Term
What is the default OSPF network type for a Frame-Relay point-to-point interface?
What is the Default Hello interval? |
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Definition
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Term
What is the default OSPF network type for a Frame-Relay point-to-multipoint interface?
What is the Default Hello interval? |
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Definition
|
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Term
| Which OSPF network types require neighbor configuration? |
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Definition
Nonbroadcast
Point-to-multipoint nonbroadcast |
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Term
| Which OSPF network types have a hello interval of 10 seconds? |
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Definition
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|
Term
| What OSPF network types elect DR/BDR? |
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Definition
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|
Term
| What is the Administrative Distance for a connected interface? |
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Definition
|
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Term
| What is the Administrative Distance for a IPv4 static route that points to an interface? |
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Definition
|
|
Term
| What is the Administrative Distance for EIGRP summary routes? |
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Definition
|
|
Term
| What is the Administrative Distance for an external BGP route? |
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Definition
|
|
Term
| What is the Administrative Distance for an internal EIGRP route? |
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Definition
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|
Term
| What is the Administrative Distance for an OSPF route? |
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Definition
|
|
Term
| What is the Administrative Distance for a RIP route? |
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Definition
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|
Term
| What is the Administrative Distance for an external EIGRP route? |
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Definition
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Term
| What is the Administrative Distance for an internal BGP route? |
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Definition
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Term
| What is the default percentage of bandwidth that EIGRP can use for updates? |
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Definition
|
|
Term
| What EIGRP messages are acknowledged? |
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Definition
|
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Term
| What are private ASNs used for confederation BGP? |
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Definition
|
|
Term
What is the default OSPF network type for a Frame-Relay physical interface?
What is the Default Hello interval? |
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Definition
|
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Term
| What is the default Hello timer and Dead interval for OSPF on broadcast networks? |
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Definition
Hello: 10 seconds
Dead: 40 seconds |
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Term
| In what state is the DR elected? |
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Definition
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Term
| If AS_PATH = {20 30}, what do we know about this NLRI? |
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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" |
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Term
| If the AS_PATH looks like this: (65534 54435), what do we know about this prefix? |
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Definition
| The "()" brackets indicate confederation AS numbers. |
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Term
| What type of LSA is sent when "default-information originate" is configured under the OSPF process? |
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Definition
| Type 5. "default-information-originate" makes the router an ASBR |
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Term
Name three conditions that must be met for a summary route to be advertised. |
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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. |
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Term
| What command is used to summarize redistributed routes in OSPF. |
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Definition
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Term
| What command is used to summarize internal OSPF routes at an ABR? |
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Definition
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Term
| By default, what eigrp routes are advertised TO a stub router? |
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Definition
| By default, all routes are advertised TO a stub. |
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Term
| By default, what routes will a stub EIGRP router advertise? |
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Definition
Summary and connected.
"EIGRP stubs are Sum-what Connected" |
|
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Term
| What types of authentication does EIGRP support? |
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Definition
|
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Term
| What is the default metric for EIGRP? |
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Definition
256 (delay + 10^7/BW)
Where bandwidth is the lowest bandwidth in the path, and delay is cumulative. |
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Term
| What are the metric weights from k1 to k5? |
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Definition
k1 = bandwidth = 1
k2 = load = 0
k3 = delay = 1
k4 = reliability = 0
k5 = mtu = 0
"Blind Ladies Don't Route Much" |
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Term
| What must be true for EIGRP to advertise a default route using the "ip default-network x.x.x.x" command? |
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Definition
1) The network must be classful
2) The classful network must be in routing table
3) EIGRP must be advertising the classful network. |
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Term
| Name three ways of limiting query scope in EIGRP. |
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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 |
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Term
| What must work for EIGRP neighbors to form? |
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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
|
|
Term
|
Definition
|
|
Term
| What is the EIGRP multicast address? |
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Definition
|
|
Term
| How often are EIGRP Hellos sent? |
|
Definition
| Every 5 seconds on fast links, 60 on slow links. |
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|
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 |
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|
Term
|
Definition
|
|
Term
| What happens if EIGRP neighbors don't have matching hello and hold times? |
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Definition
| They become neighbors anyway. EIGRP neighbors don't have to have matching hello and hold timers. |
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|
Term
Where is the following configured:
ip authentication mode eigrp 1 md5
ip authentication key-chain eigrp 1 MYCHAIN |
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Definition
| EIGRP enables authentication on the interface. |
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Term
| Why would you use "traffic-share min across-interfaces" in EIGRP? |
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Definition
| To only send traffic on minimum cost route but install all unequal-cost routes in the routing table for faster convergence. |
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Term
| What do you need to do to prevent core routes from being advertised to stub router? |
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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. |
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|
Term
| If a new router appears with a higher priority in an OSPF broadcast network, what will happen? |
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Definition
| Nothing. Current active DR and BDR are not pre-empted |
|
|
Term
| What is the purpose of the DR in OSPF? |
|
Definition
|
|
Term
| What is the OSFP cost formula? |
|
Definition
| Cost = reference bandwidth / bandwidth |
|
|
Term
| What is the default OSPF reference bandwidth? |
|
Definition
|
|
Term
| What is the OSPF cost of a FE link if the reference bandwidth is default? |
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Definition
| cost = ref / BW = 100 Mbps/ 100 Mbps= 1 |
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|
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) |
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Term
| When a DR is used, what state do non-DR/BDR neighbors stop at in the OSPF state machine? |
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Definition
| The Two-way state. The routers will continue with the rest of the state machine with DR and BDR routers. |
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|
Term
| What happens in the OSPF exstart state? |
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Definition
| router and DR determine who will be the master and establish sequence number for DDP exchange. |
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|
Term
| What OSPF packet contains LSA headers? |
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Definition
| Database Description Packet |
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|
Term
| When are DDP packets exchange in the OSPF state machine? |
|
Definition
| Routers exchange DDPs in the exchange state. |
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Term
| What happens during the Loading state in OSPF? |
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Definition
| Router sends LSR for any LSAs that it does not have (LSA headers were sent earlier in DDPs). Other router responds with LSU. |
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|
Term
| What does the Full State represent in OSPF? |
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Definition
| Router has LSDB as every other router and can run Dijkstra. |
|
|
Term
| What three packets are used for building OSPF adjacencies? |
|
Definition
|
|
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? |
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Definition
| Group pacing configured with "timers lsa-group-pacing" Default is 4 minutes. |
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Term
| What does "ip ospf flood-reduction" do? |
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Definition
| Sends LSA with the DoNotAge bit set (so router will not need to reflood LSA every MaxAge (30 minutes). |
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Term
| If multiple routes exist and the inter-area route costs less than the intra-area route, which one will OSPF use? |
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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 |
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Term
| What's in a Type 1 LSA, who sends it and in what area? |
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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. |
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Term
| What LSA type is produce by a DR and contains a list of all attached router? Where is this LSA flooded? |
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Definition
| Type 2 Network LSA is produce by DR and flooded in originating area. |
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Term
| What are Type 3 LSAs and who sends them? |
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Definition
| ABRs produce Type 3 Network Summary LSAs, summarizing Type 1 and 2 LSAs for forwarding into another area. |
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|
Term
| What does an ABR do with Network Summary LSAs from another ABR in a non-backbone area when calculating least-cost path? |
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Definition
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|
Term
| Who creates an ASBR Summary LSA and what type is it? |
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Definition
| ABRs create Type 4 ABSR Summary LSAs when flooding Type 5 LSAs to another area (lists ABR cost to ASBR). |
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Term
| What two LSAs are originated by ASBRs and where are they flooded? |
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Definition
Type 5 AS External LSA -- flooded through entire AS
Type 7 NSSA External LSA -- flooding through NSSA only |
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Term
| Where are Type 5 LSAs flooded and what do they describe? |
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Definition
| Type 5 AS External LSAs are flooded by ASBRs through the entire AS to advertise external routes. |
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Term
| What does a forwarding address of 0.0.0.0 mean in a Type 5 or Type 7 LSA? |
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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). |
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Term
| What area has Type 1,2 and 3 LSAs? |
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Definition
| Stub area has 1,2,3 only. Types 4 and 5 are blocked. |
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|
Term
| What area allows Type 1, Type 2 and summary-only Type 3 LSAs? |
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Definition
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|
Term
What does an ABR do when receiving a Type 7 NSSA LSA? |
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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. |
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Term
| What does the "not-advertise" option in the "summary-address" OSPF CLI do? |
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Definition
| Allows the NSSA router to set the P-bit to 0 (so ABR will not flood this LSA to other areas). |
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Term
| What is the order of preference if multiple types of OSPF routes exist to a destination? |
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Definition
| 1) Intra-area (regardless of cost!) 2) Inter-area 3) Type 1 External 4) Type 2 External |
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|
Term
| What is the Type 1 external cost to an ASBR in the same area? |
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Definition
| Cost = cost to ASBR + external cost |
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|
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 |
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|
Term
| What is the Type 2 External cost to a destination outside the the AS? |
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Definition
| External cost only (does not include cost to ASBR or ABR) |
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|
Term
| What configuration command would make OSPF area 1 totally stubby? |
|
Definition
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|
Term
| What CLI would make area 1 not so stubby? |
|
Definition
|
|
Term
What types of LSAs are allowed in area 192 below?
area 192 nssa no-summary |
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Definition
| Type 1,2 and summary only Type 3. Type 7 LSAs from ASBRs within area would be flooded also. |
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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 |
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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) |
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|
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)? |
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Definition
| area 192 nssa no-redistribution default-information-originate |
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|
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)? |
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Definition
| area 192 nssa no-redistribution default-information-originate |
|
|
Term
| Where is authentication configured in ospf? |
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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 |
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|
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. |
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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. |
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|
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" |
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|
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. |
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|
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 |
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|
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
|
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
|
|
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
|
|
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
|
|
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
|
|
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
|
|
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. |
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