"Reasons for Failure to Advertise 200.1.0.0/16 Prefix in BGP"
Question
-- Exhibit --
user@router# run show route advertising-protocol bgp 192.168.12.1 user@router# run show route inet.0: 11 destinations, 12 routes (11 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
2.2.2.2/32 *[Direct/0] 3w6d 03:57:51
> via lo0.0
192.168.12.0/24 *[Direct/0] 01:07:34
> via xe-0/0/0.0
192.168.12.2/32 *[Local/0] 01:07:34
Local via xe-0/0/0.0 -
200.1.0.0/16 *[Aggregate/130] 00:00:58
Reject -
[IS-IS/165] 00:10:57, metric 10
> to 200.1.1.2 via xe-0/0/3.0
200.1.1.0/24 *[Direct/0] 00:29:21
> via xe-0/0/3.0
200.1.1.1/32 *[Local/0] 00:29:21
Local via xe-0/0/3.0 -
iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
49.0000.0020.0200.2002/72
*[Direct/0] 3w4d 21:07:32
> via lo0.0
inet6.0: 3 destinations, 4 routes (3 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
2:2:2::2/128 *[Direct/0] 3w4d 21:22:24
> via lo0.0
[edit]
user@router# show policy-options
policy-statement adv-route {
term t1 {
from {
protocol isis;
route-filter 200.1.0.0/16 exact;
}
then accept;
}
term t2 {
then reject;
}
}
[edit]
user@router# show protocols bgp
group ebgp {
type external;
export adv-route;
neighbor 192.168.12.1 {
peer-as 65000;
}
}
-- Exhibit --
Click the Exhibit button.
Referring to the exhibit, why is the 200.1.0.0/16 prefix failing to be advertised in BGP?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.D
Based on the exhibit provided, the 200.1.0.0/16 prefix is failing to be advertised in BGP because it is being rejected by the policy defined in the "adv-route" policy statement. This can be seen from the output of the "show policy-options" command, which shows the following policy:
pythonpolicy-statement adv-route { term t1 { from { protocol isis; route-filter 200.1.0.0/16 exact; } then accept; } term t2 { then reject; } } The "adv-route" policy statement has two terms defined. The first term, "t1," matches routes that have an ISIS protocol origin and belong to the 200.1.0.0/16 network, and then accepts them. The second term, "t2," does not match any routes and then rejects them.
Since there is no explicit "accept" action defined for the aggregate route for the 200.1.0.0/16 prefix, it falls through to the second term of the policy statement, which rejects the route.
Therefore, option B, "The aggregate route is set to reject," is the correct answer. The policy defined in the "adv-route" policy statement is applied to the BGP neighbor 192.168.12.1, as specified in the configuration of the "ebgp" BGP group. The policy is applied to both internal and external BGP routes, as there is no specific "type internal" or "type external" specified in the policy terms. Option C is incorrect because the policy is being applied to an external BGP neighbor. Option A is also incorrect because there is no indication that next-hop self is needed for the prefix to be advertised, and option D is incorrect because the IS-IS route is not being considered for advertising in BGP due to the policy being applied.
