Show Interface Tunnel explaination

[jazzlim2004]

Hi,

Can someone explaination to me what does this mean:

Show interface Tunnel

Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps)

Is it the VPN bandwidth? If yes, can we change it?

Thank you

[Leo Laohoo · Accepted solution]

If yes, can we change it?

Yes you can if you are running Advanced IP Services feature (and above).

[Richard Burts]

Kim

Cisco establishes a default value for bandwidth of various interface types. They have chosen a value for tunnel interfaces that is quite low (and I am not sure why this is). You can use the bandwidth command in interface configuration mode of the tunnel to change this default value to something that better reflects your operational environment.

I have lots of respect for my colleague Leo but I wonder about the basis for his assertion that the ability to change the bandwidth is based on the feature set that is running. It is my belief that all feature sets support the ability to change the bandwidth of an interface.

HTH

Rick

[jazzlim2004]

Hi,

I tried using the following command to change my bandwidth but failed.

Admin#conf t
Admin(config)#int tunnel100
Admin(config-if)#tunnel bandwidth transmit 10000
                          ^
% Invalid input detected at '^' marker.

Does the above mean on I'm not running on Advanced IP service feature?  How can I activate it?

Thank you

[Lei Tian · Accepted solution]

Hi Kim,

First of all, the tunnel actual bandwidth is tied to the physical interface. The tunnel bandwidth doesn't limit the actual bandwidth for tunnel interface.

2nd, When you do 'show interface tunnel x', there will be 2 bandwidth.

MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec, ------- this 9 Kbit is the default setting for tunnel interface, you can change it using bandwidth command. This bandwidth value will affect your routing protocol's metric.

  Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps) ----------- this bandwith is used for satellite applications, you can change it using "tunnel bandwidth transmit", which is available after 12.3(7)T. This value will not do anything unless you use satellite applications.

HTH,

Lei Tian

[Richard Burts · Accepted solution]

Kim

To get it to work, in interface config mode (interface tunnel x) use the bandwidth x command.

(do not attempt to configure tunnel bandwidth or tunnel transmit bandwidth parameters).

Try something that looks like this:

interface tunnel 100

bandwidth  10000

HTH

Rick

[jazzlim2004]

Thanks all for the reply.

Actually my concern is whether my traffic is restricted by the Tunnel Bandwidth value.

So based on Lei Tian replied, am I correct to say that my VPN traffic is not limited to any setting in the configuration?

My VPN bandwidth will depend solely on my Internet speed?

But Rick advised the command to change the tunnel bandwidth. What will that affect?

Thank you

[Lei Tian]

Hi Kim,

That is correct. Your VPN bandwidth is not limited to the tunnel bandwidth.

The tunnel bandwidth, the one that can be changed using 'bandwidth' command, will affect the routing protocol's cost calculation. It is recommend to change the tunnel bandwidth reflect the physical interface bandwidth.

HTH,

Lei Tian

[Richard Burts]

Kim

The traffic through a tunnel is not constrained by the bandwidth that is configured on the interface. In fact the configured bandwidth does not constrain the traffic through any kind of interface. Bandwidth is a descriptive parameter of the interface (it describes something about the interface but does not control any aspect of the interface). As Lei Tian says the primary use of bandwidth is calculation of metric by routing protocols (OSPF and EIGRP). Also there is a feature in EIGRP that limits the routing protocol traffic that is sent through the interface (by default EIGRP will not use more than 50% of the configured bandwidth - so if the tunnel defaults to 8K then EIGRP will not use more than 4K for its HELLO and update traffic). The configured bandwidth is used to calculate the per cent busy of an interface and so may impact some Network Management reporting.

When I am configuring a router that will run EIGRP over GRE tunnels I do routinely configure a bandwidth for the tunnel. This is primarily to give EIGRP more capacity to send its updates. But the configured bandwidth does not have any impact on the VPN traffic being sent through the tunnel.

HTH

Rick

[Leo Laohoo]

tunnel bandwidth transmit

Three years ago, we ran into this problem where we could not set the "tunnel bandwidth transmit" command although the Cisco documentations shows that it was possible with IP Base feature set.  So one smart fellow downloaded Advanced IP Services feature set and he noticed that the command worked with Advanced IP Services.  After this event we've tried unsuccessfully to get Cisco to ammend the documents.

Anyway, I thought I may have gotten my facts wrong so I did some experiments ...

IOS version 15.1(1)T SP Services

Router(config-if)#tunnel bandwidth receive ?
<1-10000000>  Bandwidth in kilobits

Router(config-if)#tunnel bandwidth receive
% Incomplete command.

Router(config-if)#tunnel bandwidth transmit ?
<1-10000000>  Bandwidth in kilobits

Router(config-if)#tunnel bandwidth transmit

IOS Version 12.4(25c) IP Base

Router(config)#int tun 1000
Router(config-if)#tunnel bandwidth receive ?
% Unrecognized command
Router(config-if)#tunnel bandwidth receive
                                                ^
% Invalid input detected at '^' marker.

Router(config-if)#tunnel band?
% Unrecognized command

IOS Version 12.4(25c) Advanced IP Services

Router(config)#int tun 1000
Router(config-if)#no shut
Router(config-if)#tunnel bandwidth receive ?
<1-10000000>  Bandwidth in kilobits

Router(config-if)#tunnel bandwidth receive
% Incomplete command.

Router(config-if)#tunnel bandwidth trans
Router(config-if)#tunnel bandwidth transmit ?
<1-10000000>  Bandwidth in kilobits