Siemens S223 User Manual

User Manual                                                                               UMN:CLI 
SURPASS hiD 6615 S223/S323 R1.5 

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During the best-path selection process, the switch compares weight, local preference and 
as-path in turn among the similar parameters of BGP routers. Then, the MED is consid-
ered when selecting the best path among many alternative paths. 

The hiD 6615 S323, MED comparison is configured only among all paths from the 
autonomous system. You can configure the comparison of MEDs among all BGP routers 
within autonomous system. In addition, MED is used when comparing of routes from the 
neighboring routers placed within different AS. 

To find the best route by comparing MED values, use the following command. 

 

Configures the router to consider the comparison of 
MEDs in choosing the best path from among paths. 

Router 

Chooses the best path regardless of the comparison of 
MEDs. 

 

Meanwhile, when the best-path is selected among the neighbor routers within same 
Autonomous System, it doesn’t compare MED values of them. However, in case the 
paths have same AS-path information, it does compare MED values. If there are two 
paths with different AS-path each other, the comparison of MED is unnecessary work. 
Other parameter’s path information can be used to find the best path. 

To compare MED values in order to choose the best path among lots of alternative paths 
included same AS-path value, use the following command. 

 

Configures the router to compare MEDs in choosing 
the best path when paths have same AS-path informa-
tion. 

Router 

Configures the router not to compare MEDs even if the 

paths have same AS-path. 

 

During the best-path selection process, use the bgp always-compare-med command in 
case of comparing MED values regardless of AS-path. Otherwise, use the bgp 
deterministic-med

 command if it compares MED values of lots of paths contained same 

AS-path information. 

 

There are a lot of path parameters BGP protocol, which are IP address, AS, MED value 
and router ID. Even if two paths look same under the condition of IP address, they are ac-
tually different when other parameters are compared with each other.