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CCNP Core > Chap 12 - Advanced BGP (part 1) > Flashcards

Chap 12 - Advanced BGP (part 1) Flashcards

1
Q

What is BGP’s default behavior when multihoming?

A

To install only the best path to the RIB which means only one path for a network prefix is used when forwarding network traffic to a destination.

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2
Q

What are 3 factors an organization considers when choosing a second service provider?

A
  • Cost
  • Circuit availability for remote locations
  • Separation of the control plane
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3
Q

What’s the risk of using more than one service provider?

A

The organization’s AS might become a Transit AS.

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4
Q

How can transit routing be avoided?

A

By applying outbound BGP route policies that only allow for local BGP routes to be advertised to other AS’s.

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5
Q

How can transit routing be avoided at branch sites?

A

Configure route filtering at each branch so that branch sites do not advertise what they learn from the WAN.

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6
Q

If transit routing is to be used what are 4 restrictions?

A
  • Data Centers
  • Proper routing design accomodates outages
  • Bandwidth is sized accordingly
  • The routing pattern is bi-directional and predictable
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7
Q

How do Standard ACLs define packets?

A

Based on the source network only.

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8
Q

What 5 things can Extended ACLs filter on?

A
  • Source
  • Destination
  • Protocol
  • Port
  • Other packet attributes
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9
Q

How are Standard ACLs identified?

A
  • Range 1 to 99
  • Range 1300 to 1999
  • Named
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10
Q

How are Extended ACLs identified?

A
  • Range 100 to 199
  • Range 2000 to 2699
  • Named
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11
Q

What are the 2 parts that a prefix match specification contains?

A
  • High order bit pattern (network)
  • High order bit count (mask)
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12
Q

What does the following prefix match? 10.168.0.0/13 ge 24

A
  • Bit count is 13
  • Bit pattern has to match the first 13 bits of 10.168.0.0
  • First octet must be 10.
  • First 5 bits of the second octet must be binary 10101 to match 168
  • Network mask has to be /24 or greater
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13
Q

What is the regex to start a string?

A

^ Caret

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14
Q

What is the regex to end a string?

A

$ Dollar sign

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15
Q

What is the regex to match a space.

A

_ Underscore

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16
Q

What is the regex to match a single character?

A

[] Match whatever character is inside the brackets

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17
Q

What are the 4 components of a route map?

A
  • Sequence number
  • Conditional matching criteria
  • Processing action
  • Optional action
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18
Q

In a route map what is the Conditional Matching Criteria

A

Identifies prefix characteristics like network, BGP Path Attribute, next hop, etc.

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19
Q

In a route map what is the Processing action?

A

Permit or Deny

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20
Q

In a route map what is Optional Action?

A

Can include modification, addition, or removal of route characteristics

21
Q

What are 6 Match Options for a route map?

A
  • match as-path (acl)
  • match ip address
  • match ip address prefix-list (prefix_list)
  • match local-preference (local_pref)
  • match metric (metric)
  • match tag (tag)
22
Q

In a route map with multiple Match Variables how many variables must match for the prefix to qualify?

23
Q

In a route map with multiple Match Options ( statements ) how many must be met for the prefix to qualify?

A

All of them.

24
Q

In route maps what are 7 Optional Actions?

A
  • set as-path prepend
  • set ip next-hop
  • set local-preference
  • set metric
  • set origin
  • set tag
  • set weight
25
In a route map with multiple sequences by default how are they processed?
Route map processing stops when the first sequence has been matched.
26
In a route map what does the keyword 'continue' do?
It allows the route map to continue processing even if there has been a match.
27
When are inbound route policies executed?
Inbound route policies are executed when the route is in the Adj-RIB-in and before it gets to the Loc-RIB table.
28
When are outbound route policies executed?
Outbound route policies are executed before the route gets to the Adj-RIB-out.
29
What are 4 methods of filtering routes inbound or outbound?
* Distribute list * Prefix list * AS Path ACL filtering * Route maps
30
What does a Distribute List do?
* Prefixes are filtered based on an ACL. * Has an implicit deny.
31
What is a Prefix List?
* A prefix list is a list of prefix-matching specifications permitting or denying processed in a top down fashion. * Has an implicit deny
32
What is an AS Path ACL and what numbering range does it have?
* It’s a list of regex commands that permit or deny based on the current AS-Path value. * Has an implicit deny * 1 - 500
33
What do Route Maps do?
Conditional matching on a variety of prefix attributes and taking a variety of actions.
34
Can a BGP neighbor use a distribute list and a prefix list at the same time?
No
35
What are two methods of clearing BGP connections?
* Hard reset - tears down the BGP session, removes routes from peer, the most disruptive * Soft reset - invalidates BGP cache, request a fully advertisement from peer
36
What are BGP Communities?
* 32-bit field used for tagging routes or modifying routing policy on upstream or downstream routers * Optional Transitive BGP Attribute * Traverses from AS to AS
37
What are 3 well-known Communities?
* Internet - identifies routes that should be advertised on the Internet * No\_Advertise - don't advertise to any BGP peer * No\_Export - only advertise to iBGP peers
38
What range of numbers are used for Standard Community Lists?
1 to 99
39
What range of numbers are used for Extended Community Lists?
100 to 500
40
What is the difference between a Standard Community List and an Extended Community List?
* Standard Community Lists match on well-known communities or private communities. * Extended Community Lists match using regex commands
41
For BGP Communities what is the 'new format' and how many bits for each number?
Two 16 bit numbers as in 100:12345
42
Do IOS router display Communities by default?
No
43
What is the format for a Private BGP Community?
AS number separated with a colon followed by a number assigned by the AS.
44
What is the command that will change the display of a Community to the new format?
ip bgp community new-format
45
What 4 events cause BGP to calculate a new best path?
* BGP next-hop reachability change * Failure of an interface that connects to BGP peer * Redistribution change * Reception of a new or removed paths for a route.
46
What is the first thing BGP looks at when calculating the best path?
Longest match ( /25 would be preferred over a /24)
47
Display the current BGP table, based on routes that meet a specified AS path regex pattern
show ipv4 unicast bgp regexp
48
Display the current BGP table, based on routes that meet a specified BGP community
show bgp community
49
What are the number ranges for standard and extended community lists?
* Standard is 1 - 99 * Extended is 100 - 500

CCNP Core (46 decks)

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