Category Archives: Routing

Troubleshoot NAT

Definitions NAT Types Static NAT — A one-to-one mapping of private to public IP addresses, best used for a device that needs access from outside the AS. Dynamic NAT — A dynamic one-to-one mapping between private and public IP addresses, … Continue reading

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Troubleshooting Spanning Tree Protocol

Spanning Tree Protocol Basics: In a layer 2 environment with no routing, active redundant paths are neither allowed no desirable, because the can cause loops. Because a switch only segments collision domains it does not segment broadcast domains. STP helps … Continue reading

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Troubleshoot Router Performance

There are three general causes of router performance issues: 1. High CPU load 2. Router packet switching mode 3. Excessive memory use Processes that can be a cause of high CPU load: • ARP Input process — Heavy traffic load … Continue reading

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Troubleshoot BGP

2010-04-13 16:07:12 Troubleshoot BGP BGP is a path-vector routing protocol. Routes are tracked in terms of the AS they pass through, and routers avoid loops by rejecting routes that have already passed through their AS. Definitions Synchronization — Before iBGP … Continue reading

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Troubleshoot OSPF

My notes for EIGRP felt like I was just regurgitating the Key Points from the book. So with OSPF I read the book and looked at the command output, then decided to copy my notes from the BSCI and edit … Continue reading

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Layer 3 Troubleshooting

Cisco Express Frowarding (CEF) The two main components of CEF are the forwarding information base (FIB) and the adjacency table. IP routing table is maintained by a router’s control plane. CEF operates in the data plane. Forwarding Information Base (FIB) … Continue reading

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Cisco Express Forwarding and Layer 2 to Layer 3

2010-04-04 14:21:36 Cisco Express Forwarding (CEF) The two main components of CEF are the forwarding information base (FIB) and the adjacency table. IP routing table is maintained by a router’s control plane. CEF operates in the data plane. Forwarding Information … Continue reading

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Layer 3 Switch Troubleshooting

The big topics of this chapter include HSRP, VRRP, GLBP, TCAM and the port error table. I broke out my notes from the BCMSN and I’ll summarize each topic from them, then move into the troubleshooting of each protocol. Hot … Continue reading

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Making the Transition

How do you know you have crossed over from a sysadmin to a network admin? When you log on to a Linux server and type “en.” There is a story here. I used to login to a router or switch … Continue reading

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Network Maintenance

I am going to admit that I have not been studying for the TSHOOT exam very diligently. In my mind it is a topic that we deal with on a daily basis and what could the book teach me. (sarcasm) … Continue reading

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