Reflexive ACLs Limitation

Remember that traffic originated from a router that has a reflexive ACL applied will not be evaluated. You need to explicitly permit the necessary traffic (routing protocol traffic, telnet, ICMP, etc.) on the inbound list.

Useful Grep #1

To help with seeing subnet mask issues:

Rack1R6#sh int ! i is up!Internet
Ethernet0/0 is up, line protocol is up
Internet address is 141.1.36.6/24
Ethernet0/1 is up, line protocol is up
Internet address is 141.1.6.6/24
Serial1/0 is up, line protocol is up
Internet address is 54.1.1.6/24
Loopback0 is up, line protocol is up
Internet address is 150.1.6.6/24

OSPF - No Virtual Link across Stub Area

A virtual-link cannot transit a stub area. In these cases, you will need to create a GRE tunnel to bridge the discontiguous area to an area 0 router. The task should hint at this by permitting you to create an additional subnet.

RIP - enabling unicast-only updates

Unlike OSPF, configuring the neighbor statement in RIP doesn't stop the transmission of broadcast/multicast (RIPv1 and RIPv2 respectively) update packets. Instead, it just sends an additional unicast update for the statically configured neighbors. In order to stop the transmission of broadcast/multicast updates and only send unicast updates you have to use the passive-interface command alone with the neighbor command. (IE)

Configuring FRTS disables fair queueing

WFQ needs to be enabled for RSVP. WFQ is the default queueing strategy on serial interfaces under 2.048 Mbps, but enabling FRTS on an interface disables fair queueing. (IE)

Passive Interface

The network statement does three things. First off the network statement advertises the networks configured on the interfaces that the network statement encompasses. These could be one or more networks. Secondly it enables the sending of updates or hellos, depending on the routing protocol used, outbound on the interface/interfaces. Lastly it allows updates or hellos to be received and processed inbound on the interface/interfaces.

The passive interface stops only one of these steps and that is the second step. It does not stop the advertisement of the network by the protocol or stop the receiving of inbound updates or hellos. Of course with any protocol that uses hellos that protocol will require a neighbor relationship to be formed before updates can be sent/received. (From B.D.)