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Computer Networking > CCNP Route > Flashcards

CCNP Route Flashcards

1
Q

List IPv4 Header Fields and their width in bits

A 
Version (4)
Header Length (4)
Type of Service (8)
Total Length (16)
Identification (16)
IP Flags (3)
Fragment Offset (13)
Time to Live (8)
Protocol (8)
Header Checksum (16)
Source Address (32)
Destination Address (32)
IP Option (variable)
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2
Q

What is the IPv4 Identification field?

A

If the packet is fragmented this field will identify which packet the fragments belong to.

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3
Q

What is the IPv4 IP Flags field?

A

3 bits
1 - reserved (0)

2 - DF (Don’t Fragment)

3 - MF (More Fragments) - set on all fragmented packets except the last one.

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4
Q

How do IPv4 fragments get put back together?

A
  • MF bit set to 1 on all except the last packet
  • Fragment Offset dictates the order
  • Identification field dictates which packet the fragments belong to
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5
Q

List common IPv4 protocol numbers

A 
1 - ICMP
2 - IGMP
6 - TCP
17 - UDP
47 - GRE
50 - ESP
51 - AH
88 - EIGRP
89 - OSPF
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6
Q

Describe ARP request and reply. What are the source/destination MAC addresses and source/destination IP addresses.

A

ARP request - source MAC of requester, broadcast MAC (00:00:00:00:00:00:00) for destination, source IP of requester, destination IP of replier

ARP reply - source MAC of replier, destination MAC of requester, source IP of replier, destination IP of requester

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7
Q

Configure a DHCP server for the 192.168.12.0/24 network which excludes IP 192.168.12.100 and sets the gateway to 192.168.15.1, DNS to 8.8.8.8, and points IP phones to a TFTP server at 92.168.12.200.

A 
hostname DHCP
!
interface FastEthernet0/0
 ip address 192.168.12.1 255.255.255.0
!
ip dhcp excluded-address 192.168.12.100
!
ip dhcp pool MYPOOL
 network 192.168.12.0 255.255.255.0
 default-router 192.168.12.1
 dns-server 8.8.8.8
 option 150 ip 192.168.12.200
!
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8
Q

Describe what happens when a DHCP discover packet is relayed.

What is the source and destination IP of the relayed packet?

A
  • The broadcast packet is re-encapsulated sent as a unicast packet to the server.
  • When it is sent a field called giaddr (Gateway Address) is added. It adds the IP of the interface on which the DHCP packet was received into this field.

The source is the interface IP and the destination is the IP of the DHCP server.

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9
Q

What show command will let one see if a DHCP relay is configured

A

‘show ip interface’

Output will have:
Helper address is x.x.x.x

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10
Q

List fields and lengths of UDP header

A 
source port (16)
destination port (16)
UDP length (16)
UDP checksum (16)
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11
Q

List basic UDP bullet points

A

It operates on the transport layer of the OSI model.
Is a connectionless protocol, does not setup a connection…just sends data.
Limited error correction because we have a checksum.
Best-effort or unreliable protocol.
No data-recovery features.

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12
Q

List TCP header fields in order

A 
Source port (16)
Destination port (16)
Sequence (32)
Acknowledgement (32)
Data Offset (4)
Reserved (6)
Flags (6)
Window (16)
Checksum (16)
Urgent Pointer (16)
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13
Q

Describe the TCP sequence number field and its use.

A
  • 32 bit
  • random initial value
  • receiver sends back ack based on this value (
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14
Q

Describe the TCP acknowledgement number and its use

A
  • the receiver requests the next segment by increment the last received sequence number by 1 and placing it in this field
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15
Q

Data Offset

A

Length of TCP header

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16
Q

What is RSV field in TCP used for

A

Nothing - always set to 0

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17
Q

List TCP flags

A 
URG - urgent pointer 
ACK - 
PSH - Tells application to transmit data immediately and don't fill entire segment
RST - Used to reset the connection
SYN - Used for 3 way handshake
FIN - Used for normal end of session
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18
Q

What is the TCP window field and what is it used for?

A
  • 16 bit

- Specifies number of bytes receiver is willing to receive.

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19
Q

What is the urgent pointer field in TCP?

A

When the URG bit has been set the urgent pointer indicates where the urgent data ends.

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20
Q

How do you calculate the bandwidth delay product?

A

bandwidth (bits per sec) x round trip time (in seconds)

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21
Q

List basic ICMP header fields

A

Type (8)
Code (8)
Checksum (16)

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22
Q

List major ICMPv4 type values

A 
0 - echo reply
3 - destination unreachable
5 - redirect
8 - echo
11 - time exceeded
13 - Timestamp
14 - Timestamp reply
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23
Q

List common codes for ICMP destination unreachable

A 
0 - net unreachable
1 - host unreachable
2 - protocol unreachable
3 - port unreachable
4 - fragmentation needed and df set
5 - source route failed
6 - destination network unknown
7 - destination host unknown
8 - source host isolated
9 - communication with destination network is administratively prohibited
10 - communication with destination net is administratively prohibited
13 - Communication administratively prohibited
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24
Q

List 3 problems that may be experienced if routing is asymmetric

A
  • NAT failures
  • Stateful inspection failures
  • Unicast flooding
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25
Q

What is unicast flooding

A

This happens when a switch unintentionally floods unicast packets. If routing is asymmetric the switch on the return path may not learn the MAC address from the transmitting host.

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26
Q

What is needed to become an EIGRP feasible successor

A
  • Must not be the successor

- The advertised distance < feasible distance of successor

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27
Q

How does one configure EIGRP unequal cost load balancing?

A

router mode:

variance <i>multiplier</i>

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28
Q

What protocol does EIGRP use for communication?

A

RTP (Reliable Transport Protocol) - IP protocol number 88

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29
Q

How are EIGRP hello packets sent on a multi-access network?

A

Multicast to 224.0.0.10

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30
Q

List EIGRP packet types

A 
Hello
Update
Query
Reply 
ACK
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31
Q

What are the administrative distances of the major routing protocols?

A 
Directly connected: 0
Static: 1
EIGRP Summary 5
EBGP 20
EIGRP 90
IGRP 100
OSPF 110
IS-IS 115
RIP 120
EGP 140
ODR 160
EX EIGRP 170
iBGP 200
NHRP 250
Floating Static (ex. DHCP-learned) 254
Unknown 255
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32
Q

What is the command to view the EIGRP neighbor table and what information is contained in it?

A

show ip eigrp neighbors

Lists all directly connected neighbors

  • H (Handle) - first neighbor gets 0 - next one 1 - gaps get filled
  • Next Hop IP
  • Interface
  • Hold Time
  • Uptime
  • SRTT (Smooth round trip time)
  • RTO (retransmission timeout)
  • Q Count
  • Seq Number
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33
Q

List codes in EIGRP topology table

A 
P - Passive
A - Active
U - Update
Q - Query
R - Reply
r - reply Status
s - sia Status
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34
Q

When troubleshooting EIGRP what command shows active routes?

A

show ip eigrp topology active

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

A 10.100.1.1/32, 1 successors, FD is Inaccessible
1 replies, active 00:00:56, query-origin: Successor Origin
via 10.2.1.2 (Infinity/Infinity), Ethernet1/0
via 172.16.1.5 (Infinity/Infinity), r, Serial2/0, serno 562
via 10.2.1.3 (Infinity/Infinity), Ethernet1/0, serno 560

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35
Q

How to view traffic share on unequally load balanced EIGRP routes.

A

Traffic share count is in output of ‘show ip route <i>x.x.x.x</i>

36
Q

List EIGRP K values

A 
Bandwidth (K1)
Load (K2)
Delay (K3)
Reliability (K4)
MTU (K5)
37
Q

What is the formula for an EIGRP metric with default K values?

A

Metric = (10^7 / minimum bandwidth) * 256 + (sum of delays) * 256

38
Q

What command sets the EIGRP metric to use only delay in metric calculation

A

metric weights 0 0 0 1 0 0

39
Q

What type of packet renews the EIGRP hold timer?

A

Any EIGRP packet - not just hello…

40
Q

Summarize EIGRP routes

A

interface mode:

ip summary-address eigrp <i>as network subnet</i>

41
Q

What is a discontiguous network?

A

A classful network split apart by a different network.

42
Q

Configure MD5 authentication on an EIGRP interface

A 
hostname R1
!
interface fastEthernet 0/0
 ip address 192.168.12.1 255.255.255.0
 ip authentication mode eigrp 12 md5 
 ip authentication key-chain eigrp 12 MY_KEY_CHAIN
!
router eigrp 12
 network 192.168.12.0
!
key chain MY_KEY_CHAIN
 key 1
  key-string MY_KEY_STRING
43
Q

What are the 2 recommended methods for advertising EIGRP default routes

A

1) redistribute static default route

2) ip summary-address command

44
Q

Configure eigrp hello and hold time

A

interface:
ip hold-time eigrp <i>as seconds</i>
ip hello-interval eigrp <i>as seconds</i>

45
Q

Configure EIGRP summary address

A

ip summary-address eigrp <i>as network mask</i>

46
Q

By default what routes does an EIGRP stub router advertise to backbone routers?

A

connected and summary routes

47
Q

Configure a router as an EIGRP stub router

A

router mode:

eigrp stub

48
Q

When configuring eigrp stub what are the options for routes advertised by the stub?

A

receive-only

connected
static
summary
redistribute

49
Q

What configuration is needed to have an eigrp stub router advertise static routes?

A 
global: 
ip route 1.0.0.0 255.0.0.0 1.2.1.1
router mode:
eigrp stub static
redistribute static
50
Q

EIGRP: filter inbound routes on FastEthernet0/0 so that 172.16.1.0/24 is not learned on that interface

A 
hostname R1
!
interface FastEthernet0/0
 ip address 192.168.12.1 255.255.255.0
!
router eigrp 12
 distribute-list 1 in FastEthernet0/0
 network 192.168.12.0
!
access-list 1 deny   172.16.1.0 0.0.0.255
access-list 1 permit any
51
Q

Use prefix list - allow /28 or larger subnets under 10.10.0.0/16 - distribute in fa0/0 eigrp 12

A

router eigrp 12
distribute-list prefix BRANCHES in FastEthernet0/0
!
ip prefix-list BRANCHES seq 5 permit 10.10.0.0/16 le 28

52
Q

Configure outbound EIGRP route map that filters out 192.168.1.0/24 using an ACL and any prefix under 172.16.0.0/20 with mask /26 or longer using a prefixlit

A 
router eigrp 1
 distribute-list route-map FILTER_OUT out
!
ip access-list standard NET_192
 permit 192.168.1.0 0.0.0.255
!
ip prefix-list SMALL_PREFIXES seq 5 permit 172.16.0.0/20 ge 26
!
route-map FILTER_OUT deny 10
 match ip address NET_192
!
route-map FILTER_OUT deny 20
 match ip address prefix-list SMALL_PREFIXES
!
route-map FILTER_OUT permit 30
53
Q

What command shows frame relay DLCI mapping?

A

show frame-relay map

54
Q

What commands shows if a PVC is active?

A

show frame-relay pvc

55
Q

If not using sub-interfaces what two things are needed to enable spoke-to-spoke communication with EIGRP

A

interface configuration mode:
no ip split-horizon eigrp <i>as</i>
frame-relay map ip <i>spoke-ip hub-dlci</i>

56
Q

Configure frame-relay point-to-point subinterfaces

A 
interface Serial 0/0.12 point-to-point 
 ip address 192.168.12.1 255.255.255.0
 frame-relay interface-dlci 102
!
interface Serial 0/0.13 point-to-point 
 ip address 192.168.13.1 255.255.255.0
 frame-relay interface-dlci 103
57
Q

How does the eigrp ip bandwidth-percent command on a multipoint network.

A

It takes the bandwidth defined on the interface and divides it by the number of neighbors. The percentage is then applied to the result to determine the maximum bandwidth for all neighbors.

58
Q

So that the eigrp ip bandwidth-percent command works properly what is the appropriate bandwidth setting on a multipoint interface?

A

The bandwidth of the smallest PVC multiplied by the number of links.

59
Q

GIven a scenario in which there are 10 sub-interfaces with 64k CIRs and a 256k physical interface that already has the correct bandwidth statement what is the eigrp ip bandwidth-percent statement that should go on each subinterface to allow eigrp to use approximately 32k.

A

ip bandwidth-percent eigrp 1 128

256 / 10 = 25
25 * 1.28 = 32

60
Q

Will two routers with the same EIGRP router ID form a neighbor adjacency?

A

Yes

61
Q

In what case will the EIGRP router ID need to be different.

A

If a router receives an external route from a neighbor that has the same router id it won’t accept it.

62
Q

If an EIGRP external route is dropped due to it being learned from a router with the same router-id what command will you see that happening in.

A

show ip eigrp events

63
Q

Configure EIGRP in named mode for AS 12 using MY_CHAIN for authentication.

A 
router eigrp MY_NAME
 !
 address-family ipv4 unicast autonomous-system 12
  !
  af-interface GigabitEthernet0/0
   authentication mode md5
   authentication key-chain MY_CHAIN
  exit-af-interface
  !
  topology base
  exit-af-topology
  network 192.168.12.0
 exit-address-family
64
Q

List fields in an OSPF hello packet

A 
Router ID
Hello/Dead Interval
Neighbors
Area ID
Router Priority
DR and BDR IP address
Authentication password
Stub area flag
65
Q

How many equal cost paths in OSPF

A 
4 in routing table
16 max (in topology?)
66
Q

OSPF - what is checked before adding LSA information to LSDB? In what cases is it not added and what happens?

A

If entry is not in LSDB it is added.
If it is already in the LSDB and the sequence number is the same it is ignored. If the sequence number is higher it is also added. If the sequence number is lower then an LSU is sent to the source with the newer information.

67
Q

OSPF - what happens when an LSA is added to the LSDB?

A

The router sends an LSAck, floods the LSA, and runs SPF.

68
Q

How long is an OSPF LSA valid for?

A

30 minutes by default

69
Q

What happens when an OSPF LSA expires?

A

The router that sends it will send a new one with a higher sequence number. If it isn’t replaced a router will delete the LSA when the timer expires.

70
Q

Is anything else checked besides sequence number to determine if an LSA is more recent?

A

LSA is added if it has

1) a higher sequence number
2) a higher checksum
3) an age equal to the maximum age
4) if the link-state age is much younger

71
Q

How can one check the sequence number on OSPF LSAs?

A

show ip ospf database

72
Q

Configure ospf plain-text authentication

A

interface configuration mode:
ip ospf authentication
ip ospf authentication-key MYPASS

Alternatively enable authentication on area - just must still set key on interface:

router ospf 1
area 0 authentication

73
Q

Commands needed for ospf md5 authentication

A 
interface FastEthernet0/0
 ip ospf message-digest-key 1 md5 MYPASS
 ip ospf authentication message-digest
!
(instead of ip ospf message-digest-key on interface)
router ospf 1
 area 0 authentication message-digest
74
Q

List all LSA types

A

LSA Type 1: Router LSA
LSA Type 2: Network LSA
LSA Type 3: Summary LSA
LSA Type 4: Summary ASBR LSA
LSA Type 5: Autonomous system external LSA
LSA Type 7: Not-so-stubby area (External) LSA
LSA Type 8: External attribute LSA for BGP

75
Q

What basic information is in an OSPF router LSA?

A

IP prefix on interface

For each link:
Link type
Link ID

76
Q

What are the 4 link types for OSPF LSAs and what is the link id for each?

A

1, Point-to-point connection to another router, Neighbor router ID
2, Connection to transit network, IP address of DR
3, Connection to stub network, IP Network
4, Virtual Link, Neighbor router ID

77
Q

When are OSPF type 2 LSAs generated?

A

By a DR on a multi-access network.

78
Q

On type 4 and 5 LSAs how is auto-summarization performed.

A

It isn’t.
Type 4 is to find the ASBR
Type 5 is the prefix

79
Q

How is the OSPF router-id selected? How can it be statically defined?

A

Manual configuration of the router ID.
Highest IP address on a loopback interface.
Highest IP address on a non-loopback interface.

R1(config)#router ospf 1
R1(config-router)#router-id 111.111.111.111

80
Q

Where does one configure a passive interface for OSPF?

A

Router configuration mode.

81
Q

Configure an ospf priority that will give priority over a Cisco router with default priority.

A

interface fastEthernet0/0

ip ospf priority 2

82
Q

If you set the OSPF priority to be highest on the segment what routers need their OSPF processes cleared in order to get it to take effect?

A

The DR and BDR are the only 2 routers that need to be cleared with clear ip ospf process.

83
Q

If OSPF priority is the same which router becomes DR in multi-access segment?

A

Highest router-id

84
Q

What is the command to set the ospf reference bandwidth to 1 Gbps?

A

Router(config-router)#auto-cost reference-bandwidth 1000

85
Q

What is the command to get OSPF to advertise a default route?

A

router mode:
default-information originate (always)

Without always keyword it will only be originated if there is a default route already in the routing table on that router.

86
Q

What are the basic things to configure for an OSPF NBMA network?

A

interface config
ip ospf non-broadcast
ip ospf priority 0 (on spokes)
ip ospf priority 1 (on hub)

 On hub:
 router mode:
  neighbor spoke 1
  neighbor spoke 2 
  ... etc ...

Computer Networking (3 decks)

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