关于tunnel带宽参数的讨论

篠郝同学

sh inter tunnel 接口可以看到两个关于带宽的参数。
MTU 17916 bytes, BW 100 Kbit/sec, DLY 50000 usec

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

在tunnel接口下，可以修改后面2个参数。查阅相关资料和网上信息后，有说修改任何一个数值都不影响实际的转发速率，这个参数只会影响需要计算带宽的相关协议，如ospf。有说会影响tunnel接口的速率的。
第一种说法，如果是正确的话，那么结合官网说法，那么就好理解了，简单理解就是影响路由计算cost,实际转发的话，应该是以源的物理带宽来看，但是这样一来，tunnel接口的参数中的关于reliability 255/255, txload 1/255, rxload 1/255等参数又有什么意义呢？
第二种说法，我自己就是是受tunnel bandwidth这个影响，单独划出且只能修改接收发送，我就不好理解了，但是使用范围里面说是卫星带宽，使我又有所怀疑。按第二种说法的话，BW和transmit/receive又有何联系呢？

新人入坑，请多关照！

Step 4

bandwidth kbps Example: Router(config-if)# bandwidth 1000

Sets the current bandwidth value for an interface and communicates it to higher-level protocols. Specifies the tunnel bandwidth to be used to transmit packets. Use the kbpsargument to set the bandwidth, in kilobits per second (kbps). Note    This is a routing parameter only; it does not affect the physical interface. The default bandwidth setting on a tunnel interface is 9.6 kbps. You should set the bandwidth on a tunnel to an appropriate value.

tunnel bandwidth

To set the transmit bandwidth used by the tunnel interface, use the tunnel bandwidth command in interface configuration mode. To restore the default setting, use the no form of this command.

tunnel bandwidth { receive | transmit } bandwidth

no tunnel bandwidth

Syntax Description

receive	Specifies the bandwidth to be used to receive packets through the tunnel. Note This keyword is no longer used and will be removed in future releases.
transmit	Specifies the bandwidth to be used to send packets through the tunnel.
bandwidth	Bandwidth, in kbps. Range is from 0 to 2147483647. Default is 8000.

Command Default

8000 kbps

Command Modes

Interface configuration

Command History[td]

Release	Modification
12.3(7)T	This command was introduced.

Usage Guidelines

Use the tunnel bandwidth command to specify the capacity of the satellite link.

chenl202

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