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Zorluk: ZorTroubleshooting Routing, Default Gateways, and ACLs

A network administrator is troubleshooting an intermittent reachability issue affecting a Linux web server located in a corporate DMZ subnet (10.50.100.0/2410.50.100.0/24). Internal workstations on the LAN (192.168.10.0/24192.168.10.0/24) can ping their local default gateway (192.168.10.1192.168.10.1), but cannot reach the web server at 10.50.100.4510.50.100.45 on TCP port 443. The administrator executes diagnostic commands and observes the following output:

text C:\Users\admin> traceroute 10.50.100.45 traceroute to 10.50.100.45, 30 hops max, 60 byte packets 1 192.168.10.1 (192.168.10.1) 1.102 ms 0.985 ms 0.950 ms 2 10.200.1.1 (10.200.1.1) 3.421 ms 3.211 ms 3.105 ms 3 * * * 4 * * *

A inspect of the gateway router (10.200.1.110.200.1.1) inbound Access Control List (ACL) on the interface facing the core router reveals:

text 10 permit tcp 192.168.10.0 0.0.0.255 10.50.100.0 0.0.0.255 eq 80 20 permit icmp 192.168.10.0 0.0.0.255 10.50.100.0 0.0.0.255 30 deny ip any any

Additionally, direct diagnostic checks on the web server (10.50.100.4510.50.100.45) show its IPv4 address is configured as 10.50.100.45/2410.50.100.45/24 with a default gateway configured as 10.50.101.110.50.101.1.

Which TWO of the following underlying issues are preventing workstation connections to the web server over HTTPS?

  1. The Access Control List on the gateway router lacks a rule permitting TCP port 443 traffic, causing HTTPS packets to trigger the implicit or explicit deny rule.Cevap
  2. The web server's default gateway IP address resides on a different IP subnet than its assigned interface address, preventing it from routing return packets.Cevap
  3. C
    The traceroute utility failed because ICMP Echo Request traffic is strictly blocked by line 20 of the router's inbound Access Control List.
  4. D
    The web server is automatically assigning itself an APIPA address because the gateway router is unable to act as a DHCP relay agent.

Cevap

The two issues preventing HTTPS connectivity are: 1) The ACL lacks a rule permitting TCP port 443 traffic (causing packets to be denied), and 2) The web server's default gateway is configured on a completely different subnet (10.50.101.110.50.101.1 vs 10.50.100.0/2410.50.100.0/24).
Two independent issues prevent HTTPS connections. First, the ACL permits TCP port 80 and ICMP, but lacks a rule for TCP port 443, causing HTTPS packets to hit line 30 ('deny ip any any'). Second, the server's IP address is on subnet 10.50.100.0/2410.50.100.0/24, but its gateway is set to 10.50.101.110.50.101.1, which is on a different subnet. A default gateway must reside on the local subnet to be reachable.

Adım Adım Çözüm

1
Analyze the Access Control List entries on gateway router 10.200.1.1
The ACL permits TCP port 80 and ICMP, but has no entry for TCP port 443. Port 443 traffic matches line 30 ('deny ip any any') and gets dropped.
HTTPS connections require TCP port 443 to be permitted through intermediate firewall/ACL filters.
2
Evaluate host IP address configuration on the destination server
The server's IP address 10.50.100.45/2410.50.100.45/24 belongs to subnet 10.50.100.0/2410.50.100.0/24. Its configured default gateway 10.50.101.110.50.101.1 belongs to 10.50.101.0/2410.50.101.0/24.
A host must have a default gateway that resides within its own local IP subnet scope to communicate with out-of-subnet hosts.

Anahtar Kavram

Routing, Default Gateway Subnet Alignment, and ACL Traffic Filtering
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