Peer on Aaron's Worthless Words

EIGRP and OSPF - Are We Connected?

Fri, 27 Jun 2014 00:00:00 +0000

For both OSPF and EIGRP routers to become neighbors, their interface’s primary IP address must be on the same subnet. That statement is true. There is a difference in the definition of “same subnet”, though.

In OSPF, both routers have to be configured to be on the same subnet with the same mask or else they won’t neighbor up. When an hello packet is sent, the subnet mask is sent embedded in there. The router does a quick look to be sure the subnets are defined the same way on both ends. If everything doesn’t match, they don’t neighbor. Here’s a Wireshark screenshot to show you the OSPF hello. Note: See edit below.

BGP Notes - Neighbor States

Tue, 07 Jun 2011 00:00:00 +0000

Corrections appreciated.

Idle : There is no relationship, but the router sends out a TCP SYN to the neighbor to get the ball rolling.

Idle (admin) : The neighbor is admined down.

Connect : The router is waiting for the TCP connection to finish. If the TCP connection finishes, the router sends an open and transitions to OpenSent. If it times out, it transitions to Active.

Active : The router tries Cialis to initiate a TCP connection. If the TCP connection finishes, the router sends an open and transitions to OpenSent.

IIUC Notes - Inbound Dial Peer Matching

Wed, 19 Jan 2011 00:00:00 +0000

More IIUC notes. As always, feel free to correct as needed.

To match inbound calls to a dial peer, CME (and CUCM?) uses the following steps.

Match DNIS (the dialed number) with the incoming called-address config in the dial peer
Match the ANI (the calling number or caller ID) with the answer-address config in the dial peer
Match the ANI with the destination-pattern config in the dial peer
Match an incoming POTS call to the port config in the dial peer
Match dial peer 0

Matching dial peer 0 is bad, and it took me an inquiry on Twitter and a buddy to realize why. Here are a few highlights as to why. I believe the full scope of the badness of dial peer 0 is really beyond the IIUC exam.