Question 1.
Which BGP selection criterion is not associated with a BGP attribute?

a) Multi-exit discriminator (MED)
b) AS path prepending
c) Local preference
d) weight

Answer

Question 2.
The configuration on a Cisco 3640 contains router ospf 1 and router ospf 2. What is true about these two statements?

a) The values following "ospf" need to be registered AS numbers
b) They will not share link state database information unless it is explicitly redistributed
c) With these statements, there can be two autonomous system border router functions on this router, even if it does not connect to the Internet
d) With these statements, there can be two autonomous system border router functions on this router, only if there are two distinct Internet connections.

Answer

Question 3.
Which of the following contain policies?

a) BGP router configurations
b) UPDATE messages in the BGP protocol
c) RPSL entries in routing registries
d) BGP NOTIFICATION messages

Answer

Answers

Question 1.
Which BGP selection criterion is not associated with a BGP attribute?

a) Multi-exit discriminator (MED)
b) AS path prepending
c) Local preference
d) weight

Answer
d) weight

Explanation
Weight is a Cisco-specific criterion that does not go beyond the router on which it is configured. BGP attributes are used to carry information to other routers, so weight is not associated with an attribute.

AS_PATH is an attribute, so prepending AS numbers affects this attribute.

Like AS prepending, MED is intended to affect preference in AS other than yours. AS path prepending is a basic and direct mechanism to make paths more or less preferable to a distant (i.e., not directly connected) AS. The MED can affect only directly connected external AS.

Local preference does not propagate outside your AS, but all iBGP speakers will hear it. It is an attribute.

While BGP community attributes are not directly part of the route selection algorithm, you can set administrative weight, MED, or local preference based on community information.
[3135]

CCIE Topic(s): E
CCIE Objective(s): E2
CCNA Topic(s):
CCNA Objective(s):

Question 2.
The configuration on a Cisco 3640 contains router ospf 1 and router ospf 2. What is true about these two statements?

a) The values following "ospf" need to be registered AS numbers
b) They will not share link state database information unless it is explicitly redistributed
c) With these statements, there can be two autonomous system border router functions on this router, even if it does not connect to the Internet
d) With these statements, there can be two autonomous system border router functions on this router, only if there are two distinct Internet connections.

Answer
b) They will not share link state database information unless it is explicitly redistributed
c) With these statements, there can be two autonomous system border router functions on this router, even if it does not connect to the Internet

Explanation
The value following the router ospf is not an autonomous system number. It is an arbitrary process identifier that does not go outside the physical router, and is used simply to separate OSPF processes on the same box. Since the processes are separated, they will not share link state database information unless it is explicitly redistributed.

There can be two autonomous system border router functions on this router, even if it does not connect to the Internet because an ASBR is simply a function that either generates default or imports routing information from a source outside the current OSPF routing domain. OSPF's usage of the term "autonomous system" is not the same usage as in current external/BGP routing.

Choice D is false because OSPF's ASBR function has nothing to do with the more general Internet definition of an AS.
[3136]

CCIE Topic(s): E
CCIE Objective(s): E1,E2
CCNA Topic(s):
CCNA Objective(s):

Question 3.
Which of the following contain policies?

a) BGP router configurations
b) UPDATE messages in the BGP protocol
c) RPSL entries in routing registries
d) BGP NOTIFICATION messages

Answer
a) BGP router configurations
c) RPSL entries in routing registries

Explanation
Choice B and choice D refer to BGP protocol messages. BGP itself does not carry policies, but carries the information that can be used to enforce policies by rules in the routers. The implementation of these rules includes various filters, selective peering, and route selection algorithms. RPSL provides abstractions of the router commands that implement policies.
[3137]

CCIE Topic(s): E
CCIE Objective(s): E2
CCNA Topic(s):
CCNA Objective(s):