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BGP Prefix-Filter

Here you will find answers to BGP Prefix-Filter Questions

Question 1

What does the following command accomplish?

sanjose#clear ip bgp 10.1.1.1 in prefix-filter

A. The sanjose router will perform an outbound soft reconfig to the 10.1.1.1 neighbor.
B. The sanjose router will send out the ORF prefix-list so that a new route refresh will be received from the 1.1.1 neighbor. C. The 10.1.1.1 router will perform an inbound soft reconfig on the updates from the sanjose neighbor.
D. The 10.1.1.1 router will send out the ORF prefix-list so that a new route refresh will be received from the sanjose neighbor.
E. The bgp session between the sanjose and the 10.1.1.1 router will be reset so that all the new bgp updates from the 10.1.1.1 router can be processed by the inbound prefix-list at the sanjose router. 
F. The bgp session between the sanjose and the 10.1.1.1 router will be reset so that all the new bgp updates from the sanjose router can be processed by the inbound prefix-list at the 10.1.1.1 router.

 

Answer: B

Question 2

The MPLS VPN provider is using a separate Internet VPN to provide Internet access to its MPLS VPN customers. Currently, all of its customers are not able to access the Internet. The partial provider’s CE-lnternet router configuration is shown below. Based on the configuration, what could be the cause of the problem?

ip route 0.0.0.0 0.0.0.0 10.1.1.1
!
router bgp 51001
network 0.0.0.0
neighbor 10.2.2.2 remote-as 51002 ! PE neighbor router
neighbor 10.2.2.2 prefix-list test1 out
neighbor 10.3.3.3 remote-as 51001 ! Another Internet router
neighbor 10.3.3.3 prefix-list test2 out
!
ip prefix-list test2 permit 0.0.0.0/0
ip prefix-list test1 permit 0.0.0.0/0 ge 1

A. The test2 prefix-list should be applied to the 10.2.2.2 neighbor and the test1 prefix-list should be applied to the 10.3.3.3 neighbor. 
B. Both prefix-lists should be applied in the “in” direction instead of the “out” direction. 
C. The network command is missing the mask 0.0.0.0 option.
D. The network command is missing the mask 255.255.255.255 option. 
E. The neighbor 10.2.2.2 activate and the neighbor 10.3.3.3 activate commands are missing.

 

Answer: A

Categories: BGP + MPLS 642-691 Exam Tags:
  1. NB
    May 11th, 2011 at 05:55 | #1

    can someone explain Q2

  2. Anonymous
    June 24th, 2011 at 13:55 | #2

    @NB: yes

  3. Kit-Kat
    July 20th, 2011 at 11:03 | #3

    can anyone explain q.2 , with something more than a ‘yes’ ?

  4. mady
    July 21st, 2011 at 04:38 | #4

    ip prefix-list test2 permit 0.0.0.0/0 —> why we need to apply test2 on neighbor 10.2.2.2 is its specific route default pefer—
    ip prefix-list test1 permit 0.0.0.0/0 ge 1 —-> test 1 needs to be apply on neighbor 10.3.3.3 normal route, which will check greater than and equal routes

    let me know i am correct?

  5. IPT1
    September 20th, 2011 at 10:52 | #5

    neighbor 10.3.3.3 remote-as 51001 ! Another Internet router
    ## to internet router we have to permit update for default route.. ie.0.0.0.0/0

    neighbor 10.2.2.2 remote-as 51002 ! PE neighbor router
    ## routes permited to send anything except default 0.0.0.0/0 ge 1

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