s) three-tier architecture, 473 data port/DTE loopback, 281 Index Data Service Unit (DSU), 257 IP network, 484-505 (see also CSU/DSU) allocating IP address space, 491-494 data terminal equipment (DTE devices), allocating IP subnets, 494-498 communication with DCE CIDR, 490 devices, 307 IP subnetting made easy, 498-505 databases public VS. private IP space, 484-487 EIGRP, 120 VLSM, 487-489 OSPF, storage of routes in, 126 naming conventions for devices, 472 VLAN, 27 network designs, 473-483 configuring IOS with, 29 corporate networks, 473-477 DC power, 16 e-commerce web sites, 477-482 dCEF (distributed Cisco Express small networks, 482 Forwarding), 208 desirable (dynamic switchport mode), 38 D-channel (data channel), 259 desirable mode (PAgP), 60 DE (discard-eligible) frames, 303 CatOS EtherChannel, 61 debug auto qos command, 247 destination IP address debug frame-relay lmi command, 317 of GRE tunnel, 153 debug ip policy command, 179 load balancing with, 58 debug ppp authentication command, 348 destination MAC address, load balancing CHAP two-way authentication, 351 with, 56-60 debugging, using PIX logging output, 390 other options, 58 decrementing priority for tracked destination network, description of, 94 interfaces, 168 destination port, load balancing with, 58 default gateway, 92 differential service code point (see DSCP) listed in show ip route command Digital Access Cross-Connect System output, 96 (DACCS), 258 no default gateway configured or digital and analog, 254 learned, 96 digital signal (DS) hierarchy, 258 default queue, 458 Digital Signal 3 (see DS3) default route, 95, 100 disabled state (ports), 76 default-metric command, 133 disaster chains, 515 EIGRP, 136 discard-eligible (DE) frames, 303 delay metrics (EIGRP), 136 distance-vector routing protocols, 107 GRE tunnel interface, 156 EIGRP features, 117 demarc (demarcation point), 258 route poisoning, 111 demilitarized zone (see DMZ) distributed Cisco Express Forwarding deny clause clauses, 174 (dCEF), 208 designated bridge, 75 distribution level, netwo