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Using Internal VLAN ID as Extended VLAN ID on Cisco IOS

VLAN ID is 12 bit long value – in range from 0 to 4095. Numbers 0 and 4095 cannot be used. VLANs 1, 1002 – 1005 are default VLANs and cannot be changed or deleted by users. In the old times, only VLANs 2 – 1001 were allowed to be configured. Later on, extended range was introduced and now we can use also VLANs 1006 – 4094. This extended space is not saved into VLAN database.

There is one problem however. Something, what is called internal VLAN. Internal VLANs are allocated for every feature and physical port. More ports you have, more VLANs are used for internal usage. You don’t see them, when you type show vlan brief. If you want to use extended range, it is recommended to start with the highest VLAN number and decrement values by one for other VLANs.

When you want or need to use VLAN, which is assigned as internal VLAN, you may encounter an error message like this:

SW1(config)#vlan 100
VLAN id: 100 is an internal vlan id - cannot use it to create a VTP VLAN.

Solution

One way is to use another VLAN. To show all the internal VLANs, use:

show vlan internal usage

“To configure an extended VLAN with a number that is assigned to an internal VLAN, follow these steps:

Example

Example from one of the switches:

SW1#show vlan internal usage 

VLAN Usage
---- --------------------
100  TenGigabitEthernet5/5
1006 online diag vlan0   
1007 online diag vlan1   
1008 online diag vlan2   
1009 online diag vlan3   
1010 online diag vlan4   
1011 online diag vlan5   
1012 PM vlan process (trunk tagging)
1013 Control Plane Protection
1014 L3 multicast partial shortcuts for VPN 0
1015 Egress internal vlan
1016 Multicast VPN 0 QOS vlan
1017 IPv6 Multicast Egress multicast
1018 GigabitEthernet4/1
1019 TenGigabitEthernet1/4
1020 TenGigabitEthernet1/5
1021 TenGigabitEthernet1/1
1022 TenGigabitEthernet1/2
1023 TenGigabitEthernet1/3
1024 GigabitEthernet2/4
1025 TenGigabitEthernet5/5
1027 GigabitEthernet3/32
1028 GigabitEthernet2/2
1029 GigabitEthernet2/3
1030 TenGigabitEthernet1/6
1031 TenGigabitEthernet1/7
1032 GigabitEthernet2/6
1033 GigabitEthernet2/7
1034 GigabitEthernet4/2
1035 GigabitEthernet4/3
1036 GigabitEthernet4/4
1037 GigabitEthernet2/11
1038 GigabitEthernet2/12
1039 GigabitEthernet2/13
1040 GigabitEthernet2/14
1045 GigabitEthernet2/19
1046 GigabitEthernet2/20
1047 GigabitEthernet2/21
1048 GigabitEthernet2/22
1050 GigabitEthernet2/24
1052 GigabitEthernet2/26
1054 GigabitEthernet2/28
1055 GigabitEthernet2/29
1057 GigabitEthernet2/31
1058 GigabitEthernet2/32
1059 GigabitEthernet2/33

VLAN Usage
---- --------------------

1060 GigabitEthernet2/34
1061 GigabitEthernet2/35
1062 GigabitEthernet2/36
1063 GigabitEthernet2/37
1064 GigabitEthernet2/38
1065 GigabitEthernet2/39
1066 GigabitEthernet2/40
1067 GigabitEthernet2/41
1069 GigabitEthernet2/43
1070 GigabitEthernet2/44
1071 GigabitEthernet2/45
1072 GigabitEthernet2/46
1073 GigabitEthernet2/47
1074 GigabitEthernet2/48
1075 GigabitEthernet4/5
1076 GigabitEthernet4/6
1077 GigabitEthernet4/7
1078 GigabitEthernet4/8
1079 GigabitEthernet3/5
1080 GigabitEthernet3/6
1081 GigabitEthernet3/7
1082 GigabitEthernet3/8
1083 GigabitEthernet3/9
1084 GigabitEthernet3/10
1085 GigabitEthernet3/11
1086 GigabitEthernet3/12
1087 GigabitEthernet3/13
1088 GigabitEthernet3/14
1093 GigabitEthernet3/19
1095 GigabitEthernet3/21
1096 GigabitEthernet3/22
1097 GigabitEthernet3/23
1098 GigabitEthernet3/24
1099 GigabitEthernet3/25
1101 GigabitEthernet3/27
1102 GigabitEthernet3/28
1104 GigabitEthernet3/30
1107 GigabitEthernet3/33
1108 GigabitEthernet3/34
1109 GigabitEthernet3/35
1110 GigabitEthernet3/36
1111 GigabitEthernet3/37
1112 GigabitEthernet3/38
1113 GigabitEthernet3/39
1114 GigabitEthernet3/40
1115 GigabitEthernet3/41
1116 GigabitEthernet3/42
1117 GigabitEthernet3/43
1118 GigabitEthernet3/44
<output omitted>

You can see that VLANs 1105 and 1106 are missing. They were allocated, but I have used them. One more interesting thing, also VLAN 100 is internal, so this does affect not only extended range.

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