871 connected to a 3550 Catalyst

Answered Question
Nov 8th, 2007

I am looking to create 2 VLAN's. VLAN 1 will be tunneling through a VPN to our corporate office. VLAN10 will be used for contractors to access the internet. I need help configuring the VLAN trunking, DHCP to supply to both VLAN's. I supplied my running configs minus some information. Thanks for your help.

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Correct Answer by Edison Ortiz about 9 years 3 weeks ago

on the router, enter this command:

sh int f0 switchport

You will see something like this

Administrative Trunking Encapsulation: dot1q

It won't show in the config because there is only one encapsulation option. If you had ISL as another option, it would be shown in the config.

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Edison Ortiz Thu, 11/08/2007 - 15:05

On the 3550 switchport connected to the router:

interface FastEthernetx/x

switchport trunk encap dot1q

switchport mode trunk

On the router port connected to the 3550:

interface FastEthernetx

switchport

switchport trunk encap dot1q

switchport mode trunk

On the router DHCP pool

ip dhcp excluded-address 10.10.24.254

ip dhcp pool sdm-pool2

network 10.10.24.0 255.255.255.0

domain-name [domain name for contractors]

default-router 10.10.24.254

dns-server [dns server for contractors]

netbios-name-server [ditto]

NAT for that segment

interface Vlan10

ip address 10.10.24.254 255.255.255.0

no ip redirects

no ip unreachables

no ip proxy-arp

ip nat inside

ip virtual-reassembly

ip route-cache flow

access-list 130 permit ip 10.10.24.0 0.0.0.255 any

obmis Fri, 11/09/2007 - 08:57

All entries went in with out a problem. Except the command on the router port connected to the 3550. In this case I am using interface fastethernet0. Switchport mode trunk works but am unable to do the switchport trunk encap dot1q. I can put it in but it does not seem to go into the running config. I saved the config and rebooted. Do I need a different IOS to support VLAN trunking? My reseller said no. Let me know. Thanks.

Current IOS c870-advsecurityk9-mz.124-11.XJ4.bin

Correct Answer
Edison Ortiz Fri, 11/09/2007 - 09:12

on the router, enter this command:

sh int f0 switchport

You will see something like this

Administrative Trunking Encapsulation: dot1q

It won't show in the config because there is only one encapsulation option. If you had ISL as another option, it would be shown in the config.

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