Segment Routing Troubleshooting แก้ปัญหา — วิเคราะห์และแก้ไข SR Network | SiamCafe Blog

Segment Routing

Segment Routing Troubleshooting SR-MPLS SRv6 ISIS OSPF Traffic Engineering Prefix SID Adjacency SID SRGB Label Policy Fast Reroute Service Chaining

SR-MPLS Troubleshooting

# === SR-MPLS Troubleshooting Commands ===

# Step 1: Check IGP Adjacency
# show isis neighbors
# show ospf neighbor
# show isis database detail
# show isis segment-routing

# Step 2: Verify SRGB (Segment Routing Global Block)
# show segment-routing mpls state
# show isis segment-routing global-block
# ! Default SRGB: 16000-23999
# ! All routers in domain MUST have same SRGB

# Step 3: Check Prefix SID
# show isis segment-routing prefix-sid-map
# show isis route detail
# ! Verify Prefix SID is unique per prefix
# ! No SID conflicts across the network

# Step 4: Verify Label Forwarding
# show mpls forwarding-table
# show mpls forwarding-table labels 16001
# ! Check SWAP/PUSH/POP actions

# Step 5: Check SR Policy
# show segment-routing traffic-eng policy all
# show segment-routing traffic-eng policy name SR-POLICY-1
# show segment-routing traffic-eng forwarding

# Step 6: End-to-end Verification
# traceroute mpls segment-routing 10.0.0.1/32
# ping mpls segment-routing 10.0.0.1/32
# traceroute sr-mpls 16001 16002 16003

# IOS-XR Configuration
# router isis CORE
# address-family ipv4 unicast
# segment-routing mpls
# interface Loopback0
# address-family ipv4 unicast
# prefix-sid index 1
# interface GigabitEthernet0/0/0/0
# address-family ipv4 unicast
# metric 10
# segment-routing
# global-block 16000 23999

from dataclasses import dataclass

@dataclass
class SRIssue:
 issue: str
 symptom: str
 cause: str
 command: str
 fix: str

issues = [
 SRIssue("No Prefix SID", "Label not in forwarding table", "SID not configured on Loopback", "show isis segment-routing prefix-sid", "Configure prefix-sid index under Loopback"),
 SRIssue("SRGB Mismatch", "Label collision wrong forwarding", "Different SRGB on routers", "show segment-routing mpls state", "Align SRGB on all routers"),
 SRIssue("SID Conflict", "Duplicate SID two prefixes", "Same SID index on different routers", "show isis segment-routing prefix-sid-map", "Assign unique SID per prefix"),
 SRIssue("IGP Not Converged", "SR labels not learned", "ISIS/OSPF adjacency down", "show isis neighbors", "Fix IGP adjacency first"),
 SRIssue("SR Policy Down", "Traffic not following TE path", "Segment list invalid or next-hop unreachable", "show sr traffic-eng policy", "Fix segment list or path"),
]

print("=== Common SR Issues ===")
for i in issues:
 print(f" [{i.issue}]")
 print(f" Symptom: {i.symptom}")
 print(f" Cause: {i.cause}")
 print(f" Command: {i.command}")
 print(f" Fix: {i.fix}")

SRv6 Troubleshooting

# === SRv6 Troubleshooting ===

# SRv6 Locator and SID
# show segment-routing srv6 sid
# show segment-routing srv6 locator
# show segment-routing srv6 manager

# SRv6 Configuration
# segment-routing
# srv6
# locators
# locator MAIN
# micro-segment behavior unode psp-usd
# prefix fc00:0:1::/48

# SRv6 Functions
# fc00:0:1:: — End (endpoint)
# fc00:0:1:1:: — End.X (L3 cross-connect)
# fc00:0:1:40:: — End.DT4 (decap to IPv4 VRF)
# fc00:0:1:60:: — End.DT6 (decap to IPv6 VRF)

# Verify SRv6 forwarding
# show cef ipv6 fc00:0:1::/48
# show route ipv6 fc00:0:1::/48
# traceroute ipv6 fc00:0:2::1 source fc00:0:1::1

# SRv6 VPN (L3VPN over SRv6)
# vrf CUSTOMER-A
# address-family ipv4 unicast
# import route-target 100:1
# export route-target 100:1
# router bgp 65000
# vrf CUSTOMER-A
# address-family ipv4 unicast
# segment-routing srv6
# locator MAIN
# alloc mode per-vrf

@dataclass
class SRv6Function:
 function_name: str
 behavior: str
 use_case: str
 sid_example: str

functions = [
 SRv6Function("End", "Endpoint SRH processing", "Transit node", "fc00:0:1::"),
 SRv6Function("End.X", "L3 cross-connect to next-hop", "Adjacency SID", "fc00:0:1:1::"),
 SRv6Function("End.DT4", "Decap and lookup IPv4 VRF", "L3VPN PE", "fc00:0:1:40::"),
 SRv6Function("End.DT6", "Decap and lookup IPv6 VRF", "L3VPN PE IPv6", "fc00:0:1:60::"),
 SRv6Function("End.DX4", "Decap and forward IPv4", "Per-CE VPN", "fc00:0:1:41::"),
 SRv6Function("End.B6.Encaps", "Encap with new SRH", "TE Policy binding", "fc00:0:1:b6::"),
 SRv6Function("H.Encaps", "Headend encap SRH", "SR Policy headend", "N/A (headend)"),
]

print("\n=== SRv6 Functions ===")
for f in functions:
 print(f" [{f.function_name}] {f.behavior}")
 print(f" Use Case: {f.use_case} | SID: {f.sid_example}")

Traffic Engineering

# === SR Traffic Engineering ===

# SR Policy Configuration
# segment-routing
# traffic-eng
# policy SR-LOW-LATENCY
# color 10 end-point ipv4 10.0.0.5
# candidate-paths
# preference 100
# explicit segment-list LOW-LAT-PATH
# constraints
# segments
# dataplane mpls
# segment-list LOW-LAT-PATH
# index 10 mpls label 16002
# index 20 mpls label 16004
# index 30 mpls label 16005

# Flex-Algo Configuration
# router isis CORE
# flex-algo 128
# metric-type delay
# advertise-definition
# interface GigabitEthernet0/0/0/0
# address-family ipv4 unicast
# metric 10
# performance-measurement
# interface GigabitEthernet0/0/0/0
# delay-measurement

# On-Demand Next-hop (ODN)
# segment-routing
# traffic-eng
# on-demand color 10
# dynamic
# pcep
# metric type latency

@dataclass
class TEPolicy:
 name: str
 policy_type: str
 constraint: str
 path_type: str
 use_case: str
 status: str

policies = [
 TEPolicy("LOW-LATENCY", "Color 10", "Min Latency", "Dynamic PCEP", "VoIP Video", "Active"),
 TEPolicy("HIGH-BW", "Color 20", "Min Available BW", "Dynamic PCEP", "Backup Streaming", "Active"),
 TEPolicy("EXPLICIT-DC", "Color 30", "Explicit Path", "Static Segment List", "DC Interconnect", "Active"),
 TEPolicy("FLEX-ALGO-128", "Flex-Algo", "Delay Metric", "IGP Algo 128", "Latency-sensitive", "Active"),
 TEPolicy("DISJOINT", "Color 40", "Path Disjointness", "PCE Computed", "Redundancy", "Standby"),
]

print("SR-TE Policies:")
for p in policies:
 print(f" [{p.name}] Type: {p.policy_type} | Status: {p.status}")
 print(f" Constraint: {p.constraint} | Path: {p.path_type}")
 print(f" Use Case: {p.use_case}")

monitoring = {
 "IGP Adjacency": "show isis neighbors | include Up",
 "SR Labels": "show mpls forwarding-table | count",
 "SR Policy Status": "show sr traffic-eng policy all | include Active",
 "FRR Coverage": "show isis fast-reroute",
 "Link Delay": "show performance-measurement interfaces",
 "BFD Sessions": "show bfd session | include Up",
}

print(f"\n\nMonitoring Commands:")
for k, v in monitoring.items():
 print(f" [{k}]: {v}")

เคล็ดลับ

• SRGB: ตรวจ SRGB ทุก Router ต้องตรงกัน ก่อน Troubleshoot อื่น
• Unique SID: ทุก Prefix SID ต้อง Unique ทั้ง Domain
• IGP First: แก้ IGP Adjacency ก่อน แล้ว SR จะตามมา
• Traceroute: ใช้ traceroute mpls sr ตรวจ Label Path
• Flex-Algo: ใช้ Flex-Algo สำหรับ Multiple Topology ง่ายกว่า TE Policy

Segment Routing คืออะไร

Network Architecture Segment SID Label SR-MPLS SRv6 IGP ISIS OSPF ไม่ต้อง LDP RSVP-TE Traffic Engineering Fast Reroute Service Chaining