How to Ensure Usable Routes with Junos Policy Options
Question
-- Exhibit --
-- Exhibit --
[edit]
user@Router-X# show policy-options
policy-statement nhs
term 1 {
from {
protocol bgp;
neighbor 10.0.21.2;
}
then next-hop self;
}
}
A Junos device has an external peering session to 10.0.21.2 and several internal peers.
How can the policy reference in the exhibit be used to ensure routes are usable?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.B
As a best practice, always apply a next-hop self policy as an export policy to internal peers or to the BGP group to wich those peers belong. Improper application of a next-hop-self policy can cause suboptimal routing or result in hidden routes.
The policy statement "nhs" shown in the exhibit is a BGP policy that matches on incoming BGP routes from the neighbor with IP address 10.0.21.2 and sets the next-hop to the local router's address (self).
To ensure that the routes learned from the external BGP neighbor 10.0.21.2 are usable, the policy statement "nhs" can be applied as an export policy to external BGP peers. This will ensure that when the Junos device sends BGP updates to its external peers, it advertises the routes with the next-hop set to its own IP address.
Alternatively, the policy statement "nhs" could also be applied as an import policy to internal BGP peers. This will ensure that when the Junos device receives BGP updates from its internal peers, any routes learned from the external BGP neighbor with the IP address 10.0.21.2 will have their next-hop set to the local router's address (self), making the routes usable.
Therefore, the correct answer could be either A. Apply it as an import policy to internal BGP peers or D. Apply it as an export policy to external BGP peers, depending on the specific requirements of the network.
