Connecting a 3800 to a 4507, a matter of how to set the IP....

[Emmanuel Farrar]

  I am expanding on a lab for my company and I have a a question due to me being unfamiliar with thee 4507R-E. I understand as a L3 device that I can't set static IPs to the interfaces so there are established vlans in place. Until now I have had only another 4507R-E switch and a 2960 switch in this lab, but now I am tasked to add a 3800 rtr to the lab and I am going through some issues. While CDP is fine and EIGRP is set across the 4507R-Es and created on the 3800 I am unable to ping the router. I am using the following configs.....

Config on 3800 router

interface GigabitEthernet0/0/0

description !!!Port connected to port 4/3 on CAT_4507RE_Left!!!

ip address 10.200.1.25 255.255.255.0

negotiation auto

Config on 4507

interface GigabitEthernet4/3

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 2

switchport mode trunk

VLAN config

interface Vlan2

ip address 10.200.1.20 255.255.255.0

Both lines are up and I am lost, lol.

Any help and advice???

[cadet alain · Accepted solution]

Hi,

try this:

on 3800 router

int g0/0/0

no ip add

int g0/0/0.2

encap dot1q 2

ip add 10.200.1.25 255.255.255.0

Regards.

Alain

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[Emmanuel Farrar]

Alain,

Thank you this worked great. Do you mind explaining what just happened here with your suggestion. I honestly forgot about sub interfaces, so any links to re-education me would be awesome.

Once again thank you!!!

[cadet alain]

Hi,

to support dot1q you need subinterfaces on the routeur so this was one way of achieving this but you could also have changed your switch port to mode access and  give it a port vlan id of 2, leaving the main interface on the router with the ip address.

Regards.

Alain

Don't forget to rate helpful posts.

[glen.grant]

  Also I don't know who told you about not having static ip addresses on a 4507 interface but that is an incorrect statement , it's like any other layer 3 switch you can either use SVI's and vlans or you can make the port a routed port with an address on it .  As Cadet indicated your original issue was you had the link on the 4507 setup as a trunk  and the router side was non trunked so it couldn't work .  Cadet had you set up a trunk using subinterfaces on the 3800 thus fixing your issue.