Protocol and Metric

[communication.boy]

Some routing protocols use bandwidth to calulcate the metric of route ( EIGRP , OSPF etc ) . In a simple network where the terminated link is on FastEthernet but bandwidth is 128K , will the routing protocol just consider FastEthernet i.e. 100mbps or will detect somehow that link is of 128K by sending data to the other end host .

Will it be required to hardcode bandwidth value under physical interface or tunnel interface for efficient communication ?

[smehrnia · Accepted solution]

Hi boy,

each interface type has a default bandwidth value in (kbps) to be used by higher protocols (OSPF, EIGRP, etc) and the routing protocol uses that value for metric calculations i.e. Serial interface: 1544 Kbps. not the actual transmission speed or rate limit value. although you can define a bandwidth value for routing protocols use by Bandwidth interface command.

HTH,

plz Rate if it helped,

Soroush.

[John Blakley]

In addition to what Soroush stated, yes you'll need to set a bandwidth statement on your interface to 128. This value will also be used by qos in order to know how to perform actions on certain types of traffic. Interfaces always send at line rate. If you have 128k CIR and you have an ethernet interface connected to it, the interface is going to send at 100Mb and the other end is probably (unless you control the other end) policing your traffic at the 128k rate which ultimately is going to lead to dropped traffic. You'd want to shape the traffic outbound at 128k if your CIR is 128.

HTH,

John