6th. TCP/IP routing protocol fault handling
First, the default gateway
When the destination address of the package is not in the router's routing table, such as when the router is configured with a default gateway, it is forwarded to the default gateway or discarded.
show IP route; View the default gateway for Cisco routers
Second, static and dynamic routing
Third, processing k_protocal/04937.htm "target=" _blank ">rip fault
RIP is the distance vector routing protocol, and the metric is the hop count. RIP has a maximum hop count of 15 and is unreachable if the number of hops to the target exceeds 15.
RIP V1 is a class routing protocol, RIP V2 is a non-categorical routing protocol that supports CIDR, route induction, VLSM, and sends routing updates using multicast (224.0.0.9).
RIP-related show commands:
show ip route rip; display RIP routing table only
Show IP route, display all IP routing tables
show IP interface; Display IP interface configuration
Show Running-config
Debug IP RIP events;
Common RIP failures: RIP version inconsistencies, RIP using UDP broadcast updates
Iv. Handling of IGRP failures
IGRP is a Cisco private routing protocol, a distance vector protocol. IGRP's metrics can be based on five features: bandwidth, latency, load, reliability, MTU, and only bandwidth and latency are used by default.
IGRP-related Show commands:
show ip route igrp; display IGRP routing table
Debug IP IGRP events;
Debug IP IGRP transactions;
Common IGRP Failures: Access list, incorrect configuration, line down to neighboring routers
V. Handling EIGRP Failures
EIGRP is a link-state protocol and a distance-vector hybrid protocol, which is a Cisco private routing protocol. EIGRP uses the multicast address 224.0.0.10 to send routing updates, using the dual algorithm to calculate routes. The metrics for EIGRP can be based on bandwidth, latency, load, reliability, MTU, and only bandwidth and latency are used by default.
EIGRP uses 3 kinds of databases: the routing database, the topology database, and the neighboring router database.
EIGRP-related Show commands:
Show Running-config
Show IP route
Show ip Route eigrp, show EIGRP routes only
show IP EIGRP interface; Display peer information for this interface
show ip eigrp neighbors; display all EIGRP neighbors and their information
show ip eigrp topology; display the contents of the EIGRP topology table
show ip EIGRP traffic; show the induction of EIGRP routing statistics
show IP EIGRP events; display the most recent EIGRP protocol event record
EIGRP-related DEBUG commands:
Debug IP eigrp as number
Debug IP eigrp Neighbor
Debug IP eigrp Notifications
Debug IP EIGRP Summary
Debug IP EIGRP
Common EIGRP failures: missing neighbors, default gateways, and so on, old iOS routing, stuck in active.
When dealing with EIGRP failures, first use show IP eigrp neighbors to view all neighboring routers, then use show ip route gigrp to view the router's routing table, and then use show IP eigrp topology to view the topology table of the router. You can also use show IP EIGRP traffic to see if routing updates are being sent.
VI. handling of OSPF failures
OSPF is a link-state protocol that maintains 3 databases: adjacent databases, a topology database, and a routing table.
OSPF-related Show commands:
Show Running-config
Show IP route
show IP route OSPF; show only OSPF routes
show ip OSPF process-id; Display information related to a specific process ID
show ip OSPF; display OSPF-related information
show ip OSPF border-routers; display border router
show ip OSPF database;
show ip OSPF interface; display OSPF information on the specified interface
show ip OSPF neighbor; display OSPF adjacency information
show ip OSPF request-list; Show Link status request list
show ip OSPF summary-address; show redistribution information for inductive routes
show ip OSPF virtual-links; show 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 failure: OSPF has no more than 100 routers per area, no more than 700 routers in the entire network, and improper wildcard mask configuration;
Vii. Handling BGP Failures
The key configuration for BGP (including IBGP and EBGP) is neighbor relationships, and BGP uses TCP to establish neighboring relationships.
BGP-related Show commands:
show ip bgp; shows the routes learned by BGP
Show ip BGP Network, displaying BGP information for a specific network
show IP neighbors; display BGP neighbor information
show ip BGP peer-group; display BGP treats group information
show ip BGP summary; shows the generalization of all BGP connections
show ip route BGP; show 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 failures:
Viii. re-release routing protocol
Ix. TCP/IP symptoms and Causes
Cause of symptoms
Local host cannot communicate with remote Host 1) DNS is not working properly 2) No route to remote host 3) missing default gateway 4) Administrative deny (ACL)
An application does not work 1) management Deny (ACL) 2) The network is not configured properly to process the application
Startup failure 1) The BOOTP server does not have a MAC address entity 2) Missing IP helper-address3) ACL4) modify Nic or MAC address 5) Duplicate IP address 6) Unhealthy IP configuration
Cannot ping remote host 1) ACL2) No route to remote host 3) not set default gateway 4) remote host down
Routing protocol 1 not configured correctly 2) Release List 3) passive interface 4) No advertised routed neighbor 5) routing protocol version inconsistency 6) Neighbor relationship not established
adjacency relationship not established 1) incorrect routing protocol configuration 2) incorrect IP configuration 3) Not configured network or Neighbor statement 4) Hello interval inconsistent 5) inconsistent area ID
High CPU Utilization 1) unstable routing update 2) process overloading without shutting down DEBUG3
Route trigger Active Mode 1) inconsistent interval 2) hardware problem 3) unstable link
X. TCP/IP Symptoms and action plans
Action Plan on issues
DNS is not working properly 1) Configure DNS host configuration and DNS servers that can use Nslookup to verify the work of the DNS server
No route to the remote host 1) Check the default gateway with Ipconfig/all 2) Use the show IP route to see if the route 3) if there is no such route, see if there is a default gateway 4 with the show IP route, if there is a gateway, check the next hop to the target, or fix the problem if there is no gateway
ACLs have separate problems associated with ACLs, and ACLs must be parsed, or overridden, and applied.
Network is not configured to process applications view router configuration
Booting failure 1) View DHCP or BOOTP server and see if there is a failure machine for Mac entity 2) use debug IP UDP checksum to receive packets from the host 3) verify helper-address correct configuration 4) to see if the ACL disables the package
Missing Route 1) Check the routes learned on the 1th router with show IP route 2) Verify that the neighboring router 3) has the correct routing network and neighbor statement 4) to OSPF, the checksum wildcard mask 5) checks the distribute applied to the interface LIST6) Verify the IP configuration of the neighbor 7) Verify that the route is re-released if the route is republished, validate the measure 8)
Does not constitute an adjacent relationship 1) Use the show IP protocol Neighbors list of adjacent relationships 2) to view the protocol configuration that does not constitute an adjacent relationship 3) Check the network statement in the routing configuration 4) with the show IP protocol/ Interface viewing specific interface information, such as the Hello interval
From for notes (Wiz)
6th. TCP/IP routing protocol fault handling
