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Zorluk: ZorTroubleshooting Routing, Default Gateways, and ACLs

A network administrator is troubleshooting an issue where a client workstation cannot reach an internal database server located at 172.28.15.100172.28.15.100. The administrator collects the host settings and router interface details:

Host Settings:
- IP Address: 10.50.10.4510.50.10.45
- Subnet Mask: 255.255.255.192255.255.255.192 (/26/26)
- Default Gateway: 10.50.10.6510.50.10.65

Router Interface (GigabitEthernet0/0) & Inbound ACL:
- Interface IP: 10.50.10.1/2610.50.10.1/26
- Applied Inbound Access Control List:
- `line 10: permit tcp 10.50.10.0 0.0.0.63 host 172.28.15.100 eq 3306`
- `line 20: deny ip any any`

Which TWO of the following issues are directly preventing or obstructing successful communication and verification between the workstation and the database server?

  1. The host's configured default gateway (10.50.10.6510.50.10.65) falls outside the usable IP range (10.50.10.110.50.10.1–10.50.10.6210.50.10.62) of the configured /26/26 subnet.Cevap
  2. The inbound ACL on GigabitEthernet0/0 permits only TCP port 3306, causing standard diagnostic ICMP ping tests to be blocked by the explicit deny rule.Cevap
  3. C
    The /26/26 subnet mask allows a maximum of 30 usable host IP addresses, causing an IP address conflict with the router interface.
  4. D
    The host has assigned itself an APIPA address because the router interface failed to act as a DHCP relay agent.

Cevap

The host's default gateway is misconfigured outside its /26/26 subnet boundary, and the router ACL drops ICMP diagnostic traffic due to permitting only TCP port 3306.
The host cannot reach external networks because its gateway IP (10.50.10.6510.50.10.65) is outside its local /26/26 subnet (10.50.10.0/2610.50.10.0/26, usable IPs 10.50.10.110.50.10.1–10.50.10.6210.50.10.62). Additionally, network troubleshooting via ICMP ping fails because the inbound ACL only permits TCP port 3306 traffic, causing ICMP to hit the explicit deny rule on line 20.

Adım Adım Çözüm

1
Analyze the subnet boundaries for the host IP configuration.
A subnet mask of 255.255.255.192255.255.255.192 (/26/26) yields 256−192=64256 - 192 = 64 addresses per subnet. Subnet range: 10.50.10.010.50.10.0 to 10.50.10.6310.50.10.63. Usable range: 10.50.10.110.50.10.1 to 10.50.10.6210.50.10.62.
The configured default gateway 10.50.10.6510.50.10.65 resides on subnet 10.50.10.64/2610.50.10.64/26, making it unreachable to the host on 10.50.10.45/2610.50.10.45/26.
2
Evaluate the Access Control List (ACL) entries on interface GigabitEthernet0/0.
Line 10 permits only `tcp` traffic on port 3306. ICMP traffic hits line 20 (`deny ip any any`).
Network administrators commonly use `ping` (ICMP) for initial diagnostic tests. Since ICMP is not explicitly permitted before line 20, ICMP diagnostic traffic will fail even if Layer 3 routing is established.

Anahtar Kavram

Subnet Boundary & Default Gateway Verification, ACL Rule Filtering
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Konular

Troubleshooting Routing, Default Gateways, and ACLs

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