MPLS GRE Tunnel

Answered Question
Nov 11th, 2008
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We have a branch office connected via 6Mpbs MPLS, but they use a GRE tunnel to allow for static route redistribution. My question is, since the tunnel is configured for 9Kbit, it will not use the available bandwidth for the MPLS 6Mbps?



router-nj01#sh int tunnel 2

Tunnel2 is up, line protocol is up

Hardware is Tunnel

Description: Tunnel to Indianapolis

Internet address is 192.168.150.6/30

MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec,

reliability 255/255, txload 217/255, rxload 1/255

Encapsulation TUNNEL, loopback not set

Keepalive not set

Tunnel source 172.40.0.10, destination 172.40.0.6

Tunnel protocol/transport GRE/IP

Key disabled, sequencing disabled

Checksumming of packets disabled

Tunnel TTL 255


router-nj01#sh interfaces ser1/0

Serial1/0 is up, line protocol is up

Hardware is DSXPNM Serial

Internet address is 172.40.0.10/30

MTU 4470 bytes, BW 6015 Kbit, DLY 200 usec,

reliability 255/255, txload 10/255, rxload 26/255

Encapsulation HDLC, crc 16, loopback not set

Keepalive set (10 sec)

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Correct Answer by Edison Ortiz about 8 years 8 months ago

then that will be the maximum amount flowing over the MPLS?


No, the limiter will be based on the physical interface used for traversing from tunnel-to-tunnel.


For instance, if the tunnel is using the serial interface as the source and another serial interface as the destination (based on both serial running 1.5Mbps) then the speed of the tunnel will be 1.5Mbps.


HTH,


__


Edison.


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Edison Ortiz Tue, 11/11/2008 - 10:46
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The bandwidth value under the show interface output is only useful for QoS and Dynamic Routing Protocols.


It does not limit the amount of traffic the interface can service.


You can modify this value with the bandwidth command under the tunnel interface.


HTH,


__


Edison.

jgorman1977 Tue, 11/11/2008 - 10:48
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so, if I leave the tunnel bandwidth as is (currently 9Kbit), then that will be the maximum amount flowing over the MPLS?

Correct Answer
Edison Ortiz Tue, 11/11/2008 - 10:52
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then that will be the maximum amount flowing over the MPLS?


No, the limiter will be based on the physical interface used for traversing from tunnel-to-tunnel.


For instance, if the tunnel is using the serial interface as the source and another serial interface as the destination (based on both serial running 1.5Mbps) then the speed of the tunnel will be 1.5Mbps.


HTH,


__


Edison.


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bmbreer Tue, 11/11/2008 - 11:02
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The speed of the link is not determined by the bandwidth command. The actual speed of the link is determined by the clockrate set at the provider side(DCE).


On your serial interface you could use the bandwith command to change the BW value to 100000 Kbit when you use the show interface command. That doesn't mean the speed of the link is 100Mbps. The BW value is just used by the routing protocol to make accurate determinations as to what the best path is as well as QoS.

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