Setting up Switch module on 2951

Patrick McHenry · ‎09-19-2012

Hi,

I'm trying to set up a 2951 with a 24 port switch module. I want the ports to act similiarly to the ports on an 881 router - where I assign the VLANs on the router and I set the VLANs to the switchport interfaces.

I would like to be able to create the VLANs on the router portion of the 2951 and then, enter the switch module and configure the Ports to the VLANs but, how do I logically connect router to the switch? Is it an internal logical interface - meaning how are the VLANs getting from the router to the switch?

Thanks, Pat.

Reza Sharifi · ‎09-19-2012

Hi Pat,

You need to configure the routers gi1/0 interface first using a console cable before you can access the switch module and configure it. This is the interface that connects the router to the switch

To configure an IP address and subnet mask for Gigabit Ethernet interface (gigabitethernet 1/0) on the router, use the following command:

Router(config)#interface gigabitethernet 1/0

Router(config-if)#ip address 10.1.1.111 255.255.255.252

•To open a session from the router to the Cisco enhanced EtherSwitch service module, use the following command:

Router#service-module gigabitethernet1/0 session

follow this link:

http://www.cisco.com/en/US/docs/routers/access/interfaces/software/feature/guide/eesm_sw.html#wp1942894

HTH

Patrick McHenry · ‎09-19-2012

Thanks Reza,

I've done this. I can get into the switch module doing it the same way you described. My problem is how do the router and switch communicate the VLANS? Is there an internal switch fabric between the two like the 881s?

For instance; on the 881s I configure the VLANs and VLAN interface IPs on the router then, I configure the switchports to a VLAN. I'm wondering where I should configure the VLANs and their ip addresses - on the router or switch and how do the router and switch module exchange data between them?

Thanks, Pat.

Reza Sharifi · ‎09-19-2012

Pat,

If I remember correctly, it is the last port on the switch module. do a "sh ip int bri"

If you have a 24 port module, than it should be port 25 or 26.

HTH

Patrick McHenry · ‎09-19-2012

Thanks Reza.

What are these interfaces - are they the connection to the router? If so, do I configure them as trunks to use the VLANs that were configured on the router? And, what interface on the router connects to them, if any?

Thanks, Pat.

Reza Sharifi · ‎09-19-2012

Pat,

If the interface is in up and up mode, do a "sh cdp nei" it will tell you what port on the router it is connected to. It may be gi2/0 but not sure

HTH

Patrick McHenry · ‎09-19-2012

Switch#sh cdp neigh
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID        Local Intrfce     Holdtme    Capability Platform Port ID
mchenry.pcc.int Gig 0/26          169              R S   CISCO2951 Gig 2/0
mchenry.pcc.int Gig 0/25          142              R S   CISCO2951 Gig 2/1
Switch#

I did a ctrl shift 6 then x

Then I go into the router...........

mchenry#sh ip int br

Interface IP-Address OK? Method Status Protocol

Embedded-Service-Engine0/0 unassigned YES NVRAM administratively down down

GigabitEthernet0/0 unassigned YES NVRAM down down

GigabitEthernet0/1 172.17.0.17 YES NVRAM down down

GigabitEthernet0/2 unassigned YES NVRAM administratively down down

GigabitEthernet2/0 1.1.1.1 YES manual up up

GigabitEthernet2/1 unassigned YES unset up up

NVI0 unassigned YES unset administratively down down

Tunnel0 172.20.68.12 YES NVRAM up down

Tunnel1 10.3.68.12 YES NVRAM up down

Vlan1 unassigned YES unset up up

mchenry#

So it appears that I'm connecting to the switch module through gig2/0 on the router for management but , this still doesn't answer the question I have for configuring. I want the connection between ther router and switch module to be layer 2. Should I make the g2/0 on ther router and the g0/26 on the switch trunk ports. Or is ther a more elegant way of doing this?

By the way what is the embedded-service-Engine0/0?

Thanks, Pat.

Reza Sharifi · ‎09-19-2012

Correct, you would need the trunk 0/25 on the switch side and 2/1 on the router side since they are neighbors. These are internal interfaces.

mchenry.pcc.int Gig 0/25 142 R S CISCO2951 Gig 2/1

HTH

Patrick McHenry · ‎09-19-2012

OK.

What about the g0/26 to g2/0 link? Should I just shut that?

It would seem weird to me to have one layer 3 connection and one trunk connection, wouldn't it? Or, is this the way it is done?

Thanks, Pat.

Reza Sharifi · ‎09-19-2012

Isn't gi2/0 (ip 1.1.1.1) the one you use to session to the switch? If yes, than you need to have this interface in up and up mode in order to get from the router to the switch.

By the way what is the embedded-service-Engine0/0?

http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/cimce/1.0/configuration/guide/CIMCe.html#wp1104930

HTH

Patrick McHenry · ‎09-19-2012

Reza,

I'm trying to understand this concept of the switch module inside a router and I'm not getting any closer.

The config will have 2 VLANs - 10 and 30 both sharing the same subnet and IP. 10 will be for data and 30 will be for voice.

So, should I create the VLANs on the switch then, configure a VLAN 10 interface and a VLAN 30 interface on the router? And create a trunk between the router and switch. g2/1 on the router and g0/25 on the switch?

Thanks, Pat.

Reza Sharifi · ‎09-19-2012

Pat,

First, usually you assign one vlan to one subnet and not 2 vlans to one subnet. It does work, but it is not common and also confusing. So, if you are planning 2 have 2 vlans, assign a subnet to each. Specially since one of your vlan (30) will be used for voice, it is always a good idea to keep the voice vlan/subnet separate from data.

Example:

192.168.10.0/24 vlan 10 data

192.168.30.0/24 vlan 30 voice

Now, let me explain the switch concept.

Think about the switch module as regular 3560 switch. As a matter of fact the switch module inside your router runs the same image that you load on a standalone 3560 switch. Now, you create 2 layer-2 vlans (10 and 30) on the switch module.

config t

vlan 10

name data vlan

config t

vlan 30

name voice vlan

now, you trunk interface gi0/25

On the router side you now add 2 sub-interfaces to gi2/1 (one for vlan 10 and one for vlan 30)

example:

config t

inter gi2/1.10

ip address 192.168.10.1 255.255.255.0

encap dot.1q 10

inter gi2/1.30

ip address

192.168.30.1 255.255.255.0

encap dot.1q 30

So, the route routes between vlan 10 and 30.

It this more clear now?

HTH

Reza

Patrick McHenry · ‎09-20-2012

Thanks for answering so late.

Yes that does clear things up a lot!!

I know the 2 VLANs on one subnet is a little confusing but, that is how we have been deploying the 881s to remote users so, I'm going to keep it standard for the small office-2951s.

This brings up some more questions:

I'm a little confused about the g2/1 and g2/0. Does Cisco give you 2 of these "logical" interfaces for the purpose of what I want to accomplish - provide a trunk between the router and switch module for passing VLANs or I gues you could keep it an access port for a flat network using one interface and also provide a layer three connection for management using the other?

Thanks, Pat.

Patrick McHenry · ‎09-20-2012

Thought I might include this to give you a better idea of what I am trying to accomplish.

This is the VLAN interface configs on the 881s:

interface Vlan10

description Corporate Access

ip address 172.16.0.209 255.255.255.248

no ip redirects

no ip unreachables

ip nat inside

ip inspect cvo-inspect in

ip virtual-reassembly

ip tcp adjust-mss 1360

no autostate

!

service-policy input mark_incoming_traffic

interface Vlan20

description Guest Access

ip address 192.168.68.1 255.255.255.0

ip nat inside

ip inspect cvo-inspect in

ip virtual-reassembly

ip policy route-map pbr

no autostate

!

interface Vlan30

description Corporate Voice

ip unnumbered Vlan10

ip access-group allow_skinny_acl in

ip inspect voice in

no autostate

!

service-policy input mark_incoming_traffic

end

Vlan1 unassigned YES TFTP administratively down down

Vlan10 172.16.0.209 YES manual up up

Vlan20 192.168.68.1 YES manual up up

Vlan30 172.16.0.209 YES TFTP up up

I'm thinking I could create the same config with the 2951 but use the sub-interfaces like you described.

Do you think that will work?

Thanks, Pat.

Reza Sharifi · ‎09-20-2012

It should work.

I did a sample config on a 2800

interface GigabitEthernet0/1.10

encapsulation dot1Q 10

ip address 172.16.0.209 255.255.255.248

no snmp trap link-status

!

interface GigabitEthernet0/1.20

encapsulation dot1Q 20

ip address 192.168.68.1 255.255.255.0

no snmp trap link-status

!

interface GigabitEthernet0/1.30

encapsulation dot1Q 30

ip unnumbered GigabitEthernet0/1.10

no snmp trap link-status

GigabitEthernet0/1.10 172.16.0.209 YES manual up down

GigabitEthernet0/1.20 192.168.68.1 YES manual up down

GigabitEthernet0/1.30 172.16.0.209 YES TFTP up down

This interface is not connect to anything and that is why it shows it as up and down, but you get the idea.

HTH

Reza