Dynamic Network Topology Mapper
.calc-header {
margin-bottom: 30px;
padding: 25px;
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
border-radius: 12px;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
color: white;
}
.calc-header h2 {
margin-top: 0;
color: white;
font-size: 28px;
margin-bottom: 10px;
}
.calc-header p {
margin: 10px 0 20px 0;
opacity: 0.95;
font-size: 15px;
line-height: 1.6;
}
.vendor-ref-section {
background: white;
border-radius: 8px;
padding: 20px;
margin-bottom: 20px;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.vendor-ref-section h3 {
margin-top: 0;
color: #667eea;
font-size: 18px;
margin-bottom: 15px;
}
.vendor-ref-layout {
display: grid;
grid-template-columns: 250px 1fr;
gap: 20px;
margin-top: 15px;
}
.vendor-tabs {
display: flex;
flex-direction: column;
gap: 5px;
}
.vendor-tab {
padding: 12px 16px;
background: #f5f5f5;
border: 2px solid transparent;
border-radius: 6px;
cursor: pointer;
font-size: 14px;
font-weight: 600;
color: #666;
text-align: left;
transition: all 0.2s ease;
}
.vendor-tab:hover {
background: rgba(102, 126, 234, 0.1);
color: #667eea;
}
.vendor-tab.active {
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
color: white;
border-color: #667eea;
}
.vendor-commands {
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 6px;
padding: 0;
position: relative;
}
.vendor-commands-header {
display: flex;
justify-content: space-between;
align-items: center;
padding: 12px 16px;
background: #667eea;
color: white;
border-radius: 6px 6px 0 0;
font-weight: bold;
font-size: 14px;
}
.vendor-commands pre {
margin: 0;
padding: 16px;
font-family: 'Courier New', monospace;
font-size: 13px;
color: #333;
background: white;
overflow-x: auto;
border-radius: 0 0 6px 6px;
}
.copy-btn {
padding: 6px 12px;
background: rgba(255, 255, 255, 0.2);
color: white;
border: 1px solid rgba(255, 255, 255, 0.3);
border-radius: 4px;
cursor: pointer;
font-size: 12px;
font-weight: bold;
transition: all 0.2s ease;
}
.copy-btn:hover {
background: rgba(255, 255, 255, 0.3);
}
.input-section {
background: white;
border-radius: 8px;
padding: 20px;
margin-bottom: 20px;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.input-section h3 {
margin-top: 0;
color: #667eea;
font-size: 18px;
margin-bottom: 15px;
}
.cli-textarea {
width: 100%;
min-height: 200px;
padding: 14px;
font-family: 'Courier New', monospace;
font-size: 13px;
border: 2px solid #e0e0e0;
border-radius: 6px;
resize: vertical;
transition: border-color 0.3s ease;
box-sizing: border-box;
}
.cli-textarea:focus {
outline: none;
border-color: #667eea;
box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}
.button-row {
display: flex;
gap: 10px;
margin-top: 15px;
flex-wrap: wrap;
}
.btn-primary {
padding: 12px 24px;
font-size: 14px;
background: #4CAF50;
color: white;
border: none;
border-radius: 6px;
cursor: pointer;
font-weight: bold;
transition: all 0.2s ease;
}
.btn-primary:hover {
background: #45a049;
transform: translateY(-1px);
}
.btn-secondary {
padding: 12px 24px;
font-size: 14px;
background: #667eea;
color: white;
border: none;
border-radius: 6px;
cursor: pointer;
font-weight: bold;
transition: all 0.2s ease;
}
.btn-secondary:hover {
background: #5568d3;
transform: translateY(-1px);
}
.btn-danger {
padding: 12px 24px;
font-size: 14px;
background: #f44336;
color: white;
border: none;
border-radius: 6px;
cursor: pointer;
font-weight: bold;
transition: all 0.2s ease;
}
.btn-danger:hover {
background: #d32f2f;
transform: translateY(-1px);
}
.device-chips {
display: flex;
flex-wrap: wrap;
gap: 10px;
margin-top: 15px;
min-height: 40px;
}
.device-chip {
display: inline-flex;
align-items: center;
gap: 8px;
padding: 8px 14px;
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
color: white;
border-radius: 20px;
font-size: 13px;
font-weight: 500;
box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}
.device-chip-label {
display: flex;
flex-direction: column;
}
.device-chip-hostname {
font-weight: bold;
}
.device-chip-info {
font-size: 11px;
opacity: 0.9;
}
.device-chip-remove {
background: rgba(255,255,255,0.2);
border: none;
color: white;
width: 20px;
height: 20px;
border-radius: 50%;
cursor: pointer;
font-size: 14px;
display: flex;
align-items: center;
justify-content: center;
transition: background 0.2s ease;
}
.device-chip-remove:hover {
background: rgba(255,255,255,0.4);
}
.view-tabs {
display: flex;
gap: 5px;
margin-bottom: 15px;
border-bottom: 2px solid #e0e0e0;
}
.view-tab {
padding: 12px 24px;
background: transparent;
border: none;
cursor: pointer;
font-size: 14px;
font-weight: 600;
color: #666;
border-bottom: 3px solid transparent;
transition: all 0.2s ease;
}
.view-tab:hover {
color: #667eea;
background: rgba(102, 126, 234, 0.05);
}
.view-tab.active {
color: #667eea;
border-bottom-color: #667eea;
}
.topology-canvas {
background: white;
border: 1px solid #e0e0e0;
border-radius: 8px;
height: 700px;
position: relative;
margin-bottom: 20px;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.empty-state {
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
height: 100%;
color: #999;
font-size: 16px;
}
.empty-state-icon {
font-size: 48px;
margin-bottom: 15px;
opacity: 0.5;
}
.details-panel {
background: white;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 20px;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
display: none;
}
.details-panel.visible {
display: block;
}
.details-header {
font-size: 18px;
font-weight: bold;
color: #667eea;
margin-bottom: 15px;
padding-bottom: 10px;
border-bottom: 2px solid #e0e0e0;
}
.details-grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
}
.details-item {
display: flex;
flex-direction: column;
}
.details-label {
font-size: 11px;
color: #666;
text-transform: uppercase;
letter-spacing: 0.5px;
margin-bottom: 5px;
}
.details-value {
font-size: 16px;
font-weight: bold;
color: #333;
}
.details-list {
margin-top: 15px;
}
.details-list h4 {
font-size: 14px;
color: #667eea;
margin-bottom: 10px;
}
.details-list-item {
padding: 8px 12px;
background: #f5f5f5;
border-radius: 4px;
margin-bottom: 6px;
font-size: 13px;
font-family: 'Courier New', monospace;
}
.notification {
position: fixed;
top: 20px;
right: 20px;
padding: 15px 20px;
border-radius: 6px;
box-shadow: 0 4px 12px rgba(0,0,0,0.2);
font-size: 14px;
z-index: 10000;
min-width: 300px;
animation: slideIn 0.3s ease;
}
@keyframes slideIn {
from {
transform: translateX(400px);
opacity: 0;
}
to {
transform: translateX(0);
opacity: 1;
}
}
.notification.success {
background: #4CAF50;
color: white;
}
.notification.error {
background: #f44336;
color: white;
}
.notification.warning {
background: #ff9800;
color: white;
}
.stats-bar {
display: flex;
gap: 20px;
padding: 15px 20px;
background: linear-gradient(135deg, rgba(102, 126, 234, 0.1) 0%, rgba(118, 75, 162, 0.1) 100%);
border-radius: 8px;
margin-bottom: 20px;
}
.stat-item {
display: flex;
flex-direction: column;
}
.stat-label {
font-size: 11px;
color: #666;
text-transform: uppercase;
letter-spacing: 0.5px;
}
.stat-value {
font-size: 24px;
font-weight: bold;
color: #667eea;
}
.legend {
display: flex;
flex-wrap: wrap;
gap: 15px;
padding: 15px;
background: white;
border-radius: 6px;
margin-top: 15px;
border: 1px solid #e0e0e0;
}
.legend-item {
display: flex;
align-items: center;
gap: 8px;
font-size: 13px;
}
.legend-color {
width: 20px;
height: 20px;
border-radius: 4px;
border: 1px solid rgba(0,0,0,0.1);
}
.search-filter-bar {
display: flex;
gap: 10px;
padding: 15px;
background: white;
border-radius: 6px;
margin-bottom: 15px;
border: 1px solid #e0e0e0;
align-items: center;
flex-wrap: wrap;
}
.search-input {
flex: 1;
min-width: 200px;
padding: 10px 14px;
border: 2px solid #e0e0e0;
border-radius: 6px;
font-size: 14px;
transition: border-color 0.3s ease;
}
.search-input:focus {
outline: none;
border-color: #667eea;
}
.filter-select {
padding: 10px 14px;
border: 2px solid #e0e0e0;
border-radius: 6px;
font-size: 14px;
cursor: pointer;
background: white;
}
.topology-storage-section {
display: flex;
gap: 10px;
flex-wrap: wrap;
}
.saved-topologies {
margin-top: 15px;
padding: 15px;
background: #f9f9f9;
border-radius: 6px;
border: 1px solid #e0e0e0;
}
.saved-topology-item {
display: flex;
justify-content: space-between;
align-items: center;
padding: 10px;
background: white;
border-radius: 4px;
margin-bottom: 8px;
border: 1px solid #e0e0e0;
}
.saved-topology-info {
flex: 1;
}
.saved-topology-name {
font-weight: bold;
color: #333;
font-size: 14px;
}
.saved-topology-meta {
font-size: 12px;
color: #666;
margin-top: 4px;
}
.saved-topology-actions {
display: flex;
gap: 8px;
}
.path-selection-bar {
padding: 15px;
background: linear-gradient(135deg, rgba(76, 175, 80, 0.1) 0%, rgba(76, 175, 80, 0.05) 100%);
border-radius: 6px;
margin-bottom: 15px;
border: 2px solid #4CAF50;
}
.path-selection-bar h4 {
margin: 0 0 10px 0;
color: #4CAF50;
font-size: 14px;
}
.path-info {
display: flex;
gap: 20px;
align-items: center;
flex-wrap: wrap;
}
.path-node {
padding: 8px 14px;
background: white;
border-radius: 6px;
font-weight: bold;
color: #333;
border: 2px solid #4CAF50;
}
.path-details {
flex: 1;
font-size: 13px;
color: #333;
}
@media (max-width: 768px) {
.topology-container {
padding: 10px;
}
.vendor-ref-layout {
grid-template-columns: 1fr;
}
.button-row {
flex-direction: column;
}
.btn-primary,
.btn-secondary,
.btn-danger {
width: 100%;
}
.stats-bar {
flex-direction: column;
gap: 10px;
}
.topology-canvas {
height: 500px;
}
.search-filter-bar {
flex-direction: column;
align-items: stretch;
}
.search-input {
min-width: 100%;
}
.sample-topology-selector {
flex-direction: column;
}
}
.sample-topology-selector {
display: flex;
gap: 10px;
align-items: center;
margin-top: 10px;
}
.sample-topology-selector select {
flex: 1;
padding: 10px 14px;
border: 2px solid #e0e0e0;
border-radius: 6px;
font-size: 14px;
background: white;
cursor: pointer;
}
.sample-topology-selector select:focus {
border-color: #667eea;
outline: none;
}
.difficulty-badge {
display: inline-block;
padding: 2px 8px;
border-radius: 12px;
font-size: 11px;
font-weight: 600;
text-transform: uppercase;
letter-spacing: 0.5px;
}
.difficulty-badge.beginner { background: #e8f5e9; color: #2e7d32; }
.difficulty-badge.intermediate { background: #fff3e0; color: #e65100; }
.difficulty-badge.advanced { background: #fce4ec; color: #c62828; }
.training-note {
margin: 15px 0;
padding: 15px 20px;
background: #e3f2fd;
border-left: 4px solid #1976D2;
border-radius: 0 6px 6px 0;
font-size: 14px;
line-height: 1.6;
color: #1565C0;
}
.training-note strong {
display: block;
margin-bottom: 5px;
color: #0D47A1;
}
.vrf-badge {
display: inline-block;
padding: 1px 6px;
border-radius: 8px;
font-size: 10px;
font-weight: 600;
margin-left: 4px;
color: white;
}
.route-leak-indicator {
color: #e74c3c;
font-weight: 600;
font-size: 12px;
}
.vrf-detail-section {
margin-top: 10px;
padding: 10px;
background: #f5f5f5;
border-radius: 6px;
border-left: 3px solid #667eea;
}
.vrf-detail-section h5 {
margin: 0 0 6px 0;
font-size: 13px;
color: #333;
}
.vrf-detail-item {
font-size: 12px;
color: #555;
margin-bottom: 3px;
}
.vrf-legend {
display: flex;
flex-wrap: wrap;
gap: 8px;
margin-top: 10px;
padding: 10px;
background: #f9f9f9;
border-radius: 6px;
}
.vrf-legend-item {
display: flex;
align-items: center;
gap: 4px;
font-size: 11px;
}
.vrf-legend-color {
width: 12px;
height: 12px;
border-radius: 3px;
}
/* =========================================================
WIZARD MODAL — Phase 3
========================================================= */
.wizard-overlay {
position: fixed;
inset: 0;
background: rgba(0, 0, 0, 0.55);
z-index: 9000;
display: flex;
align-items: center;
justify-content: center;
padding: 20px;
animation: fadeOverlay 0.2s ease;
}
@keyframes fadeOverlay {
from { opacity: 0; }
to { opacity: 1; }
}
.wizard-modal {
background: white;
border-radius: 12px;
box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
width: 100%;
max-width: 680px;
max-height: 90vh;
overflow-y: auto;
display: flex;
flex-direction: column;
animation: slideUp 0.25s ease;
}
@keyframes slideUp {
from { transform: translateY(30px); opacity: 0; }
to { transform: translateY(0); opacity: 1; }
}
.wizard-header {
display: flex;
align-items: center;
justify-content: space-between;
padding: 20px 24px 16px;
border-bottom: 2px solid #f0f0f0;
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
border-radius: 12px 12px 0 0;
color: white;
}
.wizard-header h3 {
margin: 0;
font-size: 18px;
color: white;
}
.wizard-close-btn {
background: rgba(255,255,255,0.2);
border: none;
color: white;
width: 32px;
height: 32px;
border-radius: 50%;
cursor: pointer;
font-size: 18px;
display: flex;
align-items: center;
justify-content: center;
transition: background 0.2s;
flex-shrink: 0;
}
.wizard-close-btn:hover {
background: rgba(255,255,255,0.35);
}
.wizard-progress-bar {
height: 4px;
background: #e0e0e0;
position: relative;
overflow: hidden;
}
.wizard-progress-fill {
height: 100%;
background: linear-gradient(90deg, #667eea, #764ba2);
transition: width 0.35s ease;
}
.wizard-body {
padding: 24px;
flex: 1;
}
.wizard-step-label {
font-size: 12px;
font-weight: 600;
text-transform: uppercase;
letter-spacing: 0.6px;
color: #667eea;
margin-bottom: 6px;
}
.wizard-command-block {
display: inline-block;
padding: 8px 14px;
background: #1e1e2e;
color: #a6e3a1;
font-family: 'Courier New', monospace;
font-size: 14px;
border-radius: 6px;
margin: 10px 0 16px;
word-break: break-all;
}
.wizard-command-copy {
display: inline-block;
margin-left: 10px;
padding: 3px 10px;
background: transparent;
border: 1px solid #667eea;
color: #667eea;
border-radius: 4px;
font-size: 11px;
cursor: pointer;
font-weight: 600;
transition: all 0.15s;
vertical-align: middle;
}
.wizard-command-copy:hover {
background: #667eea;
color: white;
}
.wizard-textarea {
width: 100%;
min-height: 220px;
padding: 14px;
font-family: 'Courier New', monospace;
font-size: 12px;
border: 2px solid #e0e0e0;
border-radius: 6px;
resize: vertical;
box-sizing: border-box;
transition: border-color 0.25s;
line-height: 1.5;
}
.wizard-textarea:focus {
outline: none;
border-color: #667eea;
box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}
.wizard-textarea.invalid {
border-color: #f44336;
}
.wizard-inline-error {
color: #f44336;
font-size: 13px;
margin-top: 6px;
display: none;
}
.wizard-validation-warning {
background: #fff8e1;
border: 1px solid #f9a825;
border-radius: 6px;
padding: 12px 16px;
font-size: 13px;
color: #5d4037;
margin-top: 10px;
display: none;
}
.wizard-validation-warning strong {
color: #e65100;
display: block;
margin-bottom: 6px;
}
.wizard-validation-actions {
display: flex;
gap: 10px;
margin-top: 8px;
}
.wizard-footer {
display: flex;
align-items: center;
justify-content: space-between;
padding: 16px 24px;
border-top: 1px solid #f0f0f0;
gap: 10px;
flex-wrap: wrap;
}
.wizard-back-link {
background: none;
border: none;
color: #667eea;
cursor: pointer;
font-size: 14px;
padding: 0;
text-decoration: underline;
text-underline-offset: 2px;
}
.wizard-back-link:hover {
color: #5568d3;
}
.wizard-btn-row {
display: flex;
gap: 10px;
}
.btn-wizard-skip {
padding: 10px 20px;
font-size: 14px;
background: transparent;
color: #888;
border: 2px solid #e0e0e0;
border-radius: 6px;
cursor: pointer;
font-weight: 600;
transition: all 0.2s;
}
.btn-wizard-skip:hover {
border-color: #999;
color: #555;
}
.btn-wizard-next {
padding: 10px 24px;
font-size: 14px;
background: #4CAF50;
color: white;
border: none;
border-radius: 6px;
cursor: pointer;
font-weight: bold;
transition: all 0.2s;
}
.btn-wizard-next:hover {
background: #43a047;
transform: translateY(-1px);
}
.btn-wizard-finalize {
padding: 10px 24px;
font-size: 14px;
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
color: white;
border: none;
border-radius: 6px;
cursor: pointer;
font-weight: bold;
transition: all 0.2s;
}
.btn-wizard-finalize:hover {
opacity: 0.9;
transform: translateY(-1px);
}
/* Step 0 — Identity form */
.wizard-identity-form {
display: flex;
flex-direction: column;
gap: 16px;
}
.wizard-field-group {
display: flex;
flex-direction: column;
gap: 6px;
}
.wizard-field-group label {
font-size: 13px;
font-weight: 600;
color: #444;
}
.wizard-text-input,
.wizard-select {
width: 100%;
padding: 12px 14px;
border: 2px solid #e0e0e0;
border-radius: 6px;
font-size: 14px;
box-sizing: border-box;
transition: border-color 0.25s;
background: white;
}
.wizard-text-input:focus,
.wizard-select:focus {
outline: none;
border-color: #667eea;
box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}
/* Summary step */
.wizard-summary-list {
list-style: none;
padding: 0;
margin: 16px 0;
}
.wizard-summary-list li {
display: flex;
align-items: center;
gap: 10px;
padding: 9px 12px;
border-radius: 6px;
font-size: 14px;
margin-bottom: 4px;
}
.wizard-summary-list li:nth-child(odd) {
background: #f9f9f9;
}
.wizard-summary-icon {
width: 22px;
height: 22px;
border-radius: 50%;
display: flex;
align-items: center;
justify-content: center;
font-size: 12px;
font-weight: bold;
flex-shrink: 0;
}
.wizard-summary-icon.submitted {
background: #e8f5e9;
color: #2e7d32;
}
.wizard-summary-icon.skipped {
background: #f5f5f5;
color: #999;
}
.wizard-summary-cmd {
flex: 1;
}
.wizard-summary-status {
font-size: 12px;
font-weight: 600;
color: #999;
}
.wizard-summary-status.submitted {
color: #4CAF50;
}
.wizard-summary-identity {
padding: 14px 16px;
background: linear-gradient(135deg, rgba(102, 126, 234, 0.08) 0%, rgba(118, 75, 162, 0.08) 100%);
border-radius: 8px;
border-left: 4px solid #667eea;
font-size: 14px;
margin-bottom: 6px;
}
.wizard-summary-identity strong {
font-size: 16px;
display: block;
margin-bottom: 4px;
color: #333;
}
.wizard-summary-vendor-badge {
display: inline-block;
padding: 2px 10px;
border-radius: 20px;
font-size: 11px;
font-weight: 700;
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
color: white;
text-transform: uppercase;
letter-spacing: 0.5px;
}
/* Quick-add (legacy) section toggle */
.quick-add-toggle {
display: flex;
align-items: center;
gap: 8px;
padding: 10px 0 0;
cursor: pointer;
color: #667eea;
font-size: 13px;
font-weight: 600;
border: none;
background: none;
text-decoration: none;
user-select: none;
}
.quick-add-toggle:hover {
color: #5568d3;
}
.quick-add-caret {
display: inline-block;
transition: transform 0.2s;
font-style: normal;
}
.quick-add-caret.open {
transform: rotate(90deg);
}
.quick-add-body {
overflow: hidden;
max-height: 0;
transition: max-height 0.3s ease, padding 0.3s ease;
}
.quick-add-body.open {
max-height: 600px;
}
/* Devices collected list */
.wizard-collected-list {
margin-top: 16px;
}
.wizard-collected-list h4 {
font-size: 13px;
font-weight: 700;
color: #667eea;
margin: 0 0 10px;
text-transform: uppercase;
letter-spacing: 0.5px;
}
.wizard-collected-empty {
color: #999;
font-size: 13px;
font-style: italic;
}
@media (max-width: 768px) {
.wizard-modal {
max-height: 95vh;
}
.wizard-textarea {
min-height: 200px;
}
.wizard-footer {
flex-direction: column;
align-items: stretch;
}
.wizard-btn-row {
width: 100%;
justify-content: flex-end;
}
}
======================================================
ตัวช่วยสร้าง MODAL (ซ่อนไว้โดยค่าเริ่มต้น)
======================================================
เพิ่มด่วนแบบเดิม (ยุบ)
ตัวทำแผนที่โทโพโลยีเครือข่ายแบบไดนามิก
เครื่องมือแสดงภาพเครือข่ายแบบ Zero-trust ที่ประมวลผลเอาต์พุตของ CLI ฝั่งไคลเอ็นต์ทั้งหมด วางเอาต์พุตจากอุปกรณ์หลายเครื่องเพื่อสร้างไดอะแกรมโทโพโลยีเชิงโต้ตอบโดยอัตโนมัติ รองรับ Cisco IOS/NX-OS, Aruba AOS-CX, Juniper JunOS, VyOS, Palo Alto, Fortigate และ SONiC
รับประกันความเป็นส่วนตัว:การประมวลผลทั้งหมดเกิดขึ้นในเบราว์เซอร์ของคุณ ไม่มีการส่งข้อมูลไปยังเซิร์ฟเวอร์ใด ๆ
การอ้างอิงคำสั่งของผู้ขาย
เลือกผู้จำหน่ายอุปกรณ์ของคุณเพื่อดูคำสั่ง CLI ที่แนะนำสำหรับการค้นหาเครือข่าย:
คำสั่ง Cisco IOS/IOS-XE
show lldp neighbors show lldp neighbors detail show mac address-table show ip ospf neighbor show ip bgp summary show cdp neighbors detail show interfaces status show vlan brief
ขั้นตอนที่ 1: เพิ่มอุปกรณ์
รายการตัวช่วยสร้างเปิดตัว + อุปกรณ์ที่รวบรวมยังไม่มีอุปกรณ์เพิ่ม — ใช้วิซาร์ดหรือเพิ่มด่วนด้านล่าง