ss lists and, 161 virtual circuits (see VCs) routing protocols and, 156-161 virtual command, 400 types of, 150 virtual interfaces (EtherChannels on IOS Turbo ACLs, 331 switches), 55, 62, 64 TX (transmitting) line, half-and full-duplex virtual interfaces, switched (see SVIs) links, 21 Virtual IP (VIP) address, 164 txload (transmit load), 441 virtual LANs (see VLANs) Type of Service (TOS) field, 422-425 virtual private networks (see VPNs) type-1 and type-2 external routes, OSPF, 138 Virtual Router Redundancy Protocol (VRRP), 163 virtual servers, 398 configuring in IOS SLB, 400 UDLD (Unidirectional Link Detection), 87 UDP, 419 configuring, 403 unicast storms, controlling, 233 residing in client VLAN, 401 Unidirectional Link Detection (UDLD), 87 showing status of, 409 unidirectional links, 86 vlan access-map command, 337 Unified Survivable Remote Site Telephony vlan command (IOS), 30 (SRST) modules, 222 name subcommand, 31 Unix systems, sending PIX firewall logs to vlan database command (IOS), 30 syslog server, 389 vlan filter command, 337 unshielded twisted pair (UTP) cables, 6 VLAN maps, 334 updates configuring, 336 classification as control packets in VLAN Trunking Protocol (see VTP) RIP, 135 VLANs (virtual LANs), 8, 24-32 ignoring on a specified interface in configuring, 27-32 RIP, 115 CatOS, 28 in RIPv2, 116 IOS, using global commands, 31 triggered and nontriggered, 112 IOS, using VLAN database, 29 upgrade command, 411 connecting, 24 upgrading routers and switches, 536-539 external routing between, 25 dangers of upgrading, 537 router on a stick configuration, 26 reasons to upgrade, 538 switches connected with a trunk, 25 UplinkFast, 81 corporate network design, 477 configuring only on access-layer creating RSPAN VLAN, 244 switches, 82 CSMs (Content Switching Modules), 401 username command, 345 layout, planning in network design, 466 assigning command to run automatically port assignments, showing in CatOS, 224 when user authenticates, 346 PVST (Per-VLAN Spanning Tree), 77 UTP (unshielded twisted pair) cables, 6 