Some things I know I will forget again, lots of bullet points, like the ‘in a can’ posts


Above is the following topology I have created, all interfaces on the NBMA are on the /24 subnet and the LAN section will be /24 with all interfaces aside from loopbacks having the router # as the 4th octet IP address.

Upon going through even basic EIGRP setup videos over an NMBA network, there were some concepts I let slip, so I’ll kind of be doing a point by point here of those for myself:

  • EIGRP Hub and Spoke will not advertise routes due to Split-Horizon, you can flat out disabled on the Hub on the interface level with “no ip split eigrp (AS #), may drop adjacencies. You can also break the Hub’s interface up into sub-interfaces, I will try to get the info on making sub-int’s posted
  • For OSPF to form adjacences over an NBMA, you need ‘neighbor xx.xx.xx.xx’ address in router config mode, EIGRP DOES NOT REQUIRE NEIGHBOR STATEMENTS ON THE HUB(S) IN HUB AND SPOKE NETWORKS, ONLY OSPF
  • EIGRP Route table shows route paths being used from the Topology table as Successor routes, Topology table shows Successor and Feasible Successor paths, Neighbor tables shows random info about neighbors (peer addy, uptime, etc)
  • DUAL is the algorithm that runs throughout the EIGRP network, querying for a loop-free path to a destination network, if no path is found route goes ‘Stuck in Active’
  • By default EIGRP load balances up to 4 paths to a destination if their FD’s match, unless you use the Variance command in router config to multiply the acceptable FD for a route to be brought into the route table, but **WILL NOT change the FD #”
  • “sh ip eigrp int detail” will give a lot of good output, including authentication info
  • Hello / Hold timers set on interface, “ip hello / hold eigrp (AS #) #”
  • Only need to agree on AS # and K Values to form adjacency
  • Feasibility Condition = Is the FS’s Advertised Distance lower than the Successors than the Feasible distance that the successor – It is that easy.

I only slipped a bit getting the spokes (R2, R3 to see eachother’s loopbacks of and, and caught myself already missing an important part of the configuration – turning off split horizon on the Hub’s interface in the EIGRP domain. I know I have done this before by making the single physical interface into multiple sub-interfaces but I cannot recall how, but I assume along the way to certification I’ll figure out why. Next will be playing with advanced stuff like Variance, K Weights, and Authentication before moving onto OSPF.

I would like to wrap up getting my CCNP before I have to deal with moving in July / August so June is my unofficial deadline for everything to be done. I am thinking ROUTE by end of February, Switch by end of May, and TSHOOT somewhere in June.

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