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First, the complexity of the network
General networks include routing, dialing, switching, video, WAN (ISDN, Frame Relay, ATM, ...), LAN, VLAN,...
Second, the fault handling model
1. Define the Problem
Describe the symptoms and potential causes of the failure in detail and accurately
2. Collect detailed information (Gather Facts) R>Information ">RIP failure
RIP is a distance vector routing protocol and the metric is the hop count. The maximum number of hops for RIP is 15. If the number of hops to the target exceeds 15, it is unreachable.
RIP V1 is a classful routing protocol, RIP V2 is a non-categorical routing protocol, supports CIDR, route induction, VLSM, and uses multicast (224.0.0.9) to send routing updates.
RIP related show command:
Show IP route rip; display only RIP routing table
Show IP route; show all IP routing tables
Show IP interface; display IP interface configuration
Show running-config
Debug IP rip events ;
Common RIP failures: RIP versions are inconsistent, RIP uses UDP broadcast updates
Fourth, dealing with IGRP failure
IGRP is a Cisco-specific routing protocol, a distance vector protocol. The IGRP metric can be based on five elements: bandwidth, latency, load, reliability, MTU, and only bandwidth and latency are used by default.
IGRP related show command:
Show IP route igrp; display IGRP routing table
Debug IP igrp events ;
Debug IP igrp transactions ;
Common IGRP failures: access lists, incorrect configuration, line down to neighboring routers
Fifth, deal with EIGRP failure
EIGRP is a link state protocol and distance vector hybrid protocol and is a CISCO dedicated routing protocol. EIGRP uses the multicast address 224.0.0.10 to send routing updates and the DUAL algorithm to calculate routes. EIGRP metrics can be based on bandwidth, latency, load, reliability, MTU, and only bandwidth and latency are used by default.
EIGRP uses three types of databases: routing databases, topology databases, and neighboring router databases.
EIGRP related show commands:
Show running-config
Show IP route
Show IP route eigrp; only show EIGRP routes
Show ip eigrp interface; displays the peer information of the interface
Show ip eigrp neighbors; Show all EIGRP neighbors and their information
Show ip eigrp topology; shows the contents of the EIGRP topology table
Show ip eigrp traffic; shows the induction of EIGRP routing statistics
Show ip eigrp events; show recent EIGRP protocol event records
EIGRP related debug commands:
Debug IP eigrp as
Debug IP eigrp neighbor
Debug IP eigrp notifications
Debug IP eigrp summary
Debug IP eigrp
Common EIGRP faults: loss of the neighbor relationship, default gateway, etc., routing of old version IOS, stuck in active.
When processing EIGRP faults, first use the show ip eigrp neighbors to view all neighboring routers, then use show ip route gigrp to view the router's routing table, then use show ip eigrp topology to view the router's topology table, or use show ip eigrp traffic to view Whether the route update is sent.
Sixth, dealing with OSPF faults
OSPF is a link state protocol that maintains three databases: a neighboring database, a topology database, and a routing table.
OSPF related show command:
Show running-config
Show IP route
Show IP route ospf; only shows OSPF routes
Show IP OSPF process-id; displays information related to a specific process ID
Show IP OSPF; Display OSPF related information
Show IP OSPF border-routers; show border router
Show ip ospf database; display OSPF inductive database
Show ip ospf interface; Display OSPF information on the specified interface
Show IP OSPF neighbor; display OSPF neighbor information
Show IP OSPF request-list; display link status request list
Show IP OSPF summary-address; display report information for inductive routes
Show IP OSPF virtual-links; display virtual link information
Show IP interface; display the IP settings of the interface
OSPF related debug commands:
Debug IP OSPF adj ;
Debug IP ospf events
Debug IP ospf flood
Debug IP OSPF LSA-generation
Debug IP OSPF packet
Debug IP ospf retransmission
Debug IP OSPF SPF
Debug IP ospf tree
Common OSPF faults: OSPF does not exceed 100 routers per domain, and the entire network does not exceed 700 routers; the wildcard mask is improperly configured;
Seven, dealing with BGP failure
The key configuration of BGP (including IBGP and EBGP) is the neighbor relationship. BGP uses TCP to establish a neighbor relationship.
BGP related show command:
Show IP BGP; shows the routes learned by BGP
Show IP BGP network; Display BGP information for a specific network
Show IP neighbors; Display BGP neighbor information
Show IP BGP peer-group; Display BGP treatment group information
Show IP BGP summary; shows the induction of all BGP connections
Show IP route BGP; Display BGP routing table
BGP related debug commands:
Debug IP BGP 192.1.1.1 updates
Debug IP BGP dampening
Debug IP BGP events
Debug IP BGP keepalives
Debug IP BGP updates
Typical BGP failure:
Eight, re-release routing protocol
Nine, TCP / IP symptoms and causes
Symptom cause
The local host cannot communicate with the remote host 1) The DNS is not working properly 2) There is no route to the remote host 3) The default gateway is missing 4) Management Rejection (ACL)
An application is not working properly 1) Management Denial (ACL) 2) The network is not properly configured to process the application
Startup failure 1) BootP server has no MAC address entity 2) Missing IP helper-address3) ACL4) Modify NIC or MAC address 5) Duplicate IP address 6) Unusual IP configuration
Cannot ping remote host 1) ACL2) No route to remote host 3) No default gateway set 4) Remote host down
Missing route 1) Routing protocol not configured correctly 2) Release list 3) Passive interface 4) Neighbors without advertised routes 5) Inconsistent routing protocol version 6) Neighbor relationship not established
Adjacency is not established 1) Incorrect routing protocol configuration 2) Incorrect IP configuration 3) Network or neighbor statement is not configured 4) Hello interval is inconsistent 5) Inconsistent area ID
High CPU utilization 1) Unstable routing updates 2) No debug3 shutdown) Process is too heavy
Route triggered active mode 1) Inconsistent interval 2) Hardware problem 3) Unstable link
X. TCP/IP Symptoms and Action Plan
Problem action plan
DNS does not work properly 1) Configure the DNS host configuration and DNS server, you can use nslookup to verify the DNS server's work.
There is no route to the remote host 1) Check the default gateway with ipconfig /all 2) Use show ip route to check whether the corresponding route 3) If there is no such route, use show ip route to check if there is a default gateway 4) If there is a gateway, check Next hop to the target; if there is no gateway, fix the problem
ACLs have separate issues related to ACLs, which must be analyzed for ACLs, or rewritten ACLs and applied.
The network is not configured to process applications View router configuration
Booting fails 1) Check the DHCP or BootP server and check if there is a MAC entity of the faulty machine. 2) Use debug IP UDP to check the packets received from the host. 3) Verify that the helper-address is correctly configured. 4) Check whether the ACL disables the package.
Missing route 1) Use show ip route on the first router to view the learned routes 2) Verify neighboring routers 3) Have correct routing network and neighbor statements 4) Verify OSPF, check wildcard mask 5) Check Apply to the distribution list6 on the interface to verify the neighbor's IP configuration. 7) If the route is re-issued, verify the metric 8) Verify that the route is re-issued normally.
Does not constitute an adjacent relationship 1) Use the show IP protocol neighbors list to form a neighbor relationship 2) View the protocol configuration that does not constitute a neighbor relationship 3) Check the network statement in the route configuration 4) Use the show IP protocol/interface to view the specific Interface information, such as Hello interval.
