Which BGP attribute is used to influence inbound traffic when two peering sessions to the same AS exist?

A.
weight

B.
local preference

C.
router ID

D.
MED

Explanation:
The BGP multiple exit discriminator (MED, or MULTI_EXIT_DISC) is an optional path attribute that can be included in BGP update messages. This attribute is used on external BGP links (that is, on inter-AS links) to select among multiple exit points to a neighboring AS. The MED attribute has a value that is referred to as a metric. If all other factors in determining an exit point are equal, the exit point with the lowest metric is preferred.

If a MED is received over an external BGP link, it is propagated over internal links to other BGP systems within the AS.

BGP update messages include a MED metric if the route was learned from BGP and already had a MED metric associated with it, or if you configure the MED metric in the configuration file in one of the following ways:

* Defining a MED Metric Directly
* Using Routing Policy to Define a MED Metric
* Examples: Configuring the MED Metric

A MED metric is advertised with a route according to the following general rules:

* A more specific metric overrides a less specific metric. That is, a group-specific metric overrides a global BGP metric and a peer-specific metric overrides a global BGP or group-specific metric.
* A metric defined with routing policy overrides a metric defined with the metric-out statement.
* If any metric is defined, it overrides a metric received in a route.
* If the received route does not have an associated MED metric, and if you do not explicitly configure a metric value, no metric is advertised. When you do not explicitly configure a metric value, the MED is equivalent to zero (0) when advertising an active route.

Defining a MED Metric Directly

To directly configure a MED metric to advertise in BGP update messages, include the metric-out statement:

metric-out (metric | minimum-igp offset | igp delay-med-update | offset);

Specify igp to set the metric to the most recent metric value calculated in the IGP to get to the BGP next hop.

In JUNOS Release9.0 and later, you can also specify that a BGP group or peer configured with the metric-out igp statement delay sending MED updates when the MED value increases. Include the delay-med-update statement when you configure the igp statement. The default interval to delay sending updates unless the MED is lower or another attribute associated with the route has changed is 10minutes. Include the med-igp-update-interval minutes statement at the [edit routing-options] hierarchy level to modify the default interval.

Specify a value for offset to increase or decrease the metric that is used from the metric value calculated in the IGP. The metric value is offset by the value specified. The metric calculated in the IGP (by specifying either igp or igp-minimum) is increased if the offset value is positive. The metric calculated in the IGP (by specifying either igp or igp-minimum) is decreased if the offset value is negative.

offset can be a value in the range from 231 through2311. Note that the adjusted metric can never go below0 or above2321.