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Zorluk: ZorTroubleshooting Routing, Default Gateways, and ACLs

An administrator is troubleshooting remote network connectivity for a client workstation configured with the following static IPv4 parameters:

- IP Address: 10.88.32.18010.88.32.180
- Subnet Mask: 255.255.240.0255.255.240.0
- Default Gateway: 10.88.48.110.88.48.1

The workstation can successfully reach local hosts within the 10.88.32.0/2010.88.32.0/20 range, but all attempts to communicate with external networks fail. Physical layer diagnostics and switchport configurations are verified to be fully operational. Which of the following represents the root cause of the connectivity failure?

  1. The configured default gateway IP address resides outside the host's IPv4 subnet boundary.Cevap
  2. B
    The host IP address is an unassignable subnet broadcast address for the /20 prefix.
  3. C
    The switch ports are assigned to separate untagged VLANs, preventing Layer 2 broadcast discovery.
  4. D
    The router gateway interface has dropped outbound frames due to a transport port and protocol mismatch.

Cevap

The configured default gateway IP address resides outside the host's IPv4 subnet boundary.
The correct option correctly identifies that the gateway IP address (10.88.48.110.88.48.1) is located on a different logical IPv4 subnet than the host (10.88.32.180/2010.88.32.180/20). A subnet mask of 255.255.240.0255.255.240.0 creates subnets in increments of 1616 in the third octet. The host's local subnet spans from 10.88.32.010.88.32.0 to 10.88.47.25510.88.47.255. Because 10.88.48.110.88.48.1 is outside this range, the host cannot communicate with its gateway to route traffic off the local network.

Adım Adım Çözüm

1
Determine the subnet increment and network boundaries for a /20 mask.
A mask of 255.255.240.0 has a 3rd octet block size of 256 - 240 = 16.
Calculating the subnet range identifies which IP addresses belong to the same local broadcast domain.
2
Identify the specific subnet range for host IP 10.88.32.180.
The network ID is 10.88.32.0 and the valid host range spans 10.88.32.1 through 10.88.47.254, with 10.88.47.255 as the broadcast address.
Evaluating the lower and upper bounds confirms the extent of local IP reachability.
3
Compare the configured default gateway address against the local subnet bounds.
The default gateway 10.88.48.1 falls into the next subnet block (10.88.48.0/20).
A host cannot ARP for or send traffic directly to a default gateway that does not reside within its local subnet.

Anahtar Kavram

Default Gateway Subnet Boundary Troubleshooting
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Konular

Troubleshooting Routing, Default Gateways, and ACLs

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