Routing Protocols Flashcards
RIP metric, classful or classless, how advertised, and AD
Hop count, Distance vector, v1 classful/v2 classless, 120
IGRP metric, classful or classless, how advertised, and AD
Bandwidth and Delay, classful, Distance vector, 100
EIGRP metric, classful or classless, how advertised, and AD
Bw and delay, classless, hybrid, 90 or 170
OSPF metric, classful or classless, how advertised, and AD
Link state, classless, cost bw, 110
IS-IS metric, classful or classless, how advertised, and AD
Link state, classless, cost 10, 115
BGP metric, classful or classless, how advertised, and AD
Path vector, classless, many path attrib, 20 and 200
Interior gatway protocol examples
EIGRP, IS-IS (ISP typically), OSPF, RIP
External gateway protocol examples
BGP
Distance vector protocol examples
EIGRP and RIPv2
Link-State Protocol examples
OSPF and IS-IS
Exchanges info about the whole topology. Each router determines the best paths on its own, using SPF.
Link-state protocols
Exchanges routes as vectors of distance and direction. Distance=metric of links or hop count, Direction=next-hop neighbor
Distance vector protocols
Exchanges routes as the vector of path and direction. Path = list of different path attributes, Direction=next-hop neighbor
Path vector protocols
Address assigned to an interface on more than 1 node. When packet is sent, it is routed to the nearest interface that has the address.
Anycast
Local broadcast address
255.255.255.255
Last IP address in the subnet
Directed broadcast address
224.0.0.0 to 239.255.255.255
Reserved ipv4 multicast address
224.0.0.5 and 224.0.0.6
Multicast OSPFv2
224.0.0.9
RIPv2 multicast
224.0.0.10
EIGRP multicast
FF02:5 and FF02:6
Multicast OSPFv3
FF02:9
RIPng multicast
FF02:A
EIGRP multicast
2000::/3
Global IPv6 addresses
FE80::/10
Link-local addresses
FF00::/8
Multicast addresses
FC00:7
Unique local addresses
::1
Loopback
Example of a broadcast network
Ethernet
A network that can support many routers but does not have broadcast ability
NBMA network (e.g. Frame relay and ATM)
Point-to-Point technology that allows the transport of any layer 2 protocol at the PE
VPWS (Virtual private wire service)
Emulates an Ethernet multiaccess LAN segment over the MPLS core and provides multipoint-to-multipoint service
VPLS (Virtual private lan service)
3 main components of a GRE tunnel
(1) Passenger protocol (IPv4, IPv6)
(2) Carrier Protocol (GRE)
(3) Transport Protocol (IP)
GRE creates this many bytes of additional overhead
24
This technology enables a single GRE interface to support multiple GRE tunnels and simplifies the complexity of the configuration.
mGRE
DMPVPN relies on what 3 things
mGRE, NHRP, IPsec
Routing protocol: If a network is 16 or more hops away, the router considers it unreachable.
RIP
udp port 520
RIP IPv4
udp port 521
RIP IPv6
Routing protocol: Subnet mask is not exchanged during the update process.
RIPv1
AD of RIP
120
Routing updates every 30 seconds and with topology change
RIP
Operates within an autonomous system
IGP
Operates between autonomous systems
EGP
Each router determines the best path on its own
distance vector protocol
Exchanges only the best routes with its neighbors
Link-state protocol
3 Benefits of route summarization: A. smaller routing table B. lower use of IP addresses C. more accurate path selection D. fewer routing updates E. Improved convergence
ADE
Which one of these four RIPng configuration steps can you leave out but still have RIPng up and running at the end? A. enable IPv6 routing B. create a RIPng routing process C. enable IPv6 on the interface D. enable RIPng on the interface
B
EIGRP protocol number
88
Metric calculation for EIGRP
Advertised metric + link cost
EIGRP packets
Hello, ACK, Update,
Routing protocol: Uses RTP for reliable, guaranteed delivery of packets.
EIGRP
Uses DUAL (Diffusing Update Algorithm) to calculate the best routes to remote networks.
EIGRP
T/F: Metric is not used for the EIGRP metric calculation. except in tie-breaker cases.
True, but MTU is exchanged in routing updates.
EIGRP: Another word for metric weights
K-Value..default is 0
The EIGRP delay value is the sum of the delays in the math, in _______, while the show interface output displays the delay in ______.
tens of microseconds/microseconds
_____ means that reported distance must be less than feasible distance and is critical to maintain loop-free topology.
Feasibility condition
Routers configured as ____ do not forward EIGRP learned routes to other neighbors.
Stubs
EIGRP: Without a feasible successor, ,when successor goes down, a ____ must be sent.
Query
Nonstub routers will/will not send query messages to stub routers?
will not
Command to change a router to stub for EIGRP
router eigrp 1
eigrp stub
If a router does not receive a reply to all the outstanding EIGRP queries within three minutes (the default time), the route goes into the ____ state
SIA
EIGRP: Once the ____ timer expires, the neighbor relationship is reset.
active
EIGRP: If the router receives enough packets to maintain the neighbor relationship, but is not receiving all the queries or replies, the affected devices will generate what error messages?
EIGRP DUAL-3-SIA error messages
When no reply to a query is received, EIGRP sends a ____ packet when the active timer is halfway through, after 90 seconds.
SIA-Query
EIGRP summarization limits ______ and improves ______
query scope/convergence
Command for manual summarization EIGRP
ip summary-address eigrp
Default value for EIGRP variance? Max value?
1 (default) / 128 (max)
The only way to summarize IPv6-advertised prefixes in EIGRP is ____
manual summarization
EIGRP: If you don’t assign a router ID, what happens?
the router will automatically assign it the highest loopback or the highest active interface IPv4 address. IPv6 requires a router ID.
EIGRP for IPv6 uses assigned dedicated multicast address what? how about IPv4?
FF02::A / 224.0.0.10
____ EIGRP configuration tries to eliminate configuration complexity that occurs when configuring EIGRP for both IPv4 and IPv6.
Named
Within the EIGRP address family, what is the command to enter address family interface configuration mode?
af-interface
What is the formula for selecting a feasible successor?
A. The AD of the current successor route is less than the FD of the feasible successor route.
B. The FD of the current successor route is less than the AD of the feasible successor route.
C. The FD of the feasible successor route is less than the AD of the current successor route.
D. The AD of the feasible successor route is less than the FD of the current successor route.
D
What does the passive state in the EIGRP topology table signify?
A. There are outstanding queries for this network.
B. The network is unreachable.
C. The network is up and operational, and conditions are normal.
D. A feasible successor has been selected.
C
____ propagates link-state advertisements rather than routing table updates.
OSPF
Requirements for an OSPF neighbor to establish. (4)
- Area has to match
- Hello/Dead timers have to match
- Stub flag must match
- Authentication must match
OSPF: discovers neighbors and builds adjacencies between them.
Hello
OSPF: Checks for database synchronization between routers. Packet describes the LSDB.
DBD
OSPF: Requests specific LSAs from another router that are missing in its table.
LSR(equest)
OSPF: Sends specifically requested LSAs. Are the flooded responses from LSR packets.
LSU(pdate)
To calculate the best path, OSPF uses ___ or ____
SPF or Dijkstra’s algorithm
OSPF protocol number
89
T/F: OSPF uses broadcast, rather than multicast or unicast
F. OSPF uses multicast or unicast
OSPF multicast address
224.0.0.5 for OSPF routers and 224.0.0.6 for DR and BDR routers
T/F: OSPF can do auto summarization.
F: OSPF does manual only.
What authentication for OSPF?
cleartext, MD5, and SHA
OSPF area 0 is also known as ___
backbone area or transit area
OSPF: end users are not found within ____
backbone area/area 0
OSPF: A backbone area connects to all other ___.
nonbackbone areas
A router that has interfaces connected to at least 2 different OSPF areas, including the backbone area.
ABR
A router that has at least one of its interfaces connected to an OSPF area and at least one of its interfaces connected to an external non-OSPF domain.
ASBR
A router that has all its interfaces connected to only one OSPF area
Internal router
OSPF: A router that has at least one interface connected to the backbone area.
Backbone router
OSPF: Acknowledges the other packet types.
LSA(ck)
OSPF: LSA Type Router announces its presence. Only within the area
1
OSPF: LSA Type Networks are broadcast. Only within the area by the DR.
2
OSPF: LSA Type Summary. An ABR sends the summaries out to other areas
3
OSPF: LSA Type External. Generated by ASBR. Details imported from another routing process. Get flooded everywhere except special areas.
5
OSPF. When the router sees its own router ID int he hello packet received from the neighbor, it wil transit to the ___ state.
2-WAY
OSPF: When a router receives a hello from the neighbor but has not yet seen its own router ID in the neighbor hello packet, it will transit to the ____ state.
INIT
OSPF: In the DBD exchange process, the router with the highest ____ will become master and it will be the only router that can increment sequence numbers.
router id
OSPF: After master/slave selection is complete, the database exchange can start, and this state is called ____.
ExChange
OSPF: After the database exchange is complete, the next state is ____ where LSRs are exchanged.
Loading
OSPF: LSA Type ASBR-Summary. Detailed next-hop information is flooded to all routers in the OSPF domain regarding how to get to the ASBR.
4
The OSPF hello packet contains three specific fields used for DR/BDR election. What are they?
Designated router, backup designated router, and router priority
OSPF: On multiaccess broadcast networks, routers use multicast destination address ______ to communicate with the DR and the DR uses ____ to communicate with all other non-DR routers. On NBMA networks, the DR and adjacent routers communicate using ____
224.0.0.6 / 224.0.0.5 / Unicast
OSPF: The name of a router that is not a DR or BDR
DROTHER
OSPF: The router with the highest ___ becomes the DR.
priority
OSPF: If the priority values are equal, the router with the highest ____ becomes the DR.
router ID
OSPF: If a router is set with priority of 0, what is its role in the DR/BDR election.
It does not participate.
OSPF neighbors with mismatched MTUs are stuck in the _____ adjacency state. MTUs must match.
EXSTART
The default OSPF hello timers on multiaccess and P2P links is __ seconds while all other network types, including NBMA, is ___ seconds.
10 / 30
The default value of the dead interval for OSPF is ____
4 times the hello interval.
OSPF state: no active neighbor detected
Down
OSPF state: hello packet received. bi-directional communication not yet started
INIT
OSPF state: Own router ID received hello. at the end of this stage, DR and BDR election will occur.
2-WAY
OSPF state: Master and slave roles determined
EXSTART
OSPF state: Database description packets (LSDB) sent
EXCHANGE
OSPF state: Exchange of LSRs and LSUs
LOADING
OSPF state: Neighbors fully adjacent
FULL
There is no DR/BDR election on what type of network
Point-to-Point and Point-to-Multipoint
This network type is used on networks that interconnect more than 2 routers but without broadcast capability
Nonbroadcast (NBMA)
This type of network has the same characteristics as point-to-multipoint, except that neighbors are not discovered dynamically.
Point-to-multipoint nonbroadcast
You can change the OSPF network type with what command?
ip ospf network
OSPF: The link-state ID of the type 1 LSA is the ____
originating router id
OSPF: The link-state ID of the type 2 LSA is the ____
IP interface address of the DR
OSPF: The link-state ID of the type 3 LSA is the ____
destination network number
OSPF: The link-state ID of the type 4 LSA includes the ____
router ID of the described ASBR
OSPF: The link-state ID of the type 5 LSA is the ____
External Network Number
Specialized LSA type that are used in multicast OSPF applications
6
OSPF LSA type used in special area type NSSA for external routes.
7
LSA types used in OSPFv3 for link-local addresses and intra-area prefixes. (hint: 2 answers)
8 and 9
Generic LSA types, also called opaque, which allow future extensions of OSPF. (hint: 2 answers)
10 and 11
OSPF LSA types that are flooded within an area
1 and 2
OSPF LSA types that are flooded when exchanging information between the backbone and standard areas.
3 and 5
OSPF LSA type that are injected into by the ABR because all routers in the OSPF domain need to reach the ASBR.
4
With each OSPF network change, an updated LSA is generated with the link-state age set to ____
0
OSPF periodically refreshes each LSA after the link-state age timer reaches ____
30 minutes
OSPF: In a normal operating network, you will not see the age variable with a value higher than ____
1800 seconds or 30 minutes
You can verify how often the SPF algorithm was executed using what command?
show ip ospf
What is the OSPF cost formula?
cost = reference bandwidth / interface bandwidth
What is the default reference bandwidth in OSPF?
100 mbps
What command do you use to change the OSPF reference bandwidth?
router ospf 1
auto-cost reference-bandwidth
What command do you use to change the OSPF cost on a serial link?
interface serial 2/0
ip ospf cost
OSPF: ____ are designed to reduce the amount of flooding, the LSDB size, and the routing table size in routers within the area.
Stub areas and route summarization
OSPF command to summarize a route in an area.
router ospf 1
area range
OSPF: inter-area routes summarized have a metric equal to the ____ of all subnets within the summary address range and will have a route to ____ to avoid loops and is generated if at least ____ within the area falls in the summary address range.
lowest cost / null 0 / one subnet
OSPF command to summarize an external route.
router ospf 1
summary-address
OSPF: Default routes are injected using what type of LSA
5
OSPF: A ___ is a special area type that does not accept information about routes that are external to the AS and all type 5s are dropped.
Stub area
OSPF: In a stub area, the stub ABR advertises a default route using what type of LSA
3
OSPF: A ____ area does not accept external or interarea routes and is Cisco proprietary. It blocks LSA type 3 and 5.
totally stubby
OSPF: Command to configure a totally stubby area on ABR
router ospf
area 2 stub no-summary
OSPF: When you use the ___ or the ____ command to redistribute routes into an OSPF routing domain, the router automatically becomes an ASBR
Redistribute / default-information
OSPF: An ____ metric-type keeps the same metric (external) all through transit.
E2
OSPF: An ____metric-type increments the metric (external and internal) throughout transit.
E1
OSPF: 4 command options for “default-information originate”
always, metric, metric-type, route-map
OSPF: The ____ is a nonproprietary extension of the existing stub area feature that allows the injection of external routes in a limited fashion into the stub area
NSSA
OSPF: Command to configure an NSSA area
area 1 nssa
area 1 nssa no-summary
OSPF: This type of stub area blocks type 3, 4, and 5 LSAs from ABR and blocks type 3 and 5 LSAs from ABR. Cisco proprietary.
Totally NSSA
OSPF: This type of stub area accepts type 7 LSA, later converts it to type 5, accepts type 3, and blocks type 4 and 5 from ABR. Non-proprietary.
NSSA
OSPF: LSA type that can only exit in an NSSA. Has propagate bit in header to prevent propagation loops.
7
OSPF: This type of LSA has local-link flooding scope.
8
OSPF: Type of LSA that contains intra-area prefix LSAs for each router or transit network
9
To control the maximum number of equal-cost routes a process for OSPFv3 routing can support, use the ____ command in IPv6 or IPv4 address family configuration mode. The range is ___ to ____.
maximum-paths / 1 to 64
New style OSPFv3 for IPv4 and IPv6 command.
router ospfv3
Traditiona OSPFv3 command
ipv6 router ospf
What is the OSPF transport? A. IP/88 B. TCP/179 C. IP/89 D. IP/86 E. UDP/520
C.
An ABR maintains ______
A. a single DB for all areas
B. A separate database for each area with which it is connected
C. 2 DB; one for the backbone and one for all other areas.
D. A separate routing table for each area
B
Which 2 methods does OSPF employ to conserve the competing resources? A. area-based segregation B. LSDB C. passive interfaces D. redistribution E. network types
A, C
What are 2 reasons why route summarization is important?
A. it reduced LSA type 1 flooding
B. it reduces LSA type 3 flooding
C. it reduces the size of the routing table
D. it reduces the size of the neighbor table
B, C
Route summarization reduces the flooding of which 2 of the following LSA types? A. router B. network C. Summary D. External E. NSSA
C, D
Stub area design can improve \_\_\_\_. A. CPU utilization on routers in the stub B. the number of adjacencies in the stub C. the ability to reach outside networks D. LSDB size on routers in the backbone
A
What address would you configure in the neighbor command to set up an OSPFv3 adjacency over an NBMA link? A. local IPv4 address B. neighbor IPv4 address C. interface link local IPv6 address D. local global IPv6 address E. neighbor link-local IPv6 address F. neighbor global IPv6 address
E
EIGRP default-metric command has numbers in which order? (e.g. default-metric 1000 100 250 100 1500
Bandwidth, delay, rely, load, mtu
OSPF type of route where the external cost is added to the internal cost of each link that the packet crosses. Use this for best path.
O E1
OSPF type of route where the external cost is the external cost only. Used if only one ASBR is advertising an external route to the AS. Use with load balancing.
O E2
OSPF: One of the ways to control routing updates is a technique called a ___.
Distribute List
OSPF distribute list consists of an ___ telling which routes are permitted and then the ____ command to assign it to the ospf process.
access list/distribute-list 7 out/in eigrp 100
The intended use of ____ is limited to route filtering, where access lists were originally intended to be used for packet filtering and were then extended to route filtering.
prefix lists
Prefix list command example
ip prefix-list permit/deny /
____ are complex access lists that allow conditions to be tested against a packet or route using the match commands. If conditions match, actions can be taken to modify attributes of the packet or route. These actions are specified by the set commands.
Route maps
There is always an implicit deny at the end of an access list or ____.
Route map
In a route map, match criteria in the same line are processed with a logical ___
OR
In a route map, match criteria separated vertically vertically under a route map line uses a logical ___
AND
To change the AD for EIGRP, the command is what?
distance
To change the AD for OSPF, the command is what?
distance ospf intra-area inter-area external
____ are simple labels that are attached to selected routes and are used by route maps to set and match.
Route Tags
The 3 key issues of redistribution are what?
Routing loops, Incompatible routing information, inconsistent convergence time
Which matching method cannot be used with a prefix list filter? A. mask filtering B. using ge C. using le D. using le and ge E. packet length
E
Which four tools can be used in route filtering? A. access lists B. prefix lists C. summarization D. distribute lists E. QoS F. route maps
A, B, D, F
What does the redistribute eigrp 100 subnets metric-type 1 command do when used in router configuration mode under OSPF process 1?
A. redistributes from EIGRP AS 100 into OSPF and changes metric type from type 2 to type 1
B. redistributes from EIGRP AS 100 into OSPF process 1 and changes the metric value of each subnet
C. redistributes only from EIGRP AS 100 subnets of metric type 1
D. redistributes from EIGRP and processes the first 100 subnet of metric type 1.
A
Cisco switching mechanisms: slowest method - every packets examined by CPU; all forwarding decisions made in software
Process switching
Cisco switching mechanisms: faster method - first packet in each flow examined by CPU; forwarding decision cached in hardware for subsequent packets in flow
Fast switching
Cisco switching mechanisms: fastest method - hardware forwarding table is created regardless of traffic flows; all packets switched using hardware. Default switching mode
CEF
CEF is enabled by default in ____, but not ___
IPv4/IPv6
Command to turn off CED
no ip route-cache cef
___ provides solutions for routing where legal, contractual, or political constraints dictate that traffic be routed through specific paths. It bypasses the routing table.
PBR (policy-based routing)
Command to apply a PBR to an interface.
ip policy route-map
show ip policy
_____ actively send data across the network to measure performance between multiple network locations or across multiple network paths. They use time-stamp information to calculate performance metric, such as jitter, latency, network and server response times, packet loss, and mean opinion score.
Cisco IOS IP SLAs
Commands to setup an SLA that pings and interface 10 times forever.
ip sla
icmp-echo x.x.x.x source-interface eth0
frequency 10
ip sla schedule start-time now life forever
Command to setup a track on an SLA
track 1 ip sla reachability
If an SLA determines a link to be alive, what command would assign the proper default routing.
ip route 0.0.0.0 0.0.0.0 track
What is the command to assign SLA with PBR for dynamic path control?
set ip next-hop verify-availability track
In fast switching, when some destination is already cached, is an additional ARP request necessary?
A. Yes
B. No
B
Which three of these options cannot be CEF-switched and must be processed in software?
A. packets with IP header options
B. packets received with a larger MTU than that of an output interface, and therefore must be fragmented.
C. packets that need NAT
D. packets that are forwarded to a tunnel interface
E. packets with a source address that is not in the FIB table.
A, B, D
PBR can be used to optimize the traffic path for some specific application. True or false?
A. True
B. False
A
PBR by itself can be used to dynamically alter the traffic path, depending on network performance.
A. True
B. False
B
Examine the PBR and IP SLA configuration snippet given below. What happens to a packet when the status of the tracked object is “down”?
set ip next-hop verify-availability 10.1.1.1 10 track 1
A. The packet is dropped and an ICMP “destination-unreachable” message is returned to the sender.
B. The packet is just dropped.
C. The packet is forwarded using a routing table.
D. The packet is processed with the next route-map statement.
C
Type of ISP connectivity where a company uses only one service provider, and there is no redundancy.
Single-homed
Type of ISP connectivity where 1 ISP is used, but 2 links to that ISP are used.
Dual-homed
Type of ISP connectivity where the customers is connected to multiple ISPs using 1 link to each.
Multihomed
Type of ISP connectivity where the customer has multiple links to multiple ISPs.
Dual-multihomed
For a multihomed connection PA address space is required. T or F
False. It must be PI (provider independent)
_____ address space is assigned directly to an organization by the RIR (Regional Internet Registry), so the address space is not related to your ISP.
Provider independent
Command to disable learning the default route in DHCP.
no ip dhcp client request router
Type of IP address assigned to a device on an internal network.
Inside local address
IP address of an internal device as it appears to the external network.
Inside global address
IP address of an external device as it appears to an internal network.
Outside local address
IP address assigned to a device on an external network.
Outside global address
___ removes the requirement to configure an interface as either inside or outside.
NAT Virtual Interface (NVI)
NVI is configured in the interfae with which command?
ip nat enable
____ provides the ability to configure IPv6 addressing information on host devices without any intervention from the network administrator.
SLAAC (Stateless autoconfiguration)
___ works in combination with SLAAC, but the DHCP server is pinged for additional info such as DNS and NTP.
Stateless DHCPv6
___ means the IPv6 addressing and additional information is only received from the server by setting the managed-config-flag flag in the route advertisements.
Stateful DHCPv6
____ is an extension to DHCPv6. Its task is to assign whole subnets from a DHCPv6 server to a DHCPv6 client.
DHCPv6-PD
IPv6 ICMP ACL options
nd-ns and nd-na (neighbor discovery, sync and ack)
Command to apply IPv6 ACL to interface
ipv6 traffic-filter in/out
In BGP, neighbors have to be directly connected. T or F?
False. They don’t have to be directly connected
In BGP, the “network” command is what to advertise or enabled on which interface?
what to advertise
