Tunnel Interface Bandwidth

Answered Question

Hi we have a 3825 router running tunnels to various sites. See the config below: -


interface Tunnel4

bandwidth 1024

ip address 172.16.151.1 255.255.255.0

ip virtual-reassembly

tunnel source 10.128.6.30

tunnel destination 10.207.100.6

tunnel mode ipsec ipv4

tunnel protection ipsec profile VTI


my concern is that the bandwidth setting, they have a 10mb connection but it's been set to 1024 bandwidth.


My questions are: -


If i remove the bandwidth command what will it default to?


Is it best to fix the bandwidth at the same speed of the link


If I make the change will the tunnel go down as the bandwidth will be mismatched for a short period of time?

Correct Answer by attrgautam about 8 years 11 months ago

nopes bandwidth has no impact on the speed of the link...It is more logical from a QOS and routign protocol perspective

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attrgautam Tue, 06/03/2008 - 06:47
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Specifically to each of your questions,


a) if you remove the bandwidth command it will default to 100 KBit.

b) No this is needed at all. You dont need to set bandwidth at all on the tunnel as it is used primarily in QOS buffer calculations and Routing protcols Metric calculations

c) Nopes there is no impact on the IPSEC/VTI tunnels with the Bandwidth command

Correct Answer
attrgautam Tue, 06/03/2008 - 07:29
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nopes bandwidth has no impact on the speed of the link...It is more logical from a QOS and routign protocol perspective

royalblues Tue, 06/03/2008 - 06:50
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If i remove the bandwidth command what will it default to?

It would default to 9K


Is it best to fix the bandwidth at the same speed of the link

Yes, unless you manipulate it to modify routing selection


If I make the change will the tunnel go down as the bandwidth will be mismatched for a short period of time?

No, the tunnel does not go down when you chnage the command. The Bandwidth command however might have influenced the routing algortithm which u might need to consider. QoS configuration also depends on the bandwidth you specify under the interface


HTH

Narayan


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