TSHOOT: Troubleshooting & Maintaining Cisco (Part2 of Part2)

Cisco secure provides centralized command and control for all users' authentication, authorization, and accounting from a web-based graphical interface, with active reports shown in this snapshot.

Protect control plane security by ensuring control plane traffic is processed by the router's processor and preventing unauthorized participation in routing protocols and fhrp to avoid denial of service.

Identify control plane security features across devices, troubleshoot misconfigurations in routing protocols and FHRP authentication, and verify BPDU guard, loop guard, root guard, DHCP snooping, and DAI settings.

The show ip inspect sessions output shows that the trusted host 192.168.0.2 opened an http connection to an external web server 10.0.0.2.

Show how the show ip inspection session detail command displays SPRO configuration and in-session data, demonstrating ACL bypass that permits packets via existing inspection sessions rather than dynamic ACLs.

Demonstrates how an address translation error in a British router's IP tunnel disrupts VPN connectivity to headquarters while internet access remains available, illustrating branch-specific troubleshooting.

Start troubleshooting at the edge router with a bottom-up approach, using show ip interfaces brief to verify layer 1 and layer 2 status and that interfaces are up.

Identify a routing issue using the show ip command and verify a small branch office configuration with a static default route pointing to the wan interface next hop.

Display shows ACL 1 0 7 denies traffic from branch to headquarters, ensuring that branch-to-headquarters traffic is not subjected to NAT.

at the headquarters router, verify the vpn tunnel status and the branch router destination ip using the show crypto as a kmp command; both tunnels show active status.

Verify headquarters tunnel destination and fix HQ tunnel source (loopback 101, 10.208.202) instead of 10.200.222; identify typing error on the French router, and note HQ interface is down.

Investigate recursive routing issues where an interface goes down, the DRP stops advertising routes, and tunnels repeatedly establish and then drop after a few seconds despite resets.

Use show interface to verify the tunnel status on the branch interface and that the line protocol is down; confirm the source and destination align with the network diagram.

Replicate the issue by shutting HQ interfaces and bringing them up to trigger tunnel 0; observe adjacency message and tunnel 0 disabled by recursive routing as both sides go down.

Investigate how an acl denies ipsec in example 5, following a security auditor’s recommendations to adjust network policy after the change and ensure vpn connectivity for branch offices.

Identify that the ACL blocks IPsec and IKE traffic due to missing statements; adjust access lists to permit IPsec protocols and UDP port 500 to restore these connections.

Explore how security features affect router and switch operation across the management, control, and data planes, including management duties and protocols like telnet and ssh.

Explore web based management access and device managers such as Cisco configuration professional and security device manager, using HTTP or HTTPS to access read or read-write operational parameters.

Data plane security uses IPsec and RPF on routers; troubleshoot branch connectivity by checking firewalls/ACLs, overlapping subnets, asymmetric routing, and VPN high availability with HSR.

Review chapter 5 focuses on maintaining and troubleshooting routing solutions, emphasizing network layer connectivity and in-depth troubleshooting of EIGRP, OSPF, and BGP.

Cover key topics from chapter 8 on troubleshooting converged networks, highlighting wireless integration issues at the wireless-to-wired boundary, including filters blocking traffic, wireless QoS, PoE short issues, and trunk issues.

Review chapter 9 on the control plane and identify issues such as routing protocols, stp, bpdu guard, bpdu filter, loop guard, dhcp snooping, dynamic arp inspection, and control plane policy.

Map complex integrated networks and understand how protocols and technologies deliver enterprise services. Use a diagnostic process to identify and resolve problems with a solution or workaround.

Develop a practical troubleshooting approach by understanding key network technologies and their interactions, maintain a daily log of notes and documentation, and identify root causes before applying temporary fixes.

Apply top-down, bottom-up, or hybrid troubleshooting approaches, document discoveries, and follow a structured workflow from defining the problem to testing hypotheses and iterating.

Apply a seven-step troubleshooting workflow to identify problems, gather information, analyze data, eliminate causes, formulate hypotheses, implement and test solutions, and document changes for security policy compliance.

Demonstrates troubleshooting concepts for routing and switching on a layer 3 switch, covering config, hostname, service password encryption, motd banner, ip routing, domain name, and host table setup on MSW1.