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New Member

subinterface error

when I configure a subinterface of the interface fastethernet 0/1 in router 2621 ,it is error ,as follow:

"Router(config-subif)#ip address

Configuring IP routing on a LAN subinterface is only allowed if that

subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q, or ISL vLAN."

router 2621 ios :

"IOS (tm) C2600 Software (C2600-I-M), Version 12.2(8)T5, RELEASE SOFTWARE (fc1)

ROM: System Bootstrap, Version 12.2(7r) [cmong 7r], RELEASE SOFTWARE (fc1)

cisco 2621XM (MPC860P) processor (revision 0x100) with 125952K/5120K bytes of memory."

how to do ?


Re: subinterface error

Are you configuring sub interfaces for inter vlan routing ?

Then you need to configure encapsulation for the sub interfaces as follows

int fa0/0.10

description vlan 10

encapsulation isl 10 (you can use dot1q instead of isl also)

ip add <> <>

int fa0/0.20

description vlan 20

encapsulation isl 20

ip add <> <>

New Member

Re: subinterface error

yes,I configure subinterfaces .and I do all as you ,but there is not the "encapsulation "command

as follows:


2621(config)#interface fas 0/1.1


Interface configuration commands:

arp Set arp type (arpa, probe, snap) or timeout

backup Modify backup parameters

bandwidth Set bandwidth informational parameter

bridge-group Transparent bridging interface parameters

cdp CDP interface subcommands

default Set a command to its defaults

delay Specify interface throughput delay

description Interface specific description

exit Exit from interface configuration mode

ip Interface Internet Protocol config commands

llc2 LLC2 Interface Subcommands

mtu Set the interface Maximum Transmission Unit (MTU)

netbios Use a defined NETBIOS access list or enable name-caching

no Negate a command or set its defaults

ntp Configure NTP

rate-limit Rate Limit

service-policy Configure QoS Service Policy

shutdown Shutdown the selected interface

snapshot Configure snapshot support on the interface

standby HSRP interface configuration commands

timeout Define timeout values for this interface


as so that ,then what to do ?

Re: subinterface error

Your IOS is 12.2(8)T5. This IOS does support ISL and 802.1q trunking. But that depends on the feature set used. For this feature to be available on the IOS, a minimum of IP Plus feature set should be used. I dont know if you are using IP only feature set. Please paste the name of the IOS image file you are using. It would look like this....(this is a sample c2600-is-mz.12.2-8.T5). From that we can determine, the feature set of the IOS.

Hope that helps!

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