Juniper Networks Certified Internet Associate Exam
15 questions. Answers and explanations can be found at the end of the quiz.
courtesy of Sybex
Questions
1. A unicast packet is flowing through the Packet Forwarding Engine. Which ASIC receives the packet after the incoming PIC I/O Manager ASIC performs its functions?
A. Incoming I/O Manager ASIC
B. Outgoing I/O Manager ASIC
C. Incoming Distributed Buffer Manager ASIC
D. Outgoing Distributed Buffer Manager ASIC
2. When you're committing your configuration, what command allows the router to automatically return to a previous configuration?
A. commit
B. commit and-quit
C. commit check
D. commit confirmed
3. What prefix length is assigned to an IPv4 address if you do not specify one in the configuration?
A. The command fails the syntax check and is not placed into the candidate configuration.
B. The command fails the commit check and the configuration is not made active.
C. The router assigns a /32 prefix length to the IP address.
D. The router assigns a prefix length which represents the classful network of the address.
4. Your router has learned about the 151.10.0.0 /16 route from protocols Static, RIP, OSPF, and IS-IS. Which version of the route will the router use?
A. Static
B. RIP
C. OSPF
D. IS-IS
5. When is the default routing policy applied?
A. During the evaluation of each applied policy
B. Only when explicitly referenced
C. At the beginning of every policy chain
D. At the end of every policy chain
6. Which of the following would correctly identify all routes more specific than 10.0.0.0 /16?
A. route-filter 10.0.0.0/16 longer
B. route-filter 10.0.0.0/16 orlonger
C. route-filter 10.0.0.0/16 upto /32
D. route-filter 10.0.0.0/17 orlonger
7. When would a RIP router send a Request message?
A. When the routing process terminates
B. When the routing process activates
C. At the end of the Update timer
D. At the end of the Hold-Down timer
8. Two OSPF routers forming an adjacency have just finished exchanging database description packets. What happens next?
A. They exchange hello packets to agree on authentication.
B. They exchange link-state updates when their connected networks change.
C. They send link-state requests to get additional database information from the neighbor.
D. They transition their adjacency to the ExStart state.
9. Four OSPF routers come online at the same time on a broadcast segment. Based on the properties shown, which router would be elected the designated router for the segment?
A. Priority = 50, router ID = 10.0.1.10
B. Priority = 50, router ID = 10.0.100.100
C. Priority = 25, router ID = 10.0.1.100
D. Priority = 100, router ID = 1.0.1.10
10. An IS-IS router with a NET ID of 49.1234.4321.1921.6801.6001.00 can form a Level 1 adjacency with which other system?
A. 49.4321.1921.6806.4001.00
B. 49.4321.1921.6801.6001.00
C. 49.1234.4321.1921.6806.4001.00
D. 49.1234.4321.1921.6801.6001.00
11. The following four IS-IS routers are adjacent on a broadcast link. Which router is elected the Designated Intermediate System for the segment?
A. Priority of 25 and MAC address of 00:90:69:90:50:11
B. Priority of 64 and MAC address of 00:90:69:96:87:46
C. Priority of 64 and MAC address of 00:90:69:56:70:79
D. Priority of 127 and MAC address of 00:90:69:31:55:91
12. How do the advertisement rules differ for IBGP and EBGP peers?
A. EBGP peers advertise only active routes, while IBGP peers advertise all routes.
B. EBGP peers advertise routes learned from both EBGP and IBGP peers, while IBGP peers do not advertise IBGP-learned routes.
C. IBGP and EBGP routers advertise all routes to all peers.
D. IBGP peers advertise routes learned from both IBGP and EBGP peers, while EBGP peers do not advertise EBGP-learned routes.
13. Which rendezvous point mechanism is an integrated part of the PIMv2 specification?
A. Local RP
B. Static RP
C. Auto-RP
D. Bootstrap router
14. Firewall filters can be used to accept, discard, or reject packets based on which of the following criteria? (Choose three)
A. IP address
B. MAC address
C. Protocol type
D. Well-known port name
15. In a network using MPLS, which direction is an RSVP Path message sent during the establishment of a label-switched path?
A. Upstream to the ingress router
B. Downstream to the ingress router
C. Upstream to the egress router
D. Downstream to the egress router
Answers
1. Answer: A. The flow of an IPv4 unicast packet through the Juniper Networks Packet Forwarding Engine follows the following sequence:
- A data packet arrives on one of the router's interfaces. The PIC I/O Manager ASIC formulates the packet and performs link-layer error checking, if appropriate.
- The PIC I/O Manager ASIC transmits the data packet, complete with Layer 2 and Layer 3 headers, to the I/O Manager ASIC on its Flexible PIC Controller (FPC).
- The I/O Manager ASIC verifies the integrity of the Layer 2 and Layer 3 headers. Provided a valid protocol packet remains, the I/O Manager ASIC removes the Layer 2 header and segments the data packet into 64-byte J-cells and sends those J-cells to the Distributed Buffer Manager ASIC.
- The Distributed Buffer Manager ASIC begins to receive J-cells from the I/O Manager ASIC. The notification cell is built and is transmitted to the Internet Processor ASIC
- The J-cells that make up the data packet are stored in the shared memory pool. Each FPC supplies the physical components of the shared memory, and the Distributed Buffer Manager ASIC sends the packet's J-cells to each FPC in the router on a round-robin basis.
- The I/O Manager ASIC on each FPC receives the J-cells and stores them in its physical memory as instructed by the Distributed Buffer Manager ASIC.
- While the J-cells are being stored in memory, the Internet Processor ASIC receives the notification cell and performs a route lookup in the forwarding table. The next-hop router along the path of the route and the outgoing interface on the router is determined. This next-hop information is stored in the notification cell, which now becomes the result cell.
- The Internet Processor ASIC sends the result cell to the Distributed Buffer Manager ASIC, which examines the cell to locate the outgoing interface. The result cell is then sent to the appropriate FPC for queuing and transmission.
- The I/O Manager ASIC queues the result cell and applies appropriate queuing mechanisms. When the result cell reaches the head of the queue, the I/O Manager ASIC requests the packet's J-cells from the Distributed Buffer Manager ASIC.
- The Distributed Buffer Manager ASIC copies the J-cells from the packet storage buffer and sends them to the I/O Manager ASIC on the outgoing FPC.
- The I/O Manager ASIC re-forms the data packet into a single unit and alters any protocol TTL values. The ASIC then appends the appropriate Layer 2 header information and sends the packet to the PIC I/O Manager ASIC.
- The PIC I/O Manager ASIC performs any link-layer duties, if required, and transmits the data packet out the router's interface.
Therefore, after the incoming PIC I/O Manager ASIC performs its functions, it sends the packet to the incoming I/O Manager ASIC on its local FPC.
2. Answer: D. The commit confirmed command allows the router to return to the previous configuration automatically after the expiration of the default 10-minute timer. The timer may be cancelled by the commit command, which allows the current active configuration to continue being used. The commit check command performs a syntax and semantic check of the candidate configuration, but does not apply it the router. The commit and-quit command applies the candidate configuration to the router and exits the user from configuration mode.
3. Answer: C. When an IP address is entered into the candidate configuration of a Juniper Networks router without the specification of a prefix length, the command is accepted by the router and the configuration may be activated and used. In this situation, the JUNOS software automatically assigns a 32-bit prefix length to the address. No other prefix length may be applied to the address as the JUNOS software doesn't use the concept of classful routing.
4. Answer: A. The JUNOS software always prefers the version of a route which has the lowest preference value assigned to it. These preference values are unique to the JUNOS software and are set to the following values by default:
- Direct-0
- Local-0
- Static-5
- RSVP-7
- LDP-9
- OSPF internal routes-10
- IS-IS Level 1 internal routes-15
- IS-IS Level 2 internal routes-18
- RIP-100
- Aggregate-130
- OSPF external routes-150
- IS-IS Level 1 external routes-160
- IS-IS Level 2 external routes-165
- BGP-170
Hence, the version of the 151.10.0.0 /16 route learned via the static route is preferred by the local router.
5. Answer: D. Each protocol within the JUNOS software has a default routing policy applied which mimics the operation of the protocol itself. When you apply a policy created on the router to a protocol, this default policy is automatically placed at the end of the policy chain.
6. Answer: A. Each route-filter defined in the JUNOS software contains a match-type which more specifically defines the number of routes which match the route-filter. The match-types include:
- exact -- Matches just the route specified in the route-filter.
- orlonger -- Matches the route specified in the route-filter and all routes more specific than the specified route.
- longer -- Matches only the routes which are more specific than the route specified in the route-filter.
- upto -- Matches the route specified in the route-filter as well as routes more specific than the specified route whose prefix length is between the specified route and the supplied second prefix.
- prefix-length-range -- Matches routes which share the same most significant bits with the route specified in the route-filter but whose prefix lengths fall between the two supplied prefixes.
- through -- Matches the two specified routes exactly as well as all routes which fall between the two on the internal radix tree.
In the question above, the longer keyword identifies all prefixes more specific than 10.0.0.0 /16. Should either the upto or orlonger keywords been used, the 10.0.0.0 /16 route would also be included in the match. The 10.0.0.0/17 orlonger option ignores the 10.0.128.0 /17 point on the radix tree and all points more specific than it.
7. Answer: B. When the routing process activates, a RIP router will send a Request message to all neighbors asking for their entire routing table. A Response message is transmitted at the end of the Update timer, while no messages are sent by either the routing process terminating or the Hold-Down timer expiring.
8. Answer: C. When two OSPF routers are forming an adjacency, they first establish bi-directional communications. They then elect one router to control the database transfer process and exchange database description packets which contain just link-state advertisement header information. When this process completes, each router may request information from the neighbor using a link-state request packet. This allows the local router to acquire additional database information for unknown or out-of-date link-state advertisements.
9. Answer: D. The election of a new designated router (DR) only occurs when no current DR is active on the segment. In our example, this is the case as all of the routers have just started. The first criterion evaluated in the election process is the highest priority value of any router. In the event of a priority tie, the second criterion evaluated is the highest router ID of the routers. Hence, even though the router in option D has the lowest router ID, it has the highest of all the routers shown.
10. Answer: C. The two requirements for forming an IS-IS Level 1 adjacency include the same defined area address and a unique system ID value. The sample router has an area address of 49.1234.4321 and a system ID of 1921.6801.6001. The routers in options C and D share this area address, but the router in option C has a unique system ID value. This is the neighbor with which the sample router can form a Level 1 adjacency.
11. Answer: D. The first criterion evaluated in the election process of a DIS is the highest priority value of any router on the segment. In the event of a priority tie, the second criterion evaluated is the highest MAC address of the routers. The router in option D has the highest priority of all the routers, so it is elected the DIS for the segment.
12. Answer: B. By default, a BGP router may only advertise active BGP routes to a peer based on the type of peering session and the source of the routing knowledge. Routes are transmitted across an EBGP peering session when the active BGP routes were learned from either another EBGP peer or any established IBGP peer. Routes are transmitted across an IBGP peering session only when the active BGP routes were learned from an EBGP peer. In other words, an IBGP peer will not re-advertise IBGP-learned routes.
13. Answer: D. The PIMv2 specification details the operation of the bootstrap router as a dynamic method for propagating knowledge of the rendezvous point (RP) in a multicast domain. The static RP option is specific to a single router and doesn't use PIM at all. Auto-RP is a proprietary Cisco Systems RP election mechanism which is supported by the JUNOS software. Finally, the local RP option is used for all three forms of RP elections and simply allows the local router to perform the functions of an RP.
14. Answers: A, C, D. A firewall filter in the JUNOS software operates on the Internet Processor ASIC, which only receives and evaluates IP header information. Of the listed choices, only options A, C, and D are contained in the IP header and are able to be evaluated by an applied firewall filter. The Internet Processor ASIC never views the MAC address of incoming packets, so it is not eligible for use in a filter.
15. Answer: D. When a label-switched path is being established by RSVP, the ingress router generates a Path message and sends it downstream towards the egress router.
Questions provided by Sybex from the title "JNCIA: Juniper Networks Certified Internet Associate Study Guide" (Sybex, 2003). To order this title or "JNCIP: Juniper Networks Certified Internet Professional Study Guide" (Sybex, 2003), visit Sybex.com. SPECIAL PROMOTION: Those who order online with the following promo code can take 40% off the list price of these titles and received free shipping within the continental U.S.: JUNIPER01. Offer expires July 25, 2003.
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