300-410 Practice Test 14 — 15 Questions

Question 1

A large enterprise network is experiencing intermittent BGP session resets between R1 and R2. R1 has the following relevant configuration: 
! R1
control-plane
 service-policy input CoPP
!
access-list 100 permit tcp any any eq bgp
class-map match-all BGP-CLASS
 match access-group 100
!
policy-map CoPP
 class BGP-CLASS
  police 8000 conform-action transmit exceed-action drop
 class class-default
  police 1000000 conform-action transmit exceed-action drop
!
R2 shows: 
R2#show ip bgp summary
BGP router identifier 2.2.2.2, local AS number 65002
BGP table version is 1, main routing table version 1
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.1.1         4        65001   12345   12345        0    0    0 00:02:34        0
What is the root cause?

Accepted Answer

The BGP session is flapping because the CoPP policy drops BGP keepalive packets when the police rate is exceeded.. The CoPP policy is policing BGP traffic to 8000 bps. If the BGP session carries a full routing table, the update messages can exceed this rate, causing drops. The router drops packets, leading to BGP hold timer expiry and session resets. The fix is to increase the police rate for BGP traffic or use a more specific match to avoid policing keepalives.

Answer

The access-list 100 is misconfigured; it should match TCP port 179 specifically.

Answer

The class-default police rate is too low, causing all traffic to be dropped, including BGP.

Answer

The CoPP policy should be applied to the control-plane input direction, but the service-policy is missing the 'control-plane' keyword.

Question 2

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show policy-map control-plane input class class-default

Class-map: class-default (match-any)
  0 packets, 0 bytes
  5 minute offered rate 0 bps, drop rate 0 bps
  Match: any
  police:
      cir 1000000 bps, bc 31250 bytes, be 31250 bytes
    conformed 0 packets, 0 bytes; actions:
      transmit
    violated 0 packets, 0 bytes; actions:
      drop
    conformed 0 bps, exceed 0 bps, violated 0 bps

What does this output indicate?

Accepted Answer

The CoPP policy is not matching any traffic, indicating a possible ACL or class-map misconfiguration.. The command shows the CoPP policy applied to the control plane input for the default class. The output indicates that no traffic has matched this class, meaning all control plane traffic is being policed at a rate of 1 Mbps, with conforming traffic transmitted and violating traffic dropped.

Answer

The CoPP policy is dropping all traffic due to a misconfigured CIR.

Answer

The CoPP policy is working correctly and policing traffic at 1 Mbps.

Answer

The CoPP policy is only applied to the output direction.

Question 3

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show ip access-lists CoPP-ACL

Extended IP access list CoPP-ACL
    10 permit tcp host 10.1.1.1 any eq bgp (100 matches)
    20 permit udp any any eq 67 (50 matches)
    30 permit icmp any any echo (200 matches)
    40 deny ip any any (500 matches)

What does this output indicate?

Accepted Answer

The ACL is permitting DHCP and ICMP echo traffic, but dropping all other traffic.. The ACL shows traffic matching various protocols. The 'deny ip any any' at line 40 indicates that all unmatched traffic is being denied, which could be part of a CoPP policy to drop unwanted traffic to the control plane.

Answer

The ACL is blocking all BGP traffic from 10.1.1.1.

Answer

The ACL is applied to the control plane interface and is dropping all traffic.

Answer

The ACL has a misconfiguration because the deny statement should be at the top.

Question 4

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show policy-map control-plane input class CoPP-Class

Class-map: CoPP-Class (match-all)
  1500 packets, 120000 bytes
  5 minute offered rate 10000 bps, drop rate 5000 bps
  Match: access-group name CoPP-ACL
  police:
      cir 8000 bps, bc 1500 bytes, be 1500 bytes
    conformed 1000 packets, 80000 bytes; actions:
      transmit
    exceeded 500 packets, 40000 bytes; actions:
      drop
    conformed 8000 bps, exceed 2000 bps, violated 0 bps

What does this output indicate?

Accepted Answer

The CoPP policy is causing packet loss for traffic that exceeds the 8 kbps rate, which may impact legitimate control plane traffic.. The output shows that the CoPP policy is policing traffic matching the CoPP-ACL. The offered rate is 10 kbps, but the CIR is 8 kbps, resulting in 500 packets exceeding the rate and being dropped. This indicates that control plane traffic is being throttled.

Answer

The CoPP policy is dropping all traffic because the CIR is too low.

Answer

The CoPP policy is not applied correctly because the drop rate is higher than the conform rate.

Answer

The CoPP policy is working as intended with no issues.

Question 5

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# debug ip ospf adj

OSPF adjacency debugging is on
R1#
*Mar  1 00:05:23.123: OSPF: Rcv pkt from 10.1.1.2, FastEthernet0/0, area 0.0.0.0, packet type: 1 (Hello)
*Mar  1 00:05:23.123: OSPF: 2 Way Communication to 10.1.1.2 on FastEthernet0/0, state 2WAY
*Mar  1 00:05:23.124: OSPF: Send immediate hello to nbr 10.1.1.2, src address 10.1.1.1, on FastEthernet0/0
*Mar  1 00:05:23.124: OSPF: Rcv pkt from 10.1.1.2, FastEthernet0/0, area 0.0.0.0, packet type: 2 (DBD)
*Mar  1 00:05:23.125: OSPF: Rcv DBD from 10.1.1.2, seq 0x1234, opts 0x2, flag 0x7, mtu 1500 state EXSTART
*Mar  1 00:05:23.126: OSPF: Nbr 10.1.1.2 has state FULL

What does this output indicate?

Accepted Answer

OSPF adjacency is established successfully, indicating CoPP is not blocking OSPF traffic.. The debug output shows OSPF adjacency formation with neighbor 10.1.1.2. The sequence of packets (Hello, DBD) and the transition to FULL state indicate that the adjacency is established successfully. This can be used to verify that CoPP is not dropping OSPF packets.

Answer

OSPF adjacency is failing due to CoPP dropping Hello packets.

Answer

OSPF is experiencing packet loss due to MTU mismatch.

Answer

OSPF is stuck in EXSTART state due to CoPP.

Question 6

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show ip route summary

IP routing table name: Default-IP-Routing-Table (0x0)
IP routing table maximum-paths: 32
Route entry limits: 1000000 active, 2000000 total
Number of prefixes: 500
Prefixes with memory: 500
Number of paths: 600
Paths with memory: 600
Number of operations: 1200
Number of deleted entries: 0

What does this output indicate?

Accepted Answer

The routing table has 500 prefixes, indicating that routing protocols are functioning and CoPP is not blocking updates.. The command shows the IP routing table summary. It indicates that there are 500 prefixes and 600 paths in the routing table, with no deleted entries. This can be used to verify that CoPP is not affecting routing updates by checking if the routing table is stable.

Answer

The routing table is empty due to CoPP dropping routing updates.

Answer

The routing table has too many prefixes, causing CoPP to drop packets.

Answer

The routing table is not being updated due to a CoPP policy.

Question 7

What is the default CoPP behavior for traffic that does not match any class in the policy-map?

Accepted Answer

Transmitted. If a policy-map has no explicit 'class class-default' statement, unmatched traffic is implicitly permitted and transmitted without policing.

Answer

Dropped

Answer

Logged and dropped

Answer

Routed to the management plane

Question 8

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show bgp ipv4 unicast 10.1.1.0/24

BGP routing table entry for 10.1.1.0/24, version 10
Paths: (1 available, best #1, table default)
  Advertised to update-groups:
     1
  Refresh Epoch 1
  Local
    10.1.1.2 from 10.1.1.2 (10.1.1.2)
      Origin IGP, metric 0, localpref 100, valid, external, best
      Last update: Mon Mar  1 00:05:23 2024

What does this output indicate?

Accepted Answer

BGP is functioning correctly, and CoPP is not interfering with BGP sessions.. The BGP route for 10.1.1.0/24 is present and valid, with a last update time of 00:05:23. This indicates that BGP updates are being received and processed, suggesting CoPP is not blocking BGP traffic.

Answer

BGP is not receiving updates due to CoPP dropping packets.

Answer

BGP is stuck in idle state due to CoPP.

Answer

BGP is only advertising routes locally.

Question 9

Which statement about CoPP and IPv6 control plane traffic is correct?

Accepted Answer

CoPP can police IPv6 traffic using the same policy-map as IPv4. CoPP can classify and police IPv6 control plane traffic using the same policy-map framework, but IPv6-specific protocols like OSPFv3 or RIPng must be matched using appropriate ACLs or class-maps.

Answer

CoPP does not support IPv6 traffic

Answer

IPv6 traffic is automatically classified as critical

Answer

IPv6 control plane traffic is not subject to CoPP

Question 10

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show bgp neighbors 10.1.1.2 advertised-routes

BGP table version is 10, local router ID is 10.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete

Network          Next Hop            Metric LocPrf Weight Path
*> 10.2.2.0/24      0.0.0.0                  0         32768 i

Total number of prefixes 1

What does this output indicate?

Accepted Answer

BGP is advertising routes correctly, and CoPP is not affecting outbound updates.. The command shows routes advertised to BGP neighbor 10.1.1.2. Only one prefix (10.2.2.0/24) is being advertised. This can be used to verify that CoPP is not preventing route advertisement, though the output does not show any errors.

Answer

BGP is not advertising routes due to CoPP dropping update packets.

Answer

BGP is receiving routes but not advertising them due to CoPP.

Answer

BGP session is down due to CoPP.

Question 11

What is the default CoPP policer action for packets that exceed the committed information rate (CIR)?

Accepted Answer

Drop. By default, the CoPP policer uses a single-rate two-color marker where packets exceeding the CIR are dropped.

Answer

Transmit with best-effort

Answer

Set DSCP to 0

Answer

Queue for later transmission

Question 12

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show bgp neighbors 10.1.1.2 received-routes

BGP table version is 10, local router ID is 10.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete

Network          Next Hop            Metric LocPrf Weight Path
*> 10.3.3.0/24      10.1.1.2                 0    100      0 i

Total number of prefixes 1

What does this output indicate?

Accepted Answer

BGP is receiving routes correctly, and CoPP is not interfering with inbound updates.. The command shows routes received from BGP neighbor 10.1.1.2. One prefix (10.3.3.0/24) is being received. This indicates that BGP updates are being received, so CoPP is not blocking inbound BGP traffic.

Answer

BGP is not receiving any routes due to CoPP dropping updates.

Answer

BGP is receiving routes but not installing them in the routing table due to CoPP.

Answer

BGP session is flapping due to CoPP.

Question 13

A network engineer runs the following command to troubleshoot a Control Plane Policing (CoPP) issue:

R1# show ip ospf interface detail

FastEthernet0/0 is up, line protocol is up
  Internet Address 10.1.1.1/24, Area 0.0.0.0, Attached via Network Statement
  Process ID 1, Router ID 10.1.1.1, Network Type BROADCAST, Cost: 1
  Topology-MTID Cost    Disabled    Shutdown      Topology Name
        0        1        no          no            Base
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 10.1.1.1, Interface address 10.1.1.1
  Backup Designated router (ID) 10.1.1.2, Interface address 10.1.1.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:03
  Supports Link-local Signaling (LLS)
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 25
  Last flood scan time is 0 msec, maximum is 4 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 10.1.1.2  (Backup Designated Router)
  Suppress hello for 0 neighbor(s)

What does this output indicate?

Accepted Answer

OSPF is operating normally with one neighbor, suggesting CoPP is not impacting OSPF.. The detailed OSPF interface output shows that FastEthernet0/0 is operational, with a neighbor count of 1 and an adjacent neighbor (10.1.1.2) as BDR. This indicates OSPF is functioning correctly, and CoPP is not blocking OSPF packets.

Answer

OSPF is not forming adjacencies due to CoPP dropping Hello packets.

Answer

OSPF is experiencing DR/BDR election issues due to CoPP.

Answer

OSPF is not receiving Hello packets due to CoPP.

Question 14

Which CoPP feature allows the control plane to process packets from a specific source IP address without rate limiting?

Accepted Answer

Control Plane Protection (CPPr) exception. Control Plane Protection (CPPr) allows the creation of exceptions for specific source IP addresses or subnets using the 'exception' keyword within a class-map.

Answer

CoPP aggregate policer

Answer

QoS pre-classify

Answer

Policy-map 'set' action

Question 15

Drag and drop the steps to troubleshoot Control Plane Policing (CoPP) adjacency or connectivity failures into the correct order, from first to last.

Accepted Answer

Check if CoPP is applied to the control-plane. Troubleshooting CoPP failures starts by checking if the control-plane policy is applied, then verifying the class-map matches the correct protocol, checking for dropped packets, temporarily disabling CoPP to test, and finally adjusting the policy to permit the necessary traffic. This systematic approach isolates the issue without disrupting the network.