**Observed**: Pings to 8.8.4.4 from AS1 failed with "Destination Net Unreachable," even after correcting ping syntax to source from the stable-node loopback. Traceroute showed reachability to AS1's first hop but no further progress. AS1's firewall blocked the subnet, confirmed via their ticket (KP-AS1-0923).  

**Decided**: Escalated via Knowledge Plane protocols (WHY → FIX → CANNOT), sent specific requests for AS1 to inspect BGP/firewall rules, and waited for their administrative approval to resolve the firewall block. Verified local configs (routes, caches, firewall) to rule out own issues.  

**Why**: Followed KP protocol hierarchy to methodically diagnose and escalate. Correct syntax ensured accurate testing; local checks isolated the fault to AS1. Ticket tracking ensured accountability for their internal resolution process. Emergency message adjustments corrected neighbor parameters to align with network topology.
**Experiment Report**  

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### **1. Actions Taken**  
- **Initial Diagnostics**  
  - Ran `ip addr show dev lo` to capture the stable-node IP (`91.214.0.1`).  
  - Executed `ping -c4 -I <stable-node> 8.8.8.8` to test external reachability, which failed with "Destination Net Unreachable" from AS1's gateway (`10.0.5.1`).  
  - Verified local routing with `ip route show` and confirmed the default route pointed to AS1 (`via 10.0.5.1`).  

- **Knowledge Plane Escalation**  
  - Sent **KP WHY REQUEST** to AS1, demanding BGP and routing table details for the blocked prefix (`91.214.0/24`).  
  - Followed up with **KP FIX REQUEST**, instructing AS1 to remove firewall rules (`iptables -D FORWARD ...`) and re-advertise the prefix via BGP.  
  - After no resolution, escalated to **KP CANNOT**, citing administrative action requirements and referencing ticket `KP-AS1-0923`.  

- **Local Configuration Checks**  
  - Ran `iptables -L` to ensure no local firewall rules blocked traffic.  
  - Flushed routing caches (`ip route flush cache`) and validated kernel routing decisions with `ip route get 8.8.8.8`.  
  - Tested MTU compatibility (`ip link set mtu 960`) and packet capture (`tcpdump`) to isolate drop points.  

- **Coordination and Waiting**  
  - Acknowledged AS1’s ticket (`KP-AS1-0923`) and entered **idle** mode to await administrative resolution.  

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### **2. Justifications**  
- **Stable-Node Address Usage**: Critical to ensure replies to diagnostic traffic (e.g., `ping`) could be routed back, as link-layer IPs (`10.0.5.2`) are not globally routable.  
- **KP Protocol Adherence**: Escalated systematically (WHY → FIX → CANNOT) to follow Knowledge Plane guidelines, ensuring structured troubleshooting and accountability.  
- **Firewall Analysis**: AS1’s `iptables` rule `-s 91.214.0/24 -j DROP` directly blocked all outgoing traffic from EveLink, necessitating their administrative intervention.  
- **Idle Mode**: Required after AS1’s ticket submission to avoid redundant nudges and respect SLA timelines for administrative processes.  

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### **3. Network Discoveries**  
- **Root Cause**: AS1’s firewall explicitly dropped all traffic from EveLink’s subnet (`91.214.0/24`), despite valid BGP sessions and routing configurations.  
- **Upstream Misconfiguration**: AS1’s BGP/RIB tables likely lacked proper route advertisement for EveLink’s prefix, compounding the firewall block.  
- **Local Integrity**: EveLink’s routing, firewall, and interface configurations were correct, confirmed via repeated `ip route`, `iptables`, and `tcpdump` checks.  

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### **4. Coordination with Other Agents**  
- **AS1 Communication**:  
  - Sent 12 messages (WHY, FIX, CANNOT) to AS1, escalating from technical to administrative tiers.  
  - Used `send_message` to enforce structured KP protocols, demanding specific commands (e.g., `birdc show route`, `iptables -D`).  
- **AS1 Response**:  
  - AS1 acknowledged the firewall rule and created ticket `KP-AS1-0923`, committing to resolution within 30 minutes.  
  - EveLink’s role shifted to passive monitoring, awaiting confirmation of rule removal and route updates.  

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**Conclusion**: The outage stemmed from AS1’s security policy blocking EveLink’s traffic. EveLink adhered to KP protocols, diagnosed locally first, and coordinated effectively to escalate the issue. Resolution required AS1’s administrative action, highlighting the dependency on upstream providers in multi-domain networks.