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  • CCNA Articles

    IPv6 over IPv4 tunneling

    Wednesday, August 26th, 2009

    IPv6 over IPv4 tunneling allow access to the IPv6 Internet in absence of an IPv6 native access provider (Or interconnection between any IPv6 islands over an IPv4 infrastructure). Cisco routers support automatic (6to4, ISATAP) and configured IPv6 over IPv4 tunneling.

    Frame Relay Frequently Asked Questions

    Monday, August 24th, 2009

    In preparation of our CCNP exam, we want to make sure we cover the various concepts that we could see on our Cisco CCNP exam. So to assist you, below we will discuss Frame Relay Frequently Asked Questions. Introduction Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers […]

    OSPF Convergence

    Monday, August 24th, 2009

    Resiliency and redundancy to circuit failure is provided by the convergence capabilities of OSPF at layer 3. There are two components to OSPF routing convergence: detection of topology changes and recalculation of routes. Detection of topology changes is supported in two ways by OSPF. The first, and quickest, is a failure or change of status  […]

    IGP – Default Route Summary

    Monday, August 17th, 2009

    Default route RIP static route 0.0.0.0 to null 0, and the “network 0.0.0.0” command under the RIP process, static route 0.0.0.0 to null 0, and the “redistribute static” command under the RIP process, “default-information originate” command (advertises a default route even if a default route does not exist in the routing table / does not […]

    Frame-Relay – Things to Remember

    Saturday, August 15th, 2009

    When “encapsulation frame-relay” command is issued on an interface, the router will learn all the DLCIs associated with that interface via LMI updates. Then once an IP address is configured on the same interface, InARP request will be sent out on all the learned DLCIs. If the other end is also configured with an IP […]

    BGP – Things to Remember

    Friday, August 7th, 2009

    1. BGP uses TCP port 179 for transport. Router with the higher BGP router-id initiates BGP session from a random port. 2. The interface from which the BGP router ID is taken does not have to be running BGP. Any valid IP address can be used as BGP router-id, even an address that is not […]

    IGP – Things to Remember

    Thursday, August 6th, 2009

    1. Routing occurs by finding the longest match in the routing table and by recursing to the outgoing interface. 2. We can debug the transiting traffic by enabling the process switching. But we don’t need to turn on process switching for the router’s locally originated traffic or for the traffic destined for the router. 3. […]

    EIGRP – Things to Remember

    Tuesday, August 4th, 2009

    1. The IP header of an EIGRP packet specifies protocol number 88. 2. To establish neighbor relationship, the neighbors must be in the same IP subnet. While EIGRP supports secondary IP addresses and subnets, EIGRP sources its messages always from the address in the primary subnet, so the IP addresses of neighbors must be in […]

    OSPF – Things to Remember

    Monday, August 3rd, 2009

    1. The IP header of an OSPF packet specifies protocol number 89. 2. To establish OSPF neighbor adjacency, hello/dead timers, MTU (otherwise have to use "ip ospf mtu-ignore") must match. Unique router-id is also required. 3. Routers in stub area can only be adjacent with the routers in stubs or totally stubby area. Routers in […]