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CCNP Routing and Switching

Troubleshooting OSPF


We will be exploring some OSPF troubleshooting scenarios and see how to solve the problems. Trouble ticket #1: Passive interface We have two routers R2 and R3 configured as OSPF routers. The problem is that router R3 can not get routes ... Read More »



passive-interface in EIGRPif we set this command on an interface connected to an EIGRP neighbor, the neighborship will be down:We used to see two equal-cost routes to subnet (remember that EIGRP, like OSPF, support equal-cost load balancing): one through ... Read More »

Advanced OSPF Notes


Always check your OSPF neighbors. I had a problem injecting a default route into NSSA totally stub area, and I figured out it was a problem of OSPF network types.R3 and R4 were not already OSPF Neighbors. They are connected ... Read More »

Learning time and NTP on IOS

– There are two types of clocks: hardware clock and software clock.– The hardware clock has its own battery. When router shuts down, hardware calendar still works.– When we reboot router, the software clock synchronizes with hardware clock, even if ... Read More »

Route Redistribution


OSPF into EIGRP – On the ASBR, and after redistribution, there’s a change in EIGRP topology table. But no changes happen in the routing table: before redistribution: after redistribution: The change happens on the other routers, i.e. DSW1 and DSW2. ... Read More »

EIGRP notes


equal cost load balancingBy default: up to 4 equal cost routes in the routing table.Here we see that R4 receives two equal cost routes for network. It adds them to its topology table: and to the routing table to ... Read More »

NAT game


Here’s a simple topology to practice NAT, before playing with my real lab:– ensure that routing is configured between R0 and R2 (RIP for example)– I didn’t announce subnet. It should not be seen by R2. Static NAT a ... Read More »

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