input rate 4000 bits/sec, 4 packets/sec

5 minute output rate 8000 bits/sec, 6 packets/sec

7165427 packets input, 1206831456 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

8165531 packets output, 1473160831 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

NVI0 is up, line protocol is up

I have this problem too.
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Richard Burts Thu, 03/20/2008 - 09:29


In general when IOS says that an interface is up and line protocol is up it means that the IOS believes that the interface is functioning properly and will correctly send and receive traffic. Part of the determination of this is the successful sending and receiving of keepalive messages.

But GRE tunnels are a bit different. In particular GRE tunnels do not perform keepalives by default. This is confirmed by this line of your output:

Keepalive not set

So for the GRE tunnel the indication of up/up indicates that the router believes that it can successfully get to the next hop address on the way to the tunnel destination (and since this appears to be a multipoint GRE tunnel there is potentially more than one destination address):

Tunnel protocol/transport multi-GRE/IP

So this router believes that tunnel 1 if functioning and can send and receive traffic.



mahesh18 Thu, 03/20/2008 - 09:40

thanks for ur reply

so is the interface Tunnel1 a logical interface or physical interface ?

mahesh18 Thu, 03/20/2008 - 09:48

so the address

Internet address is

is address of ligical interface of the tunnel?

meballard Thu, 03/20/2008 - 09:52

That is the IP address of the tunnel. All communications that pass through the tunnel (not the tunnel itself, just the communications that pass through the tunnel) use that IP address on that end of the tunnel, ie the next/previous hop for routers on the other end of the tunnel when going to/from networks connected to the router this configuration is from.

mahesh18 Thu, 03/20/2008 - 10:03

Tunnel source (FastEthernet0), and this is source ip

of tunnel.

so what is difference between ip of tunnel

itself and souce ip of tunnel?

Richard Burts Thu, 03/20/2008 - 10:12


The IP address of the tunnel ( would be the source address used for any packet generated by the tunnel interface (for example if you ping the remote end of the tunnel the source address would be your tunnel interface address ( and the destination address would be the tunnel address of the other end of the tunnel.

The source address of the tunnel ( is the address of the tunnel packet as it is sent out the physical interface. If some packet came to the router to be forwarded it would have its own source and destination addresses. If that packet were to be forwarded through the tunnel interface then what GRE does is to encapsulate the original IP packet in a new IP header. In the new IP header the source address is the tunnel source address (




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