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CCNP Core > Chap 11 - BGP (part 2) > Flashcards

Chap 11 - BGP (part 2) Flashcards

1
Q

What is the series of 6 BGP neighbor states called?

A

BGP Finite State Machine

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2
Q

During the connection process what 3 things happen if an error causes BGP to return to the Idle State?

A
  • ConnectRetryTimer set to 120 seconds
  • New TCP connection is re-tried in 120 seconds
  • Further failures to leave IDLE state causes the timer to double each time
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3
Q

Who manages the connection during the Connect State?

A

The neighbor with the higher IP address.

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4
Q

What 4 things are checked in the OPEN Message that is received in the OpenSent State?

A
  • BGP versions must match
  • Source IP and ASN must match what has been configured locally
  • Router IDs must be unique
  • Security Parameters (password and TTL) must be set appropriately
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5
Q

What are the 3 basic components in configuring BGP?

A
  • BGP Session parameters
  • Address Family Initialization
  • Activate the Address Family on the peer
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6
Q

What 3 commands are used to configure BGP Session parameters?

A
  • router bgp (ASN)
  • bgp router-id (router_ID)
  • neighbor (IP_address) remote-as (neighbor’s AS)
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7
Q

What happens if the router ID is changed after a BGP session has been established?

A

All BGP sessions reset and need to be re-established

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8
Q

What is the default address family that is already activated?

A

IPv4

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9
Q

If the router ID is dynamically configured how does that happen?

A
  • Highest Loopback interface IP address that is up/up
  • Highest Physical interface IP address in an up/up state
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10
Q

What do BGP network statements do?

A

Identify specific network prefixes to be installed into the Loc-RIB table.

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11
Q

In order for a new prefix to be added to the Loc-RIB table what test must it meet?

A

The new route must have an exact match in the Global RIB.

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12
Q

What 3 Path Attributes are set when a Connected Network is added to the Loc-RIB table?

A
  • Next Hop BGP Attribute set to 0.0.0.0
  • BGP Origin Attribute set to I (for IGP)
  • BGP weight set to 32,768
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13
Q

What 4 Path Attributes are set when a Static Route or a route from a Routing Protocol is added to the Loc-RIB table?

A
  • Next Hop BGP Attribute set to Next Hop int the RIB
  • BGP Origin Attribute set to I (for IGP)
  • BGP weight set to 32,768
  • MED attribute set to the IGP metric
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14
Q

What 2 conditions have to be met before a route in the Loc-RIB table is advertised?

A
  • Outbound route policy is applied
  • Route moves to adj-RIB-out
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15
Q

What happens to a route in the Loc-RIB table if its found to be invalid or next hop is not in the RIB?

A

The route remains in the Loc-RIB table but is not processed any further.

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16
Q

What happens to a route in the Loc-RIB table if it isn’t denied by the outbound route policy?

A

The route is moved to Adj-RIB-Out table and advertised to peers

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17
Q

What happens if a route’s Next Hop BGP Attribute is set to 0.0.0.0?

A

BGP changes the Next Hop Attribute to be that of the IP address of the local interface where the advertisement will go out.

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18
Q

How many tables does BGP use when maintaining prefixes and path attributes?

A

3

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19
Q

What are the names of the 3 tables used by BGP?

A
  • Adj-RIB-In
  • Loc-RIB
  • Adj-RIB-Out
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20
Q

What is in the Adj-RIB-In table?

A

Contains the NLRIs learned from peers in original form before any inbound route policies are processed.

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21
Q

What is in the Loc-RIB table?

A

The NLRIs in Loc-RIB have:

  • been received locally or from peers
  • passed the inbound router policy
  • been determined to be the best path
22
Q

Where does the IP Routing Table get its routes from?

A

The Loc-RIB table.

23
Q

What is in the Adj-RIB-Out table?

A

Contains the NLRIs to be advertised to peers after the outbound policies have been applied.

24
Q

How many paths does each entry in the Loc-RIB table contain?

A

At least one but could be more.

25
Q

Why should BGP be thought of as a Routing Application?

A

Because it contains 2 parts - the BGP Session and Route Advertisement

26
Q

When configuring Route Aggregation what is the key word that surpresses the summarized networks from also being advertised?

A

summary-only

27
Q

What does the Atomic Aggregate attribute indicate?

A

That a loss of path information has occurred.

28
Q

What are 2 Optional and Non-transitive attributes in MP-BGP?

A
  • MP_Reach_NLRI
  • MP_Unreach_NLRI
29
Q

What is Multiprotocol Reachable NLRI do?

A

Describes IPV6 Route Information

30
Q

What does Multiprotocol Unreachable NLRI do?

A

Withdraws the IPv6 route from service.

31
Q

When looking at a BGP route what does the weight value of 32,768 mean?

A

That the prefix was originated locally.

32
Q

How does BGP process an incoming route?

A
  • Incoming route stored in adj-RIB-in
  • Inbound routing policy applied
  • BGP decision process selects best route
  • Best route moved to Loc-RIB
  • Validity check
    • is next hop resolvable in Global RIB?
    • If fail - remains in Loc-RIB but not processed further
  • Install BGP best path into Global RIB
  • Route then has outbound route policy applied
  • Route is moved to adj-RIB-out
  • Route is advertised to neighbors
33
Q

How many adj-RIB-in and adj-RIB-out tables are maintained on a BGP router?

A

1 for each peer

34
Q

What ‘show’ command displays a summary of the BGP table and neighbor peering sessions?

A

show bgp <afi> summary

ex. show bgp ipv4 unicast summary

35
Q

What are the 6 BGP neighbor states?

A
  • Idle
  • Connect
  • Active
  • OpenSent
  • OpenConfirm
  • Established
36
Q

Display the TCP session on a BGP router.

A

show tcp brief

37
Q

Verify the BGP session

A

show bgp ipv4 unicast summary

38
Q

Display the BGP neighbors session state.

A

show bgp ipv4 unicast neighbors (ip_address)

39
Q

Display the contents of the Loc-RIB table.

A

show bgp ipv4 unicast

40
Q

Display the contents of the Adj-RIB-Out table for a neighbor.

A

show bgp ipv4 unicast (neighbor_IP) advertised-routes

41
Q

Verify the exchange of NLRIs between nodes.

A

show bgp ipv4 unicast summary

42
Q

Display BGP routes in the Global Routing Table (RIB).

A

show ip route bgp

43
Q

Show if the IPV6 neighbor attributes were negotiated successfully.

A

show bgp ipv6 unicast neighbors 2001::2 detail

44
Q

Display IPV6 BGP routes.

A

show bgp ipv6 unicast 2001:db8::1/64

45
Q

What number range is used by an AS-PATH ACL?

A

1 - 500

46
Q

After a ‘network’ statement has been configured for a Connected network what 5 things happen?

A
  • Global RIB searched for exact match of the prefix
  • Prefix installed in Loc-RIB
  • Next-hop BGP PA set to 0.0.0.0
  • Origin PA set to ‘i’ for IGP
  • BGP Weight PA set to 32,768
47
Q

What are 3 reasons to summarize routes?

A
  • Conserves router resources
  • Accelerates best path calculation
  • Provides stability by hiding route flaps
48
Q

What are the 2 techniques for BGP summarization?

A
  • Static
  • Dynamic
49
Q

What are the commands for configuring Static summary route for 172.21.2.0, 172.21.3.0 and 172.21.4.0?

A

R1(config-router)# network 172.21.0.0 mask 255.255.0.0
R1(config-router)# exit
R1(config)# ip route 172.21.0.0 255.255.0.0 null0

50
Q

What is the command to configure a Dynamic summary route for 172.21.0.0/16 with suppression and preserving the path attributes?

A

R1(config-router)# aggregate-address 172.21.0.0 255.255.0.0 as-set summary-only

CCNP Core (46 decks)

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