Shared Flashcard Set

Details

CCIE Routing
flash cards for CCIE topics
122
Computer Networking
Professional
04/13/2010

Additional Computer Networking Flashcards

 


 

Cards

Term
What is the default OSPF network type for a Frame-Relay point-to-point interface?
What is the Default Hello interval?
Definition
point-to-point
10 seconds
Term
What is the default OSPF network type for a Frame-Relay point-to-multipoint interface?
What is the Default Hello interval?
Definition
Nonbroadcast
30 seconds
Term
Which OSPF network types require neighbor configuration?
Definition
Nonbroadcast
Point-to-multipoint nonbroadcast
Term
Which OSPF network types have a hello interval of 10 seconds?
Definition
Broadcast
Point-to-point
Term
What OSPF network types elect DR/BDR?
Definition
Broadcast
Nonbroadcast
Term
What is the Administrative Distance for a connected interface?
Definition
0
Term
What is the Administrative Distance for a IPv4 static route that points to an interface?
Definition
1
Term
What is the Administrative Distance for EIGRP summary routes?
Definition
5
Term
What is the Administrative Distance for an external BGP route?
Definition
20
Term
What is the Administrative Distance for an internal EIGRP route?
Definition
90
Term
What is the Administrative Distance for an OSPF route?
Definition
110
Term
What is the Administrative Distance for a RIP route?
Definition
120
Term
What is the Administrative Distance for an external EIGRP route?
Definition
170
Term
What is the Administrative Distance for an internal BGP route?
Definition
200
Term
What is the default percentage of bandwidth that EIGRP can use for updates?
Definition
50 %
Term
What EIGRP messages are acknowledged?
Definition
Updates
Queries
Replies
Term
What are private ASNs used for confederation BGP?
Definition
64512-65535
Term
What is the default OSPF network type for a Frame-Relay physical interface?
What is the Default Hello interval?
Definition
Nonbroadcast
30 seconds
Term
What is the default Hello timer and Dead interval for OSPF on broadcast networks?
Definition
Hello: 10 seconds
Dead: 40 seconds
Term
In what state is the DR elected?
Definition
The Two-Way state.
Term
If AS_PATH = {20 30}, what do we know about this NLRI?
Definition
The "{}" brackets indicate that this route has been aggregated with the command "aggregate address ... as-set". The AS's in the brackets are not ordered.

"aS-Sets lead to Squiggly brackets"
Term
If the AS_PATH looks like this: (65534 54435), what do we know about this prefix?
Definition
The "()" brackets indicate confederation AS numbers.
Term
What type of LSA is sent when "default-information originate" is configured under the OSPF process?
Definition
Type 5. "default-information-originate" makes the router an ASBR
Term

Name three conditions that must be met for a  summary route to be advertised.

Definition

1) Advertised summary is assigned the metric of the lowest-metric component subnet.

2) Router does not advertise summary if no component subnets in the routing table.

3) Summarizing router creates a local route to summary, destination null 0.

Term
What command is used to summarize redistributed routes in OSPF.
Definition
"summary-address"
Term
What command is used to summarize internal OSPF routes at an ABR?
Definition
"area range"
Term
By default, what eigrp routes are advertised TO a stub router?
Definition
By default, all routes are advertised TO a stub.
Term
By default, what routes will a stub EIGRP router advertise?
Definition
Summary and connected.
"EIGRP stubs are Sum-what Connected"
Term
What types of authentication does EIGRP support?
Definition
MD5 only.
Term
What is the default metric for EIGRP?
Definition
256 (delay + 10^7/BW)
Where bandwidth is the lowest bandwidth in the path, and delay is cumulative.
Term
What are the metric weights from k1 to k5?
Definition
k1 = bandwidth = 1
k2 = load = 0
k3 = delay = 1
k4 = reliability = 0
k5 = mtu = 0

"Blind Ladies Don't Route Much"
Term
What must be true for EIGRP to advertise a default route using the "ip default-network x.x.x.x" command?
Definition
1) The network must be classful
2) The classful network must be in routing table
3) EIGRP must be advertising the classful network.
Term
Name three ways of limiting query scope in EIGRP.
Definition
1) use stubs (queries not sent to stub)
2) summarize (routers will reply immediately if they only have summary)
3) filter with distribute lists (routers will reply immediately if they don't have the subnet
Term
What must work for EIGRP neighbors to form?
Definition
1) Authentication passes
2) AS must be same
3) source IP address must be in router's primary connected subnet.
4) k values must match
Term
What is OSPF's IP protocol number?
Definition
89
Term
What port does RIP use?
Definition
UDP 512 = RIP
Term
What is the EIGRP multicast address?
Definition
224.0.0.10
Term
How often are EIGRP Hellos sent?
Definition
Every 5 seconds on fast links, 60 on slow links.
Term
What are the hello timers for EIGRP on Frame Relay point-to-point, multipoint and main interfaces?
Definition
5 for point to point
60 for multipoint and main interface
Term
What is EIGRP hold time?
Definition
3 x the Hello time
Term
What happens if EIGRP neighbors don't have matching hello and hold times?
Definition
They become neighbors anyway. EIGRP neighbors don't have to have matching hello and hold timers.
Term
Where is the following configured:
ip authentication mode eigrp 1 md5
ip authentication key-chain eigrp 1 MYCHAIN
Definition
EIGRP enables authentication on the interface.
Term
Why would you use "traffic-share min across-interfaces" in EIGRP?
Definition
To only send traffic on minimum cost route but install all unequal-cost routes in the routing table for faster convergence.
Term
What do you need to do to prevent core routes from being advertised to stub router?
Definition
Install a summary route on the outbound interface of the core router (which suppresses all more specific routes). Declaring a router stub is not enough to prevent routes from being advertised into it.
Term
If a new router appears with a higher priority in an OSPF broadcast network, what will happen?
Definition
Nothing. Current active DR and BDR are not pre-empted
Term
What is the purpose of the DR in OSPF?
Definition
Manage LSA flooding.
Term
What is the OSFP cost formula?
Definition
Cost = reference bandwidth / bandwidth
Term
What is the default OSPF reference bandwidth?
Definition
100 Mbps
Term
What is the OSPF cost of a FE link if the reference bandwidth is default?
Definition
cost = ref / BW = 100 Mbps/ 100 Mbps= 1
Term
What is the cost of an Fast E link and a gigE link with the following configured?
ospf auto-cost reference bandwidth 5000
Definition
FE cost = 50
GE cost = 5

(auto-cost reference bandwidth is in Mbps)
Term
When a DR is used, what state do non-DR/BDR neighbors stop at in the OSPF state machine?
Definition
The Two-way state. The routers will continue with the rest of the state machine with DR and BDR routers.
Term
What happens in the OSPF exstart state?
Definition
router and DR determine who will be the master and establish sequence number for DDP exchange.
Term
What OSPF packet contains LSA headers?
Definition
Database Description Packet
Term
When are DDP packets exchange in the OSPF state machine?
Definition
Routers exchange DDPs in the exchange state.
Term
What happens during the Loading state in OSPF?
Definition
Router sends LSR for any LSAs that it does not have (LSA headers were sent earlier in DDPs). Other router responds with LSU.
Term
What does the Full State represent in OSPF?
Definition
Router has LSDB as every other router and can run Dijkstra.
Term
What three packets are used for building OSPF adjacencies?
Definition
DDP, LSR, LSU
Term
What feature allows routers to collect a group of LSAs and send the group in an LSU? What is the default value of this feature?
Definition
Group pacing configured with "timers lsa-group-pacing" Default is 4 minutes.
Term
What does "ip ospf flood-reduction" do?
Definition
Sends LSA with the DoNotAge bit set (so router will not need to reflood LSA every MaxAge (30 minutes).
Term
If multiple routes exist and the inter-area route costs less than the intra-area route, which one will OSPF use?
Definition

The higher cost intra-area one.

 

OSPF will always choose routes in this order (regardless of cost):

intra-area

inter-area

External Type 1

External Type 2

Term
What's in a Type 1 LSA, who sends it and in what area?
Definition
Type 1 is a Router LSA sent by every router, containing all links, state and cost. Router LSAs are flooded in the area in which they originated.
Term
What LSA type is produce by a DR and contains a list of all attached router? Where is this LSA flooded?
Definition
Type 2 Network LSA is produce by DR and flooded in originating area.
Term
What are Type 3 LSAs and who sends them?
Definition
ABRs produce Type 3 Network Summary LSAs, summarizing Type 1 and 2 LSAs for forwarding into another area.
Term
What does an ABR do with Network Summary LSAs from another ABR in a non-backbone area when calculating least-cost path?
Definition
Ignores them.
Term
Who creates an ASBR Summary LSA and what type is it?
Definition
ABRs create Type 4 ABSR Summary LSAs when flooding Type 5 LSAs to another area (lists ABR cost to ASBR).
Term
What two LSAs are originated by ASBRs and where are they flooded?
Definition
Type 5 AS External LSA -- flooded through entire AS
Type 7 NSSA External LSA -- flooding through NSSA only
Term
Where are Type 5 LSAs flooded and what do they describe?
Definition
Type 5 AS External LSAs are flooded by ASBRs through the entire AS to advertise external routes.
Term
What does a forwarding address of 0.0.0.0 mean in a Type 5 or Type 7 LSA?
Definition
Forwarding address 0.0.0.0 means that the interface from OSPF to external router is not being advertised by ASBF (through interface command).
Term
What area has Type 1,2 and 3 LSAs?
Definition
Stub area has 1,2,3 only. Types 4 and 5 are blocked.
Term
What area allows Type 1, Type 2 and summary-only Type 3 LSAs?
Definition
Totally stubby areas.
Term

What does an ABR do when receiving a Type 7 NSSA LSA?

Definition

If P bit is 1, ABR translates Type 7 to Type 5 and floods (NSSA ASBR will not be advertised by Type 4 LSA because the ABR originate the Type 5 LSA)

 

If P bit is 0, type 7 LSA will not be advertised outside the area.

Term
What does the "not-advertise" option in the "summary-address" OSPF CLI do?
Definition
Allows the NSSA router to set the P-bit to 0 (so ABR will not flood this LSA to other areas).
Term
What is the order of preference if multiple types of OSPF routes exist to a destination?
Definition
1) Intra-area (regardless of cost!) 2) Inter-area 3) Type 1 External 4) Type 2 External
Term
What is the Type 1 external cost to an ASBR in the same area?
Definition
Cost = cost to ASBR + external cost
Term
What is the Type 1 External cost when the ASBR is in a different area?
Definition
cost = cost to ABR + ABR cost to ASBR + external cost
Term
What is the Type 2 External cost to a destination outside the the AS?
Definition
External cost only (does not include cost to ASBR or ABR)
Term
What configuration command would make OSPF area 1 totally stubby?
Definition
"area 1 stub no-summary"
Term
What CLI would make area 1 not so stubby?
Definition
area 1 nssa
Term
What types of LSAs are allowed in area 192 below?
area 192 nssa no-summary
Definition
Type 1,2 and summary only Type 3. Type 7 LSAs from ASBRs within area would be flooded also.
Term
Which LSAs are allowed in area 192 if configured on a router that is both ABR and ASBR?
network 192 nssa no-redistribution no-summary
Definition
Type 1, 2 and summary only Type 3. (No-redistribution suppresses Type 7 LSAs from this router, no-summary suppresses Type 3 and Type 4)
Term
What configuration would enable an NSSA ABR to advertise Type 3 and 4 LSAs but not Type 5 and 7 (except for a Type 7 default route)?
Definition
area 192 nssa no-redistribution default-information-originate
Term
What configuration would enable an NSSA ABR to advertise Type 3 and 4 LSAs but not Type 5 and 7 (except for a Type 7 default route)?
Definition
area 192 nssa no-redistribution default-information-originate
Term
Where is authentication configured in ospf?
Definition
authentication is enabled in global config, can be overridden with interface config
Term
What kinds of authentication does OSPF support?
Definition
OSPF -- plaintext and md5
Term
What command enables you to suppress hellos and LSAs after initial sync? What areas is this supported on?
Definition
"ip ospf demand-circuit"
Use only on stub networks. Sets DC-bit and DoNotAge bit.
Term
What does the following command do and what kind of router is it configured on?
router ospf 1
area 15 range 10.0.0.0 255.248.0.0
Definition
area 15 range 10.0.0.0 255.248.0.0

Configured on an ABR, this command summarizes area 15's subnets into all other areas.
Term
On what type of router is the following configured and what does it do?
router ospf 1
summary-address 172.26.0.0 255.255.0.0
Definition
summary-address 172.26.0.0 255.255.0.0

configured on ASBR (only ASBRs can summarize external routes)
Term
How do you redistribute a default route in OSPF?
Definition
OSPF does not distribute default routes, even with redistribution. Need to include "default-information originate"
Term
If "default-information originate" is configured in OSPF, what type of LSA is generated?
Definition
Type 5 (Type 7 for NSSA) with cost 1 type E2.
Term
What happens during OSPF graceful restart?
Definition
FIB forwards packets while RIB is restarted.
Term
Name five methods that allow redistribution between different OSPF processes. Of these, which allow one domain to backup the other? Of these, which allow backup in the presence of other ASBRs with valid external routes?
Definition

1) distance 255 (other router)

2) tag-based filtering

3) redistribution with match internal

4) prefix-based filtering 

5) prefix-based filtering with prefix-based administrative distance.

 

3) - 5) allow backup.

 

only 5) allows backup with external routes

Term
By default, frame relay multipoint interfaces are what OSPF network type?
Definition
NBMA

Use "ip ospf network point-to-multipoint" interface config to change this.
Term
What is BFD?
Definition
Bidirectional Forwarding Detection -- a protocol that detects liveliness like an IGP, except at a more accelerated rate. Independent of the IGP, it informs IGP of problems (IGP must take action).

Works for OSPF, ISIS, EIGRP and BGP
Term
What are the advantages of BFD over modified hello mechanisms in OSPF, EIGRP, ISIS?
Definition
  • BFD is more data-plane, so less process intensive than frequent Hellos.
  • BFD detection is subsecond (others are 1 - 2 seconds with minimum timers)
  • BFD is independent of routing protocol.
Term
what determines who wins OSPF DR election?
Definition
Highest priority
Highest RID
Term
For which routing protocols do hold and hello timers have to match for routers to become neighbors?
Definition
OSPF only

EIGRP doesn't require it and BGP will take the smaller of the two hold times.
Term
In EIGRP, what route is installed in the route table, the successor or the feasible successor?
Definition
The successor.
Term
What happens if an interface is not matched by an EIGRP network command?
Definition
EIGRP is not enabled on that interface at all.
Term
Does EIGRP stub routing prevent core routes from being advertised in the stub network?
Definition
No, stub networks limit Queries and limit SENT connected and summary routes (not received from core).
Term
What has an administrative distance of 20?
Definition
External BGP
Term
Which has a higher administrative distance, EIGRP or OSPF?
Definition
Depends.
EIGRP AD = 90
OSPF AD = 100
External EIGRP = 170
Term
What does a classful routing protocol use to determine the subnet of a route?
Definition
Its own mask (if it has an interface in the major network)
OR
the classful major network (if it doesn't)
Term
What is the default metric for routes redistributed into EIGRP?
Definition
0 (not valid)
EIGRP needs a metric.
Term
What routing protocols assigns a default metric of 20 to redistributed routes if none is configured?
Definition
OSPF
Term
What is the metric of a summary route?
Definition
The lowest-metric component subnet.
Term
Where is OSPF summarization configured?
Definition
OSPF summarizes in the under "router ospf"

EIGRP summarizes on the interface.
Term
When are summarized external routes not marked as external?
Definition
EIGRP does not mark summarized external routes as external.

OSPF does.
Term
What is the difference between "set ip next-hop" and "set ip default next-hop" in a policy-routing route-map?
Definition
set ip default next-hop only takes effect if there is no match in the routing table.
Term
What is the difference between "ip policy route-map SALLY" and "ip local policy route-map SALLY" ?
Definition
"ip policy route-map SALLY" is configured on an interface and applies to traffic coming into that router.

"ip local policy route-map SALLY" is global config that influences traffic sourced from router.
Term
What is the default metric type of redistributed routes in OSPF?
Definition
External Type 2 (E2)
Term
What is the default hold time for EIGRP?
Definition
15 seconds

= 3 * 5 sec hello
Term
What does an EIGRP Update with the INIT and RS bits indicate?
Definition
INIT and RS indicate the router is restarting.
Hellos will be sent with RS bit as long as router is restarting.
Term
What is ADV Router in the following? What is the Link ID?

Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 172.16.12.2 172.16.102.1 137 0x80000010 0x009B0E
Definition
ADV Router is the DR RID.

Link ID is the DR interface address.
Term
Is fast switching enabled by default with PBR?
Definition
No, you must configure "ip route-cache policy" to enable it.
Term
Is "set ip default" supported with fast-switched PBR?
Definition
No.
Term
Are there any match commands that are not supported when using fast-switched PBR?
Definition
Term
What is the function of the no-redistribution command on an NSSA router that is both ASBR and ABR?
Definition
The no-redistribution keyword would be necessary when you do not want the redistributed routes to enter your NSSA area, but you do want these routes to enter other normal areas.
Term
What can be set with PBR?
Definition
IP Precedence
IP Next Hop
Output Interface
Default Next Hop
Default Interface
Term
How is OSPF RID determined?
Definition
OSPF RID is:
1) set by "router-id" CLI
2) highest IP address of loopback
3) highest IP address of physical interface
Term
Can the advertised distance of the feasible successor be the same as the feasible distance of the successor route?
Definition
No, the advertised distance of the feasible successor must be LESS than the feasible distance of the successor.
Term
Why is the FD "Inaccessible" below?
#show ip eigrp topology zero
P 10.200.1.0/24, o successors, FD is Inaccessible
via 10.1.1.12 ( / ), S1/0
Definition
Zero successor routes (FD Inaccessible) aren't installed in the routing table because there is a route with a better AD.
Supporting users have an ad free experience!