Cisco CCNA Study Guide - Router Alley

More documents

Recommendations

Info

CCNA Study Guide v2.62 – Aaron Balchunas 248 Native VLANs A native VLAN can also be configured on trunk ports: Switch(config)# interface fa0/24 Switch(config-if)# switchport mode trunk Switch(config-if)# switchport trunk native vlan 42 Frames from the native VLAN are not tagged when sent out trunk ports. A trunking interface can only be assigned one native VLAN. Only 802.1Q supports native VLANs, whereas ISL does not. (More accurately, ISL will tag frames from all VLANs, even if a VLAN is configured as native). The native VLAN should be configured identically on both sides of the 802.1Q trunk). Native VLANs are often configured when plugging Cisco VoIP phones into a Catalyst Switch (beyond the scope of this section). Native VLANs are also useful if a trunk port fails. For example, if an end user connects a computer into a trunk port, the trunking status will fail and the interface will essentially become an access port. The user’s computer will then be transparently joined to the Native VLAN. Native VLANs provide another benefit. A trunk port will accept untagged frames and place them in the Native VLAN. Consider the following example: Assume that both 802.1Q switches have trunk links configured to the non- 802.1Q switch, and that the trunk ports are configured in Native VLAN 42. Not only will the 802.1Q switches be able to communicate with each other, the non-802.1Q switch will be placed in Native VLAN 42, and be able to communicate with any device in VLAN 42 on any switch. (Please note, that the author of this study guide finds the “benefit” of the above example of Native VLANs to be……dubious at best, and confusing as hell at worst). By default on all trunking interfaces, the Native VLAN is VLAN 1. * * * All original material copyright © 2013 by Aaron Balchunas (aaron@routeralley.com), unless otherwise noted. All other material copyright © of their respective owners. This material may be copied and used freely, but may not be altered or sold without the expressed written consent of the owner of the above copyright. Updated material may be found at http://www.routeralley.com.
CCNA Study Guide v2.62 – Aaron Balchunas 249 Dynamic Trunking Protocol (DTP) Configuration Not only can the frame tagging protocol of a trunk port be auto-negotiated, but whether a port actually becomes a trunk can be negotiated dynamically as well using the Dynamic Trunking Protocol (DTP). To manually set a port to be a trunk: Switch(config)# interface fa0/24 Switch(config-if)# switchport mode trunk To allow a port to dynamically decide whether to become a trunk, there are two options: Switch(config)# interface fa0/24 Switch(config-if)# switchport mode dynamic desirable Switch(config)# interface fa0/24 Switch(config-if)# switchport mode dynamic auto If a switchport is set to dynamic desirable (the default dynamic setting), the interface will actively attempt to form a trunk with the remote switch. If a switchport is set to dynamic auto, the interface will passively wait for the remote switch to initiate the trunk. This results in the following: • If both ports are manually set to trunk - a trunk will form. • If one port is set to dynamic desirable, and the other is set to manual trunk, dynamic desirable, or dynamic auto - a trunk will form. • If one port is set to dynamic auto, and the other port is set to manual trunk or dynamic desirable - a trunk will form. • If both ports are set to dynamic auto, the link will never become a trunk, as both ports are waiting for the other to initialize the trunk. Trunk ports send out DTP frames every 30 seconds to indicate their configured mode. In general, it is best to manually specific the trunk link, and disable DTP using the switchport nonegotiate command: Switch(config)# interface fa0/24 Switch(config-if)# switchport mode trunk Switch(config-if)# switchport nonegotiate * * * All original material copyright © 2013 by Aaron Balchunas (aaron@routeralley.com), unless otherwise noted. All other material copyright © of their respective owners. This material may be copied and used freely, but may not be altered or sold without the expressed written consent of the owner of the above copyright. Updated material may be found at http://www.routeralley.com.
Page 1 and 2:
CCNA Study Guide v2.62 - Aaron Balc
Page 3 and 4:
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199: CCNA Study Guide v2.62 - Aaron Balc
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304:
show all

Cisco CCNA Study Guide - Router Alley

Create successful ePaper yourself

Delete template?

Save as template?