CCNP Troubleshooting!!

Common Routing Problem:

Common causes for routes not being installed in the routing table.

-missing or incorrect network or neighbor statement

-Layer 1 and Layer 2 down

-Distribute-list in/out blocking (sender/receiver)

-Access list blocking

-Advertised network Interface is down

-Passive interface

RIP:

-incompatible RIP version types

-a mismatched authentication key

-RIP hop count limit

-discontinuous networks

Troubleshooting eigrp

-Mismatched k values

 -mismatched AS numbers

-stuck in Active

-Duplicate Router ID’s

Common EIGRP Errors:

-Primary route gone and no feasible successor

-neighbor is not in common subnet

-EIGRP thinks it knows more routes for a given network than actually exist

-EIGRP internal error

-EIGRP attempted to install a route to the destination and failed, most commonly because of the existence of route with a better administrative distance.

-Interface receives an EIGRP hello packet and the router attempts to associate the packet with a DUAL descriptor block for that interface,  but it does not find that matches

-Router threads a topology table entry as poison in reply to an update, but while the router is building the packet that contains the poison reverse, the router realizes that it does not need to send it.

Troubleshooting OSPF neighbor:

Possible reasons for stuck in the state.

-No information from neighbor

-hello sent – no reply

-1 side blocking hello packet

-normal on broadcast networks

- access list, MTU size

-neighbor sending bad packet.

Adjacencies not coming up:

-layer 2 down

-ospf  not enabled

-passive interface used

-mismatched subnets

-mismatched hellos/dead interval

-mismatched authentication

-mismatched area ids

-mismatched area types

Troubleshooting OSPF – missing routes

Routing protocols

-redistribution

Stub vs NSSA vs Totally Stub

-default routes and summarization

Route filters

-access-list

Virtual links

OSPF mismatched parameters:

-mismatched hello/dead interval

-mismatched authentication

-mismatched area ids

-mismatched area types

Common BGP neighbor problems:

Directly connected EBGP neighbors not initializing

– L2 is down or incorrect neighbor IP address

Non-directly connected EBGP neighbors not initializing

-route to the non-directly connected peer address is missing  from the routing table

-ebgp-multihop command is missing

-update-source interface command is missing.

IBGP neighbors not initializing