gabrielmoreira Linux Host Network Operations
Testbed Requirements
Linux hosts must be defined in the pyATS testbed with os: linux. See pyats-linux-system for the testbed YAML format.
How to Call
All commands use pyats_run_linux_command:
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"<command>"}'
Commands
Interface Configuration
All Interfaces
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"ifconfig"}'
Returns all interfaces with: IP address, netmask, broadcast, MAC address, MTU, RX/TX packets, RX/TX errors, RX/TX bytes, flags (UP/RUNNING/MULTICAST).
What to check:
- Interface UP/DOWN state — is the expected interface active?
- IP address correctness — does it match NetBox/Nautobot records?
- RX/TX errors — non-zero errors indicate physical or driver issues
- MTU — verify jumbo frames (9000) or standard (1500) as expected
- Dropped packets — may indicate buffer or rate-limit issues
Specific Interface
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"ifconfig eth0"}'
Common interfaces to inspect:
eth0/ens192— Primary management interfacedocker0— Docker bridge networklo— Loopback (verify 127.0.0.1)bond0— NIC bonding/teamingvlan100— VLAN sub-interfacetun0/wg0— VPN tunnel interfacesbr-*— Docker/bridge networks
Routing Tables
Full Routing Table (All Tables)
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"ip route show table all"}'
Returns routes from ALL routing tables — main, local, custom policy tables. This is the most comprehensive route view on a Linux host.
What to check:
- Default gateway present and correct
- Expected subnets reachable via correct interfaces
- Policy routing tables (table 100, table 200, etc.) configured correctly
- No blackhole or unreachable routes (unless intentional)
- Metric values — lower metric = preferred path
Legacy Route Command
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"route"}'
Legacy route command — shows the kernel IP routing table (main table only). Prefer ip route show table all for complete view.
Route with Flags
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"route -n"}'
The -n flag shows numeric addresses (no DNS resolution). Other useful flags:
route -n— Numeric output (faster, no DNS dependency)route -e— Extended information (likenetstat -r)
Network Connections
Routing Table via netstat
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"netstat -rn"}'
netstat -rn shows the kernel routing table in numeric format. Equivalent to route -n but with netstat-style output columns: Destination, Gateway, Genmask, Flags, MSS, Window, irtt, Iface.
Route flags:
U— Route is upG— Route uses a gatewayH— Target is a host (not a network)D— Created by ICMP redirectM— Modified by ICMP redirect
Workflows
1. Linux Network Health Check
pyats_list_devices → identify Linux hosts in testbed
→ pyats_run_linux_command(host, "ifconfig") → check interface states
→ pyats_run_linux_command(host, "ip route show table all") → verify routing
→ pyats_run_linux_command(host, "netstat -rn") → cross-reference routes
→ Flag: interfaces down, missing routes, error counters > 0
→ Severity-sort → GAIT
2. Linux Network Audit
pyats_list_devices → identify all Linux hosts
→ pyats_run_linux_command per host ("ifconfig") → collect interface data
→ Cross-reference IPs with NetBox/Nautobot IPAM → flag drift
→ pyats_run_linux_command per host ("ip route show table all") → collect routes
→ Verify default gateways match expected values
→ GAIT
3. Multi-Host Routing Comparison
pyats_run_linux_command(host-1, "ip route show table all") → host 1 routes
→ pyats_run_linux_command(host-2, "ip route show table all") → host 2 routes
→ Compare: same subnets, same gateways, same metrics?
→ Flag asymmetric routing or missing routes
→ GAIT
4. Interface Error Investigation
pyats_run_linux_command(host, "ifconfig") → check all interfaces
→ Identify interfaces with non-zero RX/TX errors or drops
→ pyats_run_linux_command(host, "ifconfig eth0") → deep dive on problem interface
→ Correlate with network device interfaces (pyats-network show commands)
→ GAIT
5. Post-Change Network Verification
ServiceNow CR must be in Implement state
→ pyats_run_linux_command(host, "ifconfig") → verify interface state post-change
→ pyats_run_linux_command(host, "ip route show table all") → verify routes post-change
→ pyats_run_linux_command(host, "netstat -rn") → confirm routing table
→ Compare against pre-change baseline
→ GAIT
Parallel Operations
Run network checks across multiple Linux hosts concurrently:
# Host 1
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-01","command":"ifconfig"}'
# Host 2
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-02","command":"ifconfig"}'
# Host 3
PYATS_TESTBED_PATH=$PYATS_TESTBED_PATH python3 $MCP_CALL "${PYATS_PYTHON:-python3} -u $PYATS_MCP_SCRIPT" pyats_run_linux_command '{"device_name":"linux-host-03","command":"ifconfig"}'
Integration with Other Skills
| Skill | Integration |
|---|---|
| pyats-network | Correlate Linux host interfaces with network device interfaces — verify end-to-end connectivity |
| pyats-routing | Compare Linux host routes with network device routing tables (OSPF, BGP, EIGRP) |
| pyats-linux-system | System-level commands (ps, docker, ls) complement network-level inspection |
| pyats-linux-vmware | VMware ESXi host networking (vSwitch, vmkernel) via vim-cmd |
| pyats-parallel-ops | pCall pattern for fleet-wide Linux network audits |
| pyats-troubleshoot | Linux host network data feeds into OSI-layer troubleshooting |
| netbox-reconcile | Cross-reference ifconfig IP/MAC data against NetBox IPAM and DCIM records |
| nautobot-sot | Same as NetBox — validate Linux host IP addresses against Nautobot |
| subnet-calculator | Verify subnet masks and CIDR notation from ifconfig output |
| gait-session-tracking | Every Linux network command logged in GAIT |
Guardrails
- Always call
pyats_list_devicesfirst — verify Linux hosts exist in the testbed - Read-only commands only — ifconfig, ip route show, netstat, route are all read-only
- No configuration changes — never use
ip addr add,ip route add,ifconfig up/down, oriptablesvia this skill - Gate network changes behind ServiceNow — if extending to write operations, require a Change Request
- Cross-reference with SoT — always compare discovered IPs and routes against NetBox/Nautobot
- Record in GAIT — every command execution must be logged