signs, 367-368 failures, 513-520 best practices, 361-363 disaster chains, 515 deny everything, permit what you human error, 513 need, 362 multiple component failure, 514 everything not yours belongs no failover testing, 516 outside, 363 troubleshooting, 516-520 monitor the logs, 362 assuming nothing; proving simple is good, 362 everything, 518 configuring to allow GRE, 161 checking physical layer first, 518 DMZ, 363-367 don't look for zebras, 519 connectivity to a third party, 365 escalating to someone else, 520 firewall configuration, 364 finding out what changed, 517 multiple DMZ example, 366 isolating the problem, 519 rules allowing services as needed, 365 Janitor Principle, 520 (see also PIX firewalls) logging your actions, 517 five-minute offered rate, 451 performing a physical audit, 519 fixed-configuration switches, 14 remaining calm, 517 benefits of, 14 in a team environment, 520 fixup command, 376 far-end alarm and control (FEAC) codes, 291 fixups (PIX firewall), 375 far-end block errors (FEBEs), 290, 294 default on Version 6.2, 376 far-end out-of-frame (FEOOF) signals, 290 SMTP fixup, 375 Fast EtherChannel (FEC) (see EtherChannel) viewing status of, 376 fast switching, 181, 185-187 flex links, 233 binary tree format for route cache FlexWAN modules, 222 information, 185 Foreign eXchange Service (FXS) configuring and managing switching modules, 222 paths, 192 Forward-Explicit Congestion Notification disadvantages of route cache, 186 (FECN), 308 fault tolerance, 401 forwarding state (ports), 76 replicating changes in primary CSM to forwarding table (CEF trie), 189 secondary, 408 FQDN (fully qualified domain name), 472 FCS (frame check sequence), ISL and frame check sequence (FCS), ISL and Ethernet, 35 Ethernet, 35 FDDI (Fiber Distributed Data Interface), 3 frame relay, 299-319 FDDI networks, support by OSPF, 125 bandwidth utilization graph for a FEAC (far-end alarm and control) codes, 291 link, 303 FEBE (far-end block errors), 290, 294 benefits of, 302 FEC (Fast EtherChannel) (see EtherChannel) configuring