diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index 5adc0f6..e7f4cf9 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -71,3 +71,4 @@
 - [附录一：华为交换机端口镜像](port-mirroring.md)
 - [附录二：IPv6地址空间](IPv6_address_space.md)
 - [附录三：GNS3简介](GNS3_tutorial.md)
+- [附录三：网络故障排除](network_troubleshooting.md)
diff --git a/src/network_troubleshooting.md b/src/network_troubleshooting.md
new file mode 100644
index 0000000..2091f4e
--- /dev/null
+++ b/src/network_troubleshooting.md
@@ -0,0 +1,76 @@
+# 网络故障排除
+
+本文记录网络故障排除，以备今后遇到同样问题时，快速解决。
+
+
+## 光模块起不来的问题
+
+
+光模块起不来，通常是因为所使用的光模块，与光纤不匹配的原因造成。其中，多模光模块使用 810nm 波长的激光，而单模光模块则使用 1310nm 波长的激光。有关单模与多模的区别，请参考：[Fiber Optic Cable Types: Single Mode vs Multimode Fiber Cable](https://community.fs.com/article/single-mode-cabling-cost-vs-multimode-cabling-cost.html)。排查此问题的三个命令（H3C）:
+
+
+- `display transceiver interface Ten-GigabitEthernet 1/0/52`
+
+
+输出：
+
+
+```console
+[xfoss-com-core]display transceiver interface Ten-GigabitEthernet 1/0/52
+Ten-GigabitEthernet1/0/52 transceiver information:
+  Transceiver Type              : 10G_BASE_SR_SFP
+  Connector Type                : LC
+  Wavelength(nm)                : 850
+  Transfer Distance(m)          : 80(OM2),30(OM1),300(OM3)
+  Digital Diagnostic Monitoring : YES
+  Vendor Name                   : XFOSS-COM
+  Vendor Part Number            : SFPXG-850C-D30
+  Part Number                   : SFPXG-850C-D30
+  Serial Number                 : 012345678901
+```
+
+- `display transceiver manuinfo interface Ten-GigabitEthernet 1/0/52`
+
+
+输出：
+
+
+```console
+[xfoss-com-core]display transceiver manuinfo interface Ten-GigabitEthernet 1/0/51
+Ten-GigabitEthernet1/0/51 transceiver manufacture information:
+  Manu. Serial Number : 01234567890123456789
+  Manufacturing Date  : 2017-04-01
+  Vendor Name         : XFOSS-COM
+```
+
+
+- `display transceiver diagnosis interface Ten-GigabitEthernet 1/0/51` 
+
+输出：
+
+
+```console
+[xfoss-com-core]display transceiver diagnosis interface Ten-GigabitEthernet 1/0/51
+Ten-GigabitEthernet1/0/51 transceiver diagnostic information:
+  Current diagnostic parameters:
+    Temp.(C) Voltage(V)  Bias(mA)  RX power(dBm)  TX power(dBm)
+    42         3.41        6.42      -2.55          -2.71
+  Alarm thresholds:
+          Temp.(C) Voltage(V)  Bias(mA)  RX power(dBm)  TX power(dBm)
+    High  80         3.60        15.00     0.00           0.00
+    Low   -15        3.00        0.00      -10.90         -8.30
+```
+
+
+- `display transceiver alarm interface Ten-GigabitEthernet 1/0/52`
+
+
+输出：
+
+
+```console
+[xfoss-com-core]display transceiver alarm interface Ten-GigabitEthernet 1/0/52
+Ten-GigabitEthernet1/0/52 transceiver current alarm information:
+  RX power low
+  RX signal loss
+```